Giorgio Leone

• Title: Rigid Orientifold Vacua in 6d with Broken SUSY

• Abstract: Brane Supersymmetry Breaking (BSB) is a phenomenon occurring in lower dimensional orientifold vacua in which supersymmetry is broken without admitting tachyonic instabilities. This feature is ascribed to the simultaneous presence of a tree-level supersymmetric closed string sector coupled with a non-supersymmetric open string one, which underlies a non-linear realisation of supersymmetry. After reviewing the original construction in six dimensions built on the T^4/Z_2 orbifold, I will present an almost rigid variation that can only be deformed via an overall D-branes recombination. Afterwards, I will describe the BSB orientifold built upon the T^4/Z_4 orbifold in which, in contrast to the previous case, the presence of fractional orientifold planes forbids any further continuous deformation. Finally, I will briefly comment on the structure of the gauge kinetic functions entering the low-energy effective action and the unitarity constraints arising from the presence of 2d defects coupled to the R-R 2-forms required by the Green-Schwarz-Sagnotti mechanism.

Antonia Paraskevopoulou

• Title: Emergence of R^4 terms in M-theory

• Abstract: In its original formulation, the Emergence Proposal postulates that terms in the low-energy effective action are emerging after integrating out towers of states becoming exponentially light in asymptotic regions of the moduli space, in agreement with the Swampland Distance Conjecture. In this talk, I will motivate an M-theoretic refinement of the Emergence Proposal by revisiting the computation of a particular higher derivative coupling in toroidal compactifications of M-theory. On a technical level, our calculations rely on employing an appropriate regularization method and demonstrate that integrating out the full towers of light states is crucial for reproducing the known amplitudes. 

• Joan Quirant

• Title: Massive spin-2 particles and the Swampland

• Abstract: In this talk, we will study swampland constraints on massive spin-2 particles coupled to gravity. We will start by considering an effective theory (EFT) with a single (interacting) massive spin-2 particle and a gap to the cutoff. We will show that this theory can never be made consistent with the so-called Classical Regge Growth conjecture (CRG), therefore being in the swampland. We will then move to the case in which there are several massive spin-2 particles in the EFT. We will see that the CRG demands an infinite tower, bounding the gaps between the masses of the different massive spin-2 particles.

• Stefano Lanza

• Title: Neural Network Learning and Quantum Gravity

• Abstract: The landscape of low-energy effective field theories stemming from string theory is too vast for a systematic exploration. However, the meadows of the string landscape may be fertile ground for the application of machine learning techniques. In this talk, I will illustrate that Quantum Gravity effective field theories are naturally endowed with key statistical learnability properties due to their underlying tame structures. Consequently, several problems therein formulated can be concretely addressed with machine learning techniques, delivering results with sufficiently high accuracy.

• Lorenzo Paoloni

• Title: On the Moduli Space Curvature at Infinity

• Abstract:  Moduli spaces are a key feature of String Compactifications and play a central role in the Swampland Programme. In this talk, I will analyse the scalar curvature of the vector multiplet moduli space of type IIA string theory compactified on a generic Calabi–Yau manifold. While the volume of this space is known to be finite, cases have been found where the scalar curvature diverges positively along trajectories of infinite distance. I will discuss the asymptotic behaviour of the scalar curvature for a broad set of large volume limits, and provide the source of the divergence both in geometric and physical terms. 

• Bernardo Fraiman

• Title: Rank Reduction in Non-supersymmetric String Theories

• Abstract: The lack of experimental evidence for supersymmetry has recently fueled a resurgence of interest in non-supersymmetric heterotic strings. A detailed analysis was carried out on the possible gauge symmetries and the behavior of the one-loop potential for circle compactifications of these strings. However, no minima were found. Orbifold compactifications lead to theories with reduced-rank symmetries and fewer moduli, making them potentially easier to stabilize. Interestingly, part of the structure underlying the supersymmetric string landscape is retained in these non-supersymmetric variants, allowing us to study these rank-reduced theories in great detail. Furthermore, an analysis of infinite distance limits reveals a complex web that interrelates both known and previously unknown theories.

• Margherita Putti

• Title: Gravitational Axiverse Spectroscopy

• Abstract:  Among various predictions of string compactifications, axions hold a pivotal role, as they provide a unique avenue to tie UV physics to experiments. Most experimental setups aim to detect a signal using the direct coupling between the axion and the Standard Model. However, string axions do not necessarily need to couple to the Standard Model directly. In this talk I will describe how inflationary models with multiple “spectator" axions coupled dark gauge sectors via Chern-Simons coupling could source observable gravitational waves. If string axions coupled to Abelian gauge fields undergo slow-roll during inflation, they produce a multi-peak GW signal whose magnitude depends on the details of the compactification. I will discuss how to embed spectator axions into type IIB orientifold compactifications and the restrictions imposed on such models from consistency and control requirements, thereby motivating models that may live in the landscape as opposed to the swampland.

• Veronica Collazuol

• Title: A twist at infinite distance in the CHL string

• Abstract: In this talk, I will analyse a space-time algebra of BPS states that emerges in the infinite distance limit in the moduli space of the nine-dimensional CHL string as the theory decompactifies to the ten-dimensional E8×E8 heterotic string, and compare it with the heterotic case. As expected, we find an affine algebra, but in a twisted version.

• David H. Wu, Harvard

• Title: Species scale in diverse dimensions

• Abstract:  In a quantum theory of gravity, the species scale can be defined as the scale at which corrections to the Einstein action become important due to the fact that the inverse of the species scale gives us the smallest size black hole described by the EFT involving only the Einstein term. In this talk, I will demonstrate the validity of this picture in diverse dimensions and with different amounts of supersymmetry and show that the species scale exhibits the expected behavior at the boundary of the moduli space. Furthermore, with this picture in mind, we can now evaluate the species scale in the interior of the moduli space along with computing the “desert point“ where the species scale is maximized, computing the diameter of the moduli space, and providing more evidence for a global bound on the gradient of the log of the species scale.

• Ignacio Ruiz, IFT Madrid

• Title: A Taxonomy of Infinite Distance Limits

• Abstract: The Emergent String Conjecture constrains the possible types of light towers in infinite-distance limits in quantum gravity moduli spaces. In this talk we will explain how one can use these to put further restrictions on the convex hull of the scalar charge-to-mass vectors of these light towers, as well as the related convex hull that controls the asymptotic behavior of the species scale. Under certain assumptions, this enables a systematic classification in terms of a finite list of polytopes. Most of these polytopes arise in known string theory compactifications, while others may yet reside in either the landscape or the swampland.

• Ethan Torres, CERN

• Title: Generalized Symmetries, Gravity, and the Swampland

• Abstract: In quantum gravity, it is generally expected that all global (generalized) symmetries are either gauged or broken. In this talk, I will discuss the UV fate of such global symmetries in the context of 7D and 5D vacua realized by compact Calabi-Yau spaces with localized singularities in M-theory. Conversely, I will also show how the emergence of (approximate) global symmetries in the IR coincides with the appearance of (approximately) topological operators realized from branes. Along the way we will see how the gluing conditions between local sectors of a Calabi-Yau lead to a preferred global structure of the non-abelian and higher-form gauge groups. In particular, we find that the 7D gauge groups always take a particular form which may suggest new swampland conditions.

• Bjoern Friedrich, Heidelberg

• Title: End-of-the-world branes in string theory and their implications in cosmology

• Abstract: The existence of end-of-the-world (ETW) branes allows for the appearance of two phenomena relevant in cosmology: The decay of universes to nothing and the creation of universes from nothing. In this talk, we discuss both the existence of ETW branes in string theory and their effects in cosmology. We explicitly construct an ETW brane for type IIB compactifications on Calabi-Yau orientifolds and estimate the decay/creation rates of universes.

• Gonzalo Villa, Cambridge

• Title: String Thermodynamics In and Out of Equilibrium: Boltzmann Equations and Random Walks

• Abstract: In this talk, we explore the Bolzmann equation approach to string thermodynamics and explore its inherent capability of studying out-of-equilibrium physics, with cosmological applications in mind. More concretely, after a short description of the phase space of string theory in a flat background, we consider the leading contribution to the decay and absorption rates of typical highly excited strings in a thermal ensemble, in an arbitrary number d of effectively non-compact dimensions (which we define in the talk). Using the random walk interpretation of these rates, which should apply in more general backgrounds, we infer more complicated contributions which at the moment lack a worldsheet computation.  All these are then used to write down Boltzmann equations in such a way that the principle of detailed balance becomes manifest, and we use this principle to find equilibrium configurations and test our inferred rates. We conclude by studying perturbations out-of-equilibrium by computing equilibration rates and fully solve for the behaviour of the perturbations in simple cases. Time permitting, potential implications in cosmology will be outlined.

• Calvin Yi-Ren Chen, Imperial

• Title: Consistency Conditions from Causality

• Abstract: In recent years, causality has emerged as a powerful criterion to distinguish between “physical” and “unphysical” low-energy effective field theories (EFTs). A direct way to ensure a given EFT is causal is to demand a lower bound on scattering time delays, which essentially imposes a speed limit averaged over a trajectory. In flat space, this is unambiguously dictated by the Minkowski light cones, but the situation is more subtle with dynamical gravity. I will make the case that the relevant notion is so-called infrared (IR) causality. 

As the prototypical example, I will study the leading-order EFT of gravity in $D \geq 5$. IR causality imposes compact bounds on its Wilson coefficient, which is consistent with positivity bounds. Attempts to further sharpen this bound use specific configurations of shockwaves which enhance the amount of causality violation. In this talk I will emphasise that this is not possible. 

This talk is based on arXiv:2112.05031 and 2309.04534 in collaboration with C. de Rham, A. Margalit, and A. J. Tolley.

• Daniel Baldwin, King's College London

• Title: Coulomb and Higgs Phases of $G_{2}$-Manifolds

• Abstract: We will discuss the physics of M-theory compactifications onto $G_2$-orbifolds of the type that can be desingularised via the method of Joyce and Karigiannis i.e. orbifolds where one has a singular locus of A1 singularities that admits a nowhere-vanishing ($\textbf{Z}_2$-twisted) harmonic 1-form. Interestingly, there are topologically distinct desingularisations of such orbifolds which we show can be physically interpreted as different branches of the 4d vacuum moduli space of the arising gauge theories, known as ‘Coulomb’ and ‘Higgs’ branches. The results suggest generalisations of the results of Joyce and Karigiannis to $G_2$-orbifolds with more diverse ADE singularities and higher order twists. 

As a bonus, we also get an isomorphism between the moduli space of flat connections on flat compact 3-manifolds and the moduli space of Ricci flat metrics on the $G_{2}$-orbifolds. We will briefly discuss this. Based on 2309.12869 and 2312.12311.

• Jesús Huertas, IFT Madrid

• Title: Aspects of Dynamical Cobordism in AdS/CFT

• Abstract: The cobordism conjecture implies that consistent theories of  Quantum Gravity must admit the introduction of boundaries. In this talk, we will present the dynamical realization of the cobordism conjecture in type IIB in AdS5 × S5, using the existing gravity duals of 4d N=4 SYM with Gaiotto-Witten superconformal boundary conditions (near-horizon limits of D3-branes ending on NS5- and D5-branes). We will show that these configurations are, from the 5d perspective, dynamical cobordism solutions which start from an asymptotic AdS5 vacuum and evolve until they hit an end of the world (ETW) brane with AdS4 worldvolume. The latter displays localization of gravity, and provide a string theory completion of the Karch-Randall AdS branes. Also, a novel double scaling limit will be presented, which zooms into the ETW brane and makes localization of gravity manifest, and which shows a tantalizing relation with wedge holography. Finally, we will briefly explain how to extend the picture to AdS5 theories with less (super)symmetry, via orbifolds and S-folds, leading to dynamical cobordisms for gravity duals of 4d theories with N=2 and N=3 supersymmetry.

• Hamza Ahmed, Northeastern University

• Title: T-duality and flavor symmetries of Heterotic Little String Theories(LSTs)

• Abstract: 6D Heterotic Little String Theories(LSTs) are a subsector of every 6D SUGRA (with at least one tensor multiplet), after decoupling gravity. As such, while possessing usual QFT-like properties such as global symmetries, they also possess gravity-like properties such as T-duality, which makes them an interesting intermediate. Recently, a fruitful line of research has been to chart the landscape of T-dual LSTs, and establish certain invariants across this T-duality, which includes the 5D Coulomb branch dimension, and the 2-Group structure constants (mixed anomalies). In this talk, we will argue that the rank of the flavor algebra is another invariant across this duality. This involves using 6D anomaly cancellation conditions and carefully taking into account potential ABJ anomalies. We will then discuss some interesting novel LSTs with non-trivial flavor holonomies, focusing on their T-duality structure. Based on arXiv:2311.02168.

• Filippo Revello, Utrecht University

• Title: String Theory and the First Half of the Universe

• Abstract: We perform a detailed study of stringy moduli-driven cosmologies between the end of inflation and the commencement of the Hot Big Bang, including both background and cosmological perturbations:  a period that can cover half the lifetime of the universe on a logarithmic scale. Compared to the standard cosmology, stringy cosmologies motivate extended kination, tracker and moduli-dominated epochs involving significantly trans-Planckian field excursions. As conventional effective field theory is unable to control Planck-suppressed operators, such epochs require a stringy completion for a consistent analysis. Perturbation growth is substantially enhanced compared to conventional cosmological histories.  The transPlanckian field evolution results in radical changes to Standard Model couplings during this history and we outline potential applications to baryogenesis, dark matter and gravitational wave production.

• Jeroen Monnee, Utrecht University

• Title: Complexity of the Flux Landscape

• Abstract: The landscape of F-theory flux compactifications is expected to be remarkably constrained due to deep insights in Hodge theory and tame geometry. In this talk, I will first review known finiteness theorems for the landscape of self-dual flux vacua and provide additional insights on this matter using asymptotic Hodge theory. In the remainder of the talk, I will present and motivate three new mathematical conjectures on the enumeration, dimensionality, and geometric complexity of the flux landscape, including a reformulation of the tadpole conjecture. Based on Arxiv:2311.09295.

• Muthusamy Rajaguru, Lehigh University

• Title: Moduli stabilization in type IIB models with h^{1,1}=0

• Abstract: The tadpole conjecture constrains the number of moduli that can be stabilized with fluxes in F-theory and type IIB flux compactifications. In this talk, I will discuss ongoing work that aims to test this assertion in non-geometric type IIB flux compactifications with no Kähler moduli. In particular, I will restrict to supersymmetric Minkowski vacua in orbifolds of the 1^9 and 2^6 Gepner models. Generically these Minkowski critical points have many massless directions. In principle, we are able to expand the flux superpotential around these Minkowski critical points upto arbitrary order. This allows us to ask if these massless directions are truly flat or if they get stabilized by some higher-than-quadratic order term in the superpotential. Furthermore, there exist powerful non-renormalization theorems for the flux superpotential that make such questions meaningful to ask in these non-geometric compactifications. 

• Rafael Álvarez-García, Hamburg University

• Title: The Distance Conjecture in F-theory via Semi-stable Degenerations

• Abstract: We study infinite-distance limits in the complex structure moduli space of six-dimensional F-theory as part of the ongoing efforts to understand the boundaries of moduli spaces in quantum gravity. Our work consists of two parts: an algebro-geometric analysis of the limits, corresponding to the recent paper arXiv:2310.07761, and their physical interpretation, to appear soon. We start by summarizing the first of these, explaining how the limits can be described as semi-stable degenerations of elliptic Calabi-Yau threefolds, leading to an asymptotic spacetime consisting of log Calabi-Yau spaces glued along their boundaries. We then center our attention on the physical interpretation of the infinite-distance trajectories as either emergent string limits or partial decompactification processes to theories with (non-perturbative) defects. The latter aspect is a novel feature of the six-dimensional scenario compared with its counterpart in compactifications of F-theory on elliptic K3 surfaces.

• Alberto Castellano, IFT

• Title: A Universal Pattern in Quantum Gravity

• Abstract: The Distance Conjecture in the Swampland program famously predicts the breakdown of any low energy EFT description of a gravitational theory when probing infinite distance/weak coupling points in the moduli space due to the appearance of an infinite number of states with exponentially light masses. Such universal breakdown can be made more precise upon introducing the Quantum Gravity cut-off, which sets the maximal energy scale of any underlying field theoretic description, and which can be seen to also decrease exponentially with the traversed field space distance. In this talk, we will argue for a sharp and universal pattern linking these two quantities and which is moreover satisfied at any infinite distance boundary of moduli space, thus imposing non-trivial 'gluing' conditions for the different phases (or duality frames) of the theory. In addition, we will also explain what are the minimal sufficient conditions for it to hold from the bottom-up perspective, as well as the derived bounds that immediately follow from the pattern.

• George Tringas, LAPTH

• Title: On the robustness of scale-separated AdS4 from type IIA

• Abstract: In this presentation, I will discuss an extension of the so called DGKT solution resulting from the O6 plane backreaction. Our focus will center on a well-established large N expansion method that allows us to identify corrections to fields and flux profiles due to backreaction, thereby refining the smeared DGKT solution. The parameter N represents the unbounded F4 flux parameter. We will investigate this extension within the framework of ten-dimensional massive type IIA supergravity and a four-dimensional effective theory, utilizing a warped compactification framework. Our analysis will encompass the generalization of flux scaling and the exploration of potential contributions from backreaction corrections, including axions. We will discuss the relevance of corrections to the DGKT scalar potential and determine whether they dominate over alpha prime corrections. Additionally, we will consider flux quantization, which imposes crucial constraints on flux corrections. Our investigation extends to the examination of next-to-next-to-leading-order corrections and their implications. This presentation will be based on the recent paper 2310.06115.

• Daniel Panizo, Uppsala University

• Title: A cosmological excursion to dark bubbles

• Abstract: The Dark Bubble scenario proposes that an expanding four-dimensional cosmology, equipped with dark energy, can be realised on the boundary of a five-dimensional bubble mediating the decay between two non-supersymmetric anti-de Sitter vacua. In this express journey, I will be your guide to the bulk, where dark bubbles can nucleate and expand. We will depart from string theory at around 11:30 EST, all the way down to four dimensions. The required technology to appreciate the energy scale hierarchy of the model will be provided when crossing the junction conditions border (No need to bring small extra dimensions from home). Stringy corrections will ensure our safe landing on universes with positive cosmological constant. Here we will study the Gauss-Codazzi interplay between the bubble's boundary and bulk, which decorates the expanding cosmology with familiar energy densities, such as gravitational or electromagnetic radiation.

• Salvatore Raucci, Scuola Normale Superiore Pisa

• Title: A first-order formalism for non-supersymmetric strings

• Abstract: The absence of supersymmetry in perturbative string theory usually leads to runaways arising from nonvanishing dilaton tadpoles. The spacetime manifestation is a scalar potential, the stringy counterpart of quantum vacuum energies in quantum field theory, which should be accounted for in geometric vacua. In this talk, I will discuss a first-order formalism that replaces supersymmetry as a vacuum-generating technique for non-supersymmetric strings. In its most basic form, this is known as fake supersymmetry.  This strategy raises interesting observations on vacuum stability by employing a definition of energy inspired by the Witten-Nester approach.

• Matilda Delgado, IFT

• Title: Emergence of Species Scale Black Hole Horizons

• Abstract: The scale at which quantum gravitational effects become manifest, the species scale, has recently been argued to take values parametrically lower than the Planck scale. It is therefore of interest to quantum gravity phenomenology to have a precise definition of how to compute this scale in any EFT that has a UV completion in quantum gravity. Two proposals have been made in the litterature, of different conceptual origin; one linked to the size of the smallest black hole that one can describe in an EFT and the other to the scale of higher-derivative corrections to the EFT. Arguably one of the most profound aspects of a theory of quantum gravity is that it should be background independent and that semi-classical spacetime should only "emerge" as a low-energy description. I will demonstrate how this notion of "emergence" unites the two definitions of the species scale. I will do so by studying small (singular) black hole solutions in string theory and illustrating how higher-derivative corrections obtained from emergence correct these solutions and generate a species scale sized horizon for these black holes. Based on arXiv:2310.04488.

• Nicolò Petri, Ben Gurion U. of Negev

• Title: Towards AdS Distances in String Theory

• Abstract: Recent developments in high-energy physics have brought to light the need to formulate a consistent notion of distance between gravitational vacua. Specifically, within the Swampland program, the AdS Distance conjecture proposes to assign such a notion for AdS vacua in quantum gravity. Beginning with very basic AdS vacua in string theory, I will expand upon this concept, providing a more formal framework for it. Firstly, I will introduce a precise definition of a metric for the space of conformal variations of AdS. This metric, however, turns out to be negative, resulting in an ill-defined distance, a property related to the famous conformal factor problem in quantum gravity. Nonetheless, in string theory, variations in the AdS conformal factor are accompanied by variations in the internal dimensions and background flux. Interestingly, the inclusion of these variations can change the sign of the metric over the space of AdS vacua variations. I will propose a consistent procedure for deriving the distance between AdS vacua by introducing the notion of an "action metric", which accounts for all of these variations simultaneously. I will test this procedure by focusing on AdS4 and AdS7 Freund-Rubin vacua in M-theory and demonstrate that it yields a well-defined and positive distance.

• Matteo Licheri, University of Bologna

• Title: Higher Derivative Corrections to String Inflation

• Abstract: We quantitatively estimate the leading higher derivative corrections to N=1 supergravity derived from IIB string compactifications and study how they may affect moduli stabilisation and LVS inflation models. Using the Kreuzer-Skarke database of 4D reflexive polytopes and their triangulated Calabi-Yau database, we present scanning results for a set of divisor topologies corresponding to threefolds with 1≤ h^1,1 ≤ 5. In particular, we find several geometries suitable to realise blow-up inflation, fibre inflation and poly-instantons inflation, together with a classification of the divisors topologies for which the leading higher derivative corrections to the inflationary potential vanish. In all other cases, we instead estimate numerically how these corrections modify the inflationary dynamics, finding that that they do not destroy the predictions for the main cosmological observables.

• Muldrow Etheredge, UMass 

• Title: Dense Geodesics, Tower Alignment, and the Sharpened Distance Conjecture

• Abstract: The Sharpened Distance Conjecture and Tower Scalar Weak Gravity Conjecture are closely related but distinct conjectures, neither one implying the other. Motivated by examples, I propose that both are consequences of two new conjectures: 1. The infinite distance geodesics passing through an arbitrary point φ in the moduli space populate a dense set of directions in the tangent space at φ. 2. Along any infinite distance geodesic, there exists a tower of particles whose scalar-charge-to-mass ratio (-∇ log m) projection everywhere along the geodesic is greater than or equal to 1/\sqrt(d-2). I perform several nontrivial tests of these new conjectures in maximal and half-maximal supergravity examples. I also use the Tower Scalar Weak Gravity Conjecture to conjecture a sharp bound on exponentially heavy towers that accompany infinite distance limits. Based on 2308.01331.

•  Carlo Branchina, Chung-Ang University

• Title: UV-sensitivity in Kaluza Klein Theories: Naturalness and Dark Dimension

• Abstract: When the Higgs potential or the vacuum energy are derived in the framework of Higher dimensional effective field theories on a multiply connected spacetime with compact dimensions and non-trivial boundary conditions (as in the case of the Scherk-Schwarz SUSY breaking), the usual calculations lead to the conclusion that these quantities are naturally UV-insensitive. By means of a thorough analysis of the assumptions on which these calculations are based, I will show that this paradigm actually misses a crucial source of UV-sensitivity, ultimately connected to the non-trivial topology of the spacetime in these theories. As a consequence, the conclusions on the UV-insensitivity of the Higgs mass, of the Higgs potential, and on the existence of a Dark Dimension (that crucially depends on the supposed UV-insensitivity of the vacuum energy in Kaluza-Klein theories) need to be seriously reconsidered. Our results were challenged in a note very recently posted online. If time allows, I will point out the flaws in these criticisms. 

• Junsei Tokuda, IBS

• Title: Gravitational positivity bounds: implications for the swampland program

• Abstract: In the context without gravity, it has been known that the S-matrix positivity bounds offer a useful tool to derive ultraviolet constraints on low-energy effective field theories. In this talk, we assume that the positivity bounds are approximately valid even in the presence of gravity, and discuss the implications of the bounds for phenomenological models. Interestingly, we obtain strong bounds on the simplest dark photon models which can be compared with experimental bounds, while the Standard Model easily satisfies the bounds. We also provide a scenario which gives rise to the approximate gravitational positivity bounds based on the Reggeization of graviton exchange. 

• Manki Kim, MIT

• Title: Towards string loop corrections in Calabi-Yau orientifold compactifications

• Abstract: Computation of string loop corrections to the effective action has been one of the main challenges in string phenomenology. One major complication for such computations is that the string loop corrections are sensitive to the spectrum of strings probing Calabi-Yau orientifolds, which is practically inaccessible. In this talk, I will claim that some terms in the string one loop corrections to the Kahler potential are computed by more computable crude details of the string spectrum. This result may pave a way to explicit computations of the string loop corrections in generic Calabi-Yau orientifold compactifications.

• Houri-Christina Tarazi, Harvard

• Title:  Non-BPS path to the string lamppost

• Abstract: We provide further motivation for the string lamppost principle in 9d supergravities. Using a blend of ideas which includes Swampland conjectures, finiteness of black hole entropy, and classification of SCFTs, we show that infinite distance limits that keep BPS states heavy must decompactify to type IIA supergravity on an interval. Without relying on string theory, we provide bottom-up explanations for various UV features of the theory, such as the physics near the orientifold branes and the worldvolume theories of different stacks of non-perturbative 8-branes. We also provide a Swampland argument for the countability of the number of inequivalent string limits up to dualities which is a strong result with applications beyond this work.
  
  

•  Christian Kneißl, Max Planck Institute Munich

• Title: Dynamical Cobordism Conjecture: Solutions for End-of-the-World Branes

• Abstract: Analyzing finite size solutions for a generalized D-dimensional Dudas-Mourad (DM) model reveals a dynamical cobordism configuration with neutral and charged end-of-the-world (ETW) defect branes. In this talk I will demonstrate an explicit construction of non-isotropic solutions of the corresponding codimension one ETW-branes. Consequently, I will show the appearance of a lower bound for the critical exponent in the scaling behavior of the distance and the curvature close to the defect. This allows us to make a connection to the (sharpened) Swampland Distance Conjecture and the (Anti-) de Sitter Distance Conjecture.

• Héctor Parra de Freitas, IPhT

• Title:  Tadpoles and Gauge Symmetries

• Abstract: The tadpole conjecture proposes that complex structure moduli stabilisation by fluxes that have low tadpole charge can be realised only at special points in moduli space, leading generically to (large) gauge symmetries. In this talk I will consider F-Theory flux compactifications on K3xK3 with fully stabilised complex structure moduli and show how lattice embedding techniques allow for a full characterization of their gauge symmetries. I will report on the results of a scan of these models, showing that all of them have non-abelian gauge symmetries whenever the tadpole bound is satisfied.
  
  

• Min-Seok Seo, KNUE

• Title: Uplift and towers of states in warped throat

• Abstract: The difficulty in realizing the metastable de Sitter vacuum in the string model has been considered in light of the distance conjecture. In this talk, we investigate the Type IIB compactifications containing the warped throat and point out that the uplift potential produced by anti-D3 branes satisfies the scaling behavior with respect to the tower mass scale, hence can be directly connected to the distance conjecture. Unless the throat length is extremely close to zero, the tower mass scale corresponds to the Kaluza-Klein mass, the lowest tower mass scale.

• Simon Schreyer, University of Heidelberg 

• Title:  α' Corrections to KPV: An Uplifting Story

• Abstract: In earlier work, the effect of $\alpha'^2$ curvature corrections on the NS5-brane responsible for the decay of anti-D3-branes in the set-up of Kachru, Pearson, and Verlinde (KPV) was considered. In this talk, I extend this analysis to include all known $\alpha'^2$ corrections to the action of an abelian fivebrane which involve not just curvature but also gauge fields and flux. This leads to the $\alpha'^2$ corrected potential for the NS5-brane at the tip of the Klebanov-Strassler throat. The resulting potential provides the explicit realization of a novel uplifting mechanism where one can obtain metastable vacua with an arbitrarily small positive uplifting potential by fine-tuning $\alpha'$ corrections against the tree-level potential. This mechanism works for small warped throats, both in terms of size and contribution to the D3-tadpole, thereby sidestepping the issues associated with a standard deep warped throat uplift which are deadly in KKLT and severely constraining in the Large Volume Scenario.
  
  

• Flavio Tonioni, University of Wisconsin-Madison

• Title: Late-time Accelerating Cosmologies

• Abstract: I will characterize the late-time expansion rate of the universe in multi-scalar cosmologies with multi-exponential potentials, taking advantage of previously unobserved universal asymptotic features of the solutions to the cosmological equations. This provides a simple diagnostic of whether any given multi-exponential potential holds the necessary conditions for late-time cosmic acceleration. I will also discuss the conditions under which scaling solutions are inevitable late-time cosmological attractors for such theories. For scaling cosmologies, all field-space trajectories are known analytically, which allows one to characterize exactly any observable of interest. Multi-exponential potentials have been studied extensively as phenomenological models of quintessence and, moreover, they are ubiquitous in string-theoretic constructions. I will therefore sharpen several statements on the low-energy signatures of quantum gravity in this context. [based on hep-th/2303.03418 + upcoming preprint, in collaboration with G. Shiu and H.V. Tran]

• Roberta Angius, IFT Madrid

• Title: Small Black Hole Explosions

• Abstract: 4d small black holes are powerful tools to pursue dynamical explorations of infinite distances in moduli space. Upon S2 compactification they show the features of a Dynamical Cobordism, with a singular core, located at finite distance in spacetime, at which some scalars run to infinity.
  In this talk, I will discuss such setups in the presence of additional 4d scalar potentials growing exponentially near the black hole core with a characteristic exponent δ. I will show that the small black hole behavior is preserved for values of δ under a certain limit, while up to this bound the potential is too large, it obstructs the realisation of the Dynamical Cobordism, and the small black hole explodes into a puffed-up regular black hole or into a runaway configuration. I will emphasize as the 2d perspective puts the black hole and the scalar potentials on an equal footing, allowing us a direct analysis of their competition.
  In order to describe an explicit realisation of this mechanism I will focus on the context of 4d N = 2 gauged supergravity theories where the 2d picture also allows a unified discussion of fluxes, domain walls and black holes.
  Finally I will discuss the capability of small black holes to continue exploring infinite distance limits in moduli space, even in the presence of 4d potentials.
  
  

• Ignacio Ruiz, UAM Madrid

• Title: Asymptotic Accelerated Expansion in String Theory and the Swampland

• Abstract: We study whether the universal runaway behaviour of stringy scalar potentials towards infinite field distance limits can produce an accelerated expanding cosmology à la quintessence. We identify a loophole to some proposed bounds that forbid such asymptotic (at parametric control) accelerated expansion in 4d $\mathcal{N}=1$ supergravities, by considering several terms of the potential competing asymptotically. We then analyse concrete string theory examples coming from F-theory flux compactifications on Calabi-Yau fourfolds, extending previous results by going beyond weak string coupling to different infinite distance limits in the complex structure moduli space. We find some potential candidates to yield asymptotic accelerated expansion with a flux potential satisfying $\gamma=\frac{\|\nabla V\|}{V}<\sqrt{2}$ along its gradient flow. However, whether this truly describes an accelerated expanding cosmology remains as an open question until full moduli stabilization including the Kahler moduli is studied. Finally, we also reformulate the condition for forbidding asymptotic accelerated expansion as a convex hull de Sitter conjecture which resembles a convex hull scalar WGC for the membranes generating the flux potential. This provides a pictorial way to quickly determine the asymptotic gradient flow trajectory in multi-moduli setups and the value of $\gamma$ along it.

• Jacob Leedom, DESY

• Title: Heterotic de Sitter Beyond Modular Symmetry

• Abstract: I will discuss the vacua of 4d heterotic toroidal orbifolds using effective theories consisting of an overall Kähler modulus, the dilaton, and non-perturbative corrections to both the superpotential and Kähler potential that respect modular invariance. I will prove three de Sitter no-go theorems for several classes of vacua and thereby substantiate and extend previous conjectures. Additionally, I will provide evidence that extrema of the scalar potential can occur inside the PSL(2, Z) fundamental domain of the Kähler modulus, in contradiction of a separate conjecture. I will also illustrate a loophole in the no-go theorems and determine criteria that allow for metastable de Sitter vacua. Finally, I will identify inherently stringy non-perturbative effects in the dilaton sector that could exploit this loophole and potentially realize de Sitter vacua.
  
  

• Niccolò Cribiori, Munich

• Title: Swampland constraints on scale separation and de Sitter in 4D & 5D

• Abstract: Swampland conjectures are meant to be consistency conditions for low energy effective theories to be compatible with quantum gravity. In the talk, I will argue that applying some of the most tested conjectures, such as the weak gravity conjecture, directly to gauged supergravity with at least eight supercharges leads to stringent constraints. In particular, one can argue for the absence of supersymmetric anti-de Sitter vacua with a separation of scales between the compact and the non-compact dimensions. At the cost of introducing an additional assumption on the gravitino mass, a similar analysis can be extended to de Sitter vacua as well.

• Sebastian Rauch, UMass

• Title: Symmetries and Structures of N=3 S-folds

• Abstract:  I will discuss the techniques and results of computing the global structures and symmetries of N=3 S-folds. We may treat a stack of D3 branes probing an S-fold holographically, and compute the symmetries of the N=3 SCFT via topological information in the bulk. I will proceed by reviewing S-folds and the role branes play as symmetry operators. I will then compute the possible global structures and symmetries of N=4 and 3 S-folds, the N=4 S-folds providing a check of our methods.
  
  

• Lorenz Schlechter, Utrecht

• Title: Tameness in QFT and CFT

• Abstract: In this talk I will discuss tameness as a finiteness principle that can be applied to a variety of physical systems. Specifically, I will introduce the concept of tame geometry and explore its application to both perturbative and non-perturbative quantum field theories. Through an examination of solvable models, I will offer evidence to support tameness as a swampland criterion, and put forth precise conjectures regarding the tameness of amplitudes, as well as the spaces of QFTs and CFTs.

• Saghar Sophie Hosseini, Durham

• Title: Symmetry TFTs of geometrically engineered field theories

• Abstract: (D+1)-dimensional topological field theories, known as SymTFTs, contain information about choices of generalised global symmetries and anomalies of D-dimensional QFTs. In this talk, I will introduce SymTFTs and explain how the BF theory, classifying higher-form symmetries, may be obtained from the dimensional reduction of a Chern-Simons action for self-dual fields in string theory.

• Eduardo Garcia-Valdecasas, Harvard

• Title: Non invertible symmetries in supergravity

• Abstract: We revisit the symmetries of maximal supergravity in 10d and 11d, showing that there are non-invertible symmetries analog to the ones present in 4d theories with a U(1) symmetry with ABJ anomaly. As expected, these symmetries are explicitly broken by the UV completion, String Theory or M-theory. The way in which they are broken gives further support to the connection between the completeness hypothesis and the absence of global symmetries in gauge theories.

• Alessandro Mininno, DESY

• Title: The Asymptotic Weak Gravity Conjecture in M-theory 

• Abstract:  In this talk, I will focus on five-dimensional compactifications of M-theory on Calabi-Yau 3-folds. In particular, for gauge groups with a weak coupling limit, I will show that there exist many super-extremal states along every ray in the charge lattice, as predicted by the tower Weak Gravity Conjecture, for any consistent quantum gravity theory.
  I will first characterize the possible weak coupling limits, building on an earlier classification of infinite distance limits in the Kähler moduli space of M-theory compactifications.
  The result is that weakly coupled gauge groups are associated to curves on the compactification space contained in generic fibers or in fibers degenerating at finite distance in their moduli space. These always admit an interpretation as a Kaluza-Klein or winding U(1) in a dual frame or as part of a dual perturbative heterotic gauge group, in agreement with the Emergent String Conjecture. Finally, the fact that every ray in the associated charge lattice either supports a tower of BPS or of non-BPS states, can be shown using the connection between Donaldson-Thomas invariants and Noether-Lefschetz theory, proving also that these states satisfy the super-extremality condition, at least in the weak coupling regime.
  
  

• Alberto Castellano Mora, Madrid

• Title: How can Gravity Emerge?

• Abstract: In the Emergence Proposal in QG it is conjectured that all light-particle kinetic terms are absent in the fundamental UV theory and are generated by quantum corrections in the IR. It has been argued that this proposal may provide for some microscopic understanding of the Weak Gravity and the Swampland Distance conjectures. In this talk, we will review the main motivations behind this surprising idea, elaborating on certain string/M-theory examples which exhibit this phenomenon along infinite distance corners of their moduli spaces. This renders support to the Emergence Proposal, and to the idea that infinite distance singularities may arise in QG as an intrinsic IR phenomenon.

• Nicklas Ramberg, Mainz 

• Title: Bubbles from Dark Confinement with Holography

• Abstract:  Gravitational waves emitted from strongly coupled QFTs are, at present, a daunting task to accurately predict due to the strong coupling. In this talk, we demonstrate how to predict the gravitational wave spectra of such theories using holography and lattice data input  for a pure SU(3) Yang-Mills theory with minor uncertainties. We will elaborate on how we obtain an effective potential using holography with the free energy landscape approach and formulate an effective action. Once the effective action is in our grasp, we will use this to study bubble nucleation to predict the gravitational wave spectra.
  
  

• Shing Yan Li, MIT

• Title: Large U(1) charges from flux breaking in 4D F-theory models

• Abstract: We study the massless charged spectrum of U(1) gauge fields in F-theory that arise from flux breaking of a nonabelian group. The U(1) charges that arise in this way can be very large. In particular, using vertical flux breaking, we construct an explicit 4D F-theory model with a U(1) decoupled from other gauge sectors, in which the massless/light fields have charges as large as 657. This result greatly exceeds prior results in the literature. We argue heuristically that this result may provide an upper bound on charges for light fields under decoupled U(1) factors in the F-theory landscape.

• Matilda Delgado, IFT Madrid 

• Title: Black Holes as Probes of Moduli Space Geometry

• Abstract:  We argue that supersymmetric BPS states can act as efficient finite energy probes of the moduli space geometry thanks to the attractor mechanism. We focus on 4d N=2  compactifications and capture aspects of the effective field theory near the attractor values in terms of physical quantities far away in moduli space. Furthermore, we illustrate how the standard distance in moduli space can be related asymptotically to the black hole mass. We also compute a measure of the resolution with which BPS black holes of a given mass can distinguish far away points in the moduli space. The black hole probes may lead to a deeper understanding of the Swampland constraints on the geometry of the moduli space.
  
  

• Yichul Choi, Stony Brook

• Title: Non-invertible Gauss Law and Axions

• Abstract: In axion-Maxwell theory, there is no conserved, gauge-invariant, and quantized electric charge. This is related to the absence of the ordinary electric 1-form symmetry. Instead, I will explain that the theory has a non-invertible version of the electric 1-form symmetry and discuss a non-invertible Gauss law associated with it. This non-invertible 1-form symmetry leads to exact selection rules for correlation functions of extended operators, which are related to the Witten effect. Finally, I will comment on the implication of the non-invertible symmetry for the Completeness Hypothesis in quantum gravity.

• Luca Nutricati, Durham 

• Title: On the running of gauge couplings in string theory

• Abstract:  String theories naturally give rise to infinite towers of states whose degeneracies grow exponentially as functions of mass. These infinite towers of states are ultimately responsible for many of the finiteness properties for which string theory is famous. Recently, a framework was developed in which the effects of all of these states can be incorporated in a self-consistent way when calculating quantities relevant for low-energy phenomenology, such as the masses of the Higgs fields that arise in such theories. This formalism also gives rise to an "on-shell'' effective field theory description in which the final results are expressed in terms of contributions from only the on-shell, level-matched physical string states, and in which these quantities also exhibit an EFT-like "running'' as a function of an effective spacetime mass scale. In this talk, I’ll discuss how to apply this formalism to calculate the running of the gauge couplings within closed string theories. Unlike previous calculations in the literature, our calculation fully respects the underlying closed-string modular invariance and expresses many of the final results in terms of contributions from only the on-shell physical string states. We find, however, that the calculation of the gauge couplings differs in one deep way from the calculation of the Higgs mass:  while the latter results depend on the supertraces over only the on-shell string states, the former results have a different modular structure which causes them to depend on supertraces over the off-shell string states as well.
  Taken together, our results yield the expected logarithmic running of the gauge couplings at certain energy scales. However, they also yield a number of intrinsically stringy behaviors that transcend what might be expected within an effective field theory approach.
  
  

• Muyang Liu, Uppsala

• Title: Geometry and T-dualities between Heterotic ALE instantonic Little String Theories

• Abstract: Recently, we revisited the properties of Heterotic string compactifications on ALE space in a series of papers. In particular, this talk focuses on the geometric counterpart of T-dualities between Heterotic ALE instantonic LSTs in F-theory. T-dualities are realized as inequivalent elliptic fibrations of the same geometry. Due to the Heterotic/F-theory duality, the elliptic fibered Calabi-Yau in our consideration admits a nested elliptic K3 fibration structure. This is crucial to our design: the K3 fibrations determine the flavor groups and their global forms, in addition to serving as the key to identifying various T-dualities. In the end, I will also comment on more generic LSTs originating from non-geometric Heterotic backgrounds: a particularly exotic class of LSTs formed from extremal K3 surfaces that allows flavor groups with a maximal rank of 18. We find that all models are related to a so-called T-hexality (i.e., a 6-fold family of T-dualities) that we anticipate from the inequivalent elliptic fibrations of the extremal K3.

• Luca Melotti, IFT, Madrid

• Title: EFT strings and emergence

• Abstract:  We revisit the Emergence Proposal in 4d N = 2 vector multiplet sectors that arise from type II string Calabi–Yau compactifications, with emphasis on the role of axionic fun- damental strings, or EFT strings. We focus on large-volume type IIA compactifications, where EFT strings arise from NS5-branes wrapping internal four-cycles, and consider a set of infinite-distance moduli-space limits that can be classified in terms of a scaling weight w = 1, 2, 3. It has been shown before how one-loop threshold effects of an infinite tower of BPS particles made up of D2/D0-branes generate the asymptotic behaviour of the gauge kinetic functions along limits with w = 3. We extend this result to w = 2 limits, by taking into account D2-brane multi-wrapping numbers. In w = 1 limits the leading tower involves EFT string oscillations, and one can reproduce the behaviour of both weakly and strongly-coupled U(1)’s independently on whether the EFT string is critical or not, by assuming that charged modes dominate the light spectrum. 

• Nicolas Kovensky, IPhT, Saclay

• Title: More on KKLT from ten dimensions

• Abstract:  Gaugino condensation on D-branes wrapping internal cycles give a mechanism to stabilize the associated moduli. According to the effective field theory, they can give rise, when combined with fluxes, to supersymmetric AdS$_4$ solutions. In this talk we provide a ten-dimensional description of these vacua. We first describe the supersymmetry equations for type II AdS$_4$ vacua non-perturbative sources in the framework of generalized complex geometry. We then solve them for type IIB compactifications with gaugino condensates on smeared D7-branes. The solution is remarkably simple. Supersymmetry requires a (conformal) Calabi-Yau manifold and self-dual three-form fluxes with an additional (0,3) component. The latter is  proportional to the cosmological constant, whose magnitude is determined by the expectation value of the gaugino condensate and the stabilized volume of the cycle wrapped by the branes. This confirms, qualitatively and quantitatively, the results obtained using effective field theory. As for the localized solution, it requires going beyond SU(3)-structure internal manifolds. If time allows, we show that the action can nevertheless be evaluated on-shell without relying on the details of such complicated configuration, and discuss the issue of divergencies arising in this context.

•  Stefano Andriolo, Ben Gurion

• Title: Self-Binding in AdS and the WGC,

• Abstract:  The Positive Binding Conjecture is a proposed formulation of the Weak Gravity Conjecture appropriate to Anti de-Sitter (AdS) space. It proposes that in a consistent gravitational theory, with a U(1) gauge symmetry, there must exist a charged particle with non-negative self-binding energy. In order to formulate this as a constraint on a given effective theory, we calculate the self-binding energy for a charged particle in AdS4 and AdS5. In particular, we allow it to couple to an additional scalar field of arbitrary mass. Unlike the flat-space case, even when the scalar field is massive it contributes significantly to the binding energy, and therefore is an essential component of the conjecture. In AdS5, we give analytic expressions for the self-binding energy for the cases when the scalar field is massless and when it saturates the Breitenlohner-Freedman (BF) bound, and in AdS4 when it is massless. We show that the massless case reproduces the flat-space expressions in the large AdS radius limit, and that both analytic cases lead to vanishing total self-binding energy for BPS particles in example supersymmetric models. For other masses of the scalar we give numerical expressions for its contribution to the self-binding energy. 

• Eduardo Gonzalo, Lehigh U.

• Title: Dark Dimension Gravitons as Dark Matter

• Abstract:  We consider cosmological aspects of the Dark Dimension (a mesoscopic dimension of micron scale), which has recently been proposed as the unique corner of the quantum gravity landscape consistent with both the Swampland criteria and observations. In particular we show how this leads, by the universal coupling of the Standard Model sector to bulk gravitons, to massive spin 2 KK excitations of the graviton in the dark dimension (the "dark gravitons") as an unavoidable dark matter candidate. We explain the main features of the model and comment on future experiments that can probe the dark dimension scenario. 

• Patrick Jefferson, MIT

• Title: Analyzing the non-perturbative superpotential in type IIB orientifold compactifications

• Abstract: In 4D N=1 type IIB orientifold compactifications, non-perturbative contributions to the superpotential can be generated by D3-instantons or seven-brane gaugino condensation. Under M/F-theory duality, these contributions are known to have a common origin, namely Euclidean M5-instantons wrapping vertical divisors in an elliptic Calabi-Yau fourfold. Understanding the geometric properties of vertical divisors is essential to analyzing the moduli-dependence of the non-perturbative superpotential. I will discuss a newly-developed algorithm for computing the Hodge structure of vertical divisors, which only requires as input the geometric data of the corresponding type IIB orientifold compactification space. A key part of this algorithm is a conjectured formula for the Euler characteristic of vertical divisors that captures the contributions of O3-planes. 

• Hao Zhang, UPenn

• Title: The Branes Behind Generalized Symmetry Operators

• Abstract:  Generalized global symmetries in a QFT are encoded in topological symmetry operators, which non-trivially link the defect operators. In QFTs engineered via string theory on a non-compact geometry X, these defects descend from branes wrapped on non-compact cycles which extend to the boundary \partial X. Yet the realization of symmetry operators via string construction has long been implicit. We construct the generalized symmetry operators linking these defects as arising from magnetic dual branes wrapped on cycles in \partial X. This provides a systematic way to study their worldvolume topological field theories, and the resulting fusion rules. We illustrate these general features in the context of 6D superconformal field theories constructed using the F-theory, and read off the worldvolume theory of the symmetry operators from wrapped branes. These systems generically have non-invertible 2-form symmetries whenever the duality bundle of the F-theory model is non-trivial. We conclude by remarking that our understanding in principle allows for identifying the full symmetry structure of general geometrically engineered QFTs as (higher) fusion categories. We also comment on the potential top-down understanding of such categorical structure in connection with D-branes in topological string theories.

• Vincent Van Hemelryck, KU Leuven

• Title: Scale-separated AdS3 vacua from G2-orientifolds using bispinors

• Abstract: In this talk, I discuss minimal supersymmetric AdS3 solutions on G2-orientifolds of type IIA and IIB supergravity. Such solutions have been studied before and I show that they can easily be obtained by  bispinor techniques. With this formalism, I show that AdS3 solutions in massless type IIA string theory do not exist on such G2-backgrounds. Moreover, I show that in massive type IIA, the vacua do admit a separation of scales, whereas the same cannot be said for the type IIB. Furthermore, I present a formula for the 3d superpotential in terms of the bispinors, valid for both type IIA and IIB configurations. Finally, I show that the supersymmetry conditions for this superpotential lead back to the bispinor equations. 

• Lea Bottini,  University of Oxford.

• Title: Non-Invertible Symmetries from Outer-Automorphism Gaugings

• Abstract: In the past year, a lot of attention has been given to non-invertible symmetries in dimensions higher than 3. These are characterized by the fact that the associated topological defects obey more general, not group-like fusions. In this talk I will present a prescription for constructing non-invertible symmetries by gauging outer-automorphism 0-form symmetries and apply it to some concrete gauge theory examples.

• Gerben Venken,  University of Heidelberg.

• Title: Curvature corrections to KPV: Do antibrane uplifts need deep throats?

• Abstract:  I discuss alpha'^2 curvature corrections to the action of the

NS5-brane which is central to the metastability analysis of warped

anti-D3-brane uplifts by Kachru, Pearson and Verlinde (KPV). These

corrections can dramatically alter the KPV analysis. For the

alpha'^2-corrections to be sufficiently small to recover essentially

the leading-order KPV potential one needs a surprisingly large radius

at the tip of the throat, corresponding to g_s M > 20. In the context

of the Large Volume Scenario (LVS) this implies a D3-tadpole of at

least O(10^3-10^4). However, large alpha'^2-corrections do not

necessarily spoil the uplift in KPV. Rather, as the curvature

corrections lower the tension of the brane, a novel uplifting

mechanism suggests itself where the smallness of the uplift is

achieved by a tuning of curvature corrections. A key underlying

assumption is the existence of a dense discretuum of g_s. This new

mechanism does not require a deep warped throat, thereby sidestepping

the main difficulty in uplifting KKLT and LVS. However, all of the

above has to be treated as a preliminary exploration of possibilities

since, at the moment, not all relevant corrections at the order

alpha'^2 are known.

• Joseph McGovern, University of Oxford

• Title: New examples of modular supersymmetric flux vacua

• Abstract: We compute the zeta function for a number of multiparameter Calabi-Yau threefolds. This is a generating function for point counts of these manifolds over finite fields. When the complex structure moduli space of these manifolds possesses a suitable $\mathbb{Z}_{2}$ symmetry, we find supersymmetric flux vacua on the fixed loci of this involution. In accordance with the Flux Modularity Conjecture of Kachru, Nally, and Yang (KNY) we observe that for these supersymmetric flux vacua the zeta function exhibits modular behaviour, so that one can read off weight-two modular newforms. In the F-theory uplift these newforms are associated to the F-theory curve by the modularity theorem, again in agreement with KNY. By applying Deligne's conjecture, we can evaluate derivatives of the Calabi-Yau periods in terms of L-values related to those elliptic curves.

• Jeroen Monnee, Utrecht U.

• Title: Bulk Reconstruction in Moduli Space Holography

• Abstract:  In recent years, asymptotic Hodge theory has been an essential tool for understanding the properties of field spaces in string compactifications. One such property is the emergence of universal algebraic structures near every boundary in the moduli space, dubbed boundary data. A fascinating result of Cattani, Kaplan and Schmid shows that using this simple data one can algorithmically recover the bulk of the moduli space (to a large extent). In this talk we discuss this procedure in detail and show that it can be applied in concrete examples to compute the period mapping of all one-modulus Calabi-Yau threefolds near any boundary.

• Juven Wang, Harvard U.

• Title: Cobordism and Deformation Class of the Standard Model and Beyond

• Abstract: 't Hooft anomalies of quantum field theories (QFTs) with an invertible global symmetry G (including spacetime and internal symmetries) in a d-dim spacetime are known to be classified by a d+1-dim cobordism group TPd+1(G), whose group generator is a d+1-dim cobordism invariant written as a d+1-dim invertible topological field theory. Deformation class of QFT is recently proposed to be specified by its symmetry G and a d+1-dim invertible topological field theory. Seemingly different QFTs of the same deformation class can be deformed to each other via quantum phase transitions. We ask which deformation class controls the 4d ungauged or gauged (SU(3)×SU(2)×U(1))/Zq Standard Model (SM) for q=1,2,3,6 with a continuous or discrete (B−L) symmetry and with also a compatible discrete baryon plus lepton Z_{2Nf} B+L symmetry. (The Z_{2Nf} B+L is discrete due to the ABJ anomaly under the BPST instanton.) We explore a systematic classification of candidate perturbative local and nonperturbative global anomalies of the 4d SM, including all these gauge and gravitational backgrounds, via a cobordism theory, which controls the SM's deformation class. While many Grand Unified Theories violating the discrete B+L symmetry suffer from the proton decay, the SM and some versions of Ultra Unification (constrained by Z_{16} class global anomaly that replaces sterile neutrinos with new exotic gapped/gapless topological or conformal sectors) can have a stable proton. Dictated by a Z_2 class global mixed gauge-gravitational anomaly, there can be a gapless deconfined quantum critical region between Georgi-Glashow and Pati-Salam models -- the Standard Model and beyond occur as neighbor phases. We will also comment on a new mechanism to give the neutrino mass via topological field theories and topological defects. Work based on arXiv:2112.14765, arXiv:2204.08393, arXiv:2202.13498, arXiv:2106.16248, arXiv:2012.15860, and references therein.

Ethan Torres, University of Pennsylvania

• Title: Getting High on Gluing Orbifolds,

• Abstract: Quantum field theories (QFTs) engineered from M-theory on singular non-compact manifolds often enjoy a rich dictionary between physical data and geometric quantities. For instance, when real codimension-4 ADE orbifold singularities extend out to the asymptotic boundary, the local operators of the QFT form representations of the flavor group whose Lie algebra is specified by the ADE-types. We present a novel geometric procedure to calculate the global structure of this flavor group. Additionally, taking into account line operators of the QFT, this structure may generalize to a 2-group and we give a geometric picture for this as well. I will showcase this procedure in some examples of 5d SCFTs engineered from M-theory on quotients of C^3. Based on work with M. Cvetic, J.J. Heckman, and M. Hubner (2203.10102)

Mudasar Sabir, Hua-Zhong U. Sci.

• Title: The Supersymmetry Breaking Soft Terms, and Fermion Masses and Mixings in the Supersymmetric Pati-Salam Model from Intersecting D6-branes

• Abstract: A supersymmetric Pati-Salam model with wrapping number equal to 5 has been constructed in Type IIA orientifolds on T6/(ℤ2×ℤ2) with intersecting D6-branes recently. In particular, the string-scale gauge coupling unification can be achieved due to the intermediate-scale vector-like particles from N=2 sector. We calculate the supersymmetry breaking soft terms, and study the Standard Model (SM) fermion masses and mixings. There are nine pairs of Higgs doublets from N=2 sector. Interestingly, we can explain the SM quark masses and mixings, as well as the charged leptons masses from three point and four-point Yukawa interactions. Moreover, we calculate the supersymmetry breaking soft terms in a previous model with gauge coupling unification since we find a typo in the previous study.

Alessia Platania, Perimeter

• Title: Asymptotic Safety and the Swampland,

• Abstract: We investigate the consequences of combining swampland conjectures with the requirement of asymptotic safety. To this end, we explore the infrared regime of asymptotically safe gravity in the quadratic one-loop approximation, and we identify the hypersurface spanned by the endpoints of asymptotically safe renormalization group trajectories. These comprise the allowed values of higher-derivative couplings as well as standard logarithmic form factors. We determine the intersection of this hypersurface with the regions of parameter space allowed by the weak-gravity conjecture, the swampland de Sitter conjecture, and the trans-Planckian censorship conjecture. The latter two depend on some order-one constants, for generic values of which we show that the overlap region is a proper subspace of the asymptotically safe hypersurface. Moreover, the latter lies inside the region allowed by the weak gravity conjecture assuming electromagnetic duality. Our results suggest a non-trivial interplay between the consistency conditions stemming from ultraviolet completeness of the renormalization group flow, black hole physics, and cosmology.

David Prieto, IFT

• Title: Membranes in AdS4 orientifold vacua and their Weak Gravity Conjecture,

• Abstract: We study type IIA orientifold compactifications with fluxes that give rise to perturbatively stable, non-supersymmetric AdS4 vacua with D6-brane gauge sectors. Non-perturbative instabilities can be mediated by D8-branes wrapped on the six internal dimensions X6, if they reduce to 4d membranes with a charge Q larger than its tension T. The mismatch between Q and T arises due to i) curvature corrections and ii) the BIon backreaction of D6-branes wrapping 3-cycles of X6. We give a simple expression for the second effect in toroidal orientifolds, and find that only pairs of 3-cycles at SU(2) angles contribute to it. They either contribute towards  Q>T or Q<T depending on the 3-cycles separation, allowing to engineer 4d N=0 vacua in tension with the Weak Gravity Conjecture for membranes. 

Gregory J. Loges, University of Wisconsin-Madison

• Title: Making Wormholes Stable Again,

• Abstract: Giddings-Strominger wormholes have had a long history as smooth solutions of axion-gravity, but their interpretation and role in the Euclidean path integral has been unclear. I will discuss the perturbative stability of these axion wormholes using the dual, 3-form description where many of the difficulties faced in the axion frame are absent. Based on [2203.01956] with Gary Shiu and Nidhi Sudhir.

Max Wiesner, Harvard & CMSA

• Title: Holography and the KKLT scenario,

• Abstract: The KKLT scenario, one of the few ideas to realize dS vacua in string theory, consists of two steps: the first involves the construction of a supersymmetric AdS vacuum with a small negative cosmological constant, whereas the second involves breaking supersymmetry and uplifting the energy to achieve dS. In this talk I use conventional holography to argue why it is not possible to complete the first step, i.e. to obtain supersymmetric AdS vacua with small cosmological constant in type IIB/F-theory flux compactifications. Holography identifies the radius of the AdS flux vacuum with the IR central charge of the worldvolume theory on 5-branes wrapping special Lagrangian cycles in CY fourfolds dual to the flux. I will show that, as a consequence of tadpole cancellation, the central charge of this worldvolume theory is bounded by the Euler characteristic of the fourfold. Since the species scale is also set by the Euler characteristic of the fourfold, the AdS scale is at best of the order of the species scale such that one can only obtain highly curved AdS vacua beyond the validity of the EFT.

Álvaro Herráez, IPhT

• Title: The Tadpole Conjecture in the Strict Asymptotic Limits,

• Abstract: The Tadpole Conjecture puts severe constraints on the stabilization of a large number of moduli by claiming that in such settings the flux contribution to the tadpole grows at least linearly with the number of stabilized fields. In this talk we study the complex structure sector of F-theory compactifications on Calabi-Yau four-folds. We present the first conceptual argument that explains this linear scaling of the tadpole and clarifies why it sets in only for a large number of stabilized moduli. This is done in the strict asymptotic limits of moduli space, by using the tools of asymptotic Hodge theory, which make possible an explicit discussion of moduli stabilization close to any boundary of moduli space and allow us to establish the relevant scaling constraints for the tadpole.

Niccolò Cribiori, Max Planck Inst.

• Title: Weak Gravity versus Scale Separation

• Abstract: The existence of a separation of scales between the four observed spacetime dimensions and the yet unobserved additional ones is a minimal requirement for (string) phenomenology. Explaining its origin at the theoretical level is an open problem. I will present a general argument excluding scale separation in supersymmetric anti-de Sitter vacua of four-dimensional N=2,8 supergravity as a consequence of the weak gravity conjecture. This suggests that N=0,1 supersymmetry at the lagrangian level could be the most promising chances to obtain a truly four-dimensional effective description of quantum gravity.

Anthony Ashmore, Chicago

• Title: Deformed N=1 SCFTs and their Supergravity Duals

• Abstract: We consider the space of supersymmetric AdS5 solutions of type IIB supergravity corresponding to the conformal manifold of the dual 4d N = 1 conformal field theories. We describe how the background geometry naturally encodes a generalised holomorphic structure, dual to the superpotential of the field theory. Using this perspective, we address the long-standing problem of finding the gravity dual of the generic N = 1 deformations of N = 4 super Yang-Mills: though we are not able to give it in a fully explicit form, we provide a proof-of-existence of the supergravity solutions. Using this formalism, we analyse the moduli of the supergravity backgrounds and derive a new result for the Hilbert series of the deformed field theories.

Bruno Bento, Liverpool

• Title: Gravity at the Tip of the Throat

• Abstract: Warped throats have been used in countless works in the context of string theory compactifications, in particular for their ability to suppress high energy scales. The Klebanov-Strassler solution gives us an explicit description of the geometry of a warped throat which we can use to perform computations - my focus will be on the gravitational sector of the resulting 4d EFT, with its tower of Kaluza-Klein (KK) gravitons. By assuming that we live on a (3+1)-dimensional brane somewhere along the throat, we can study how the warping influences the effects of the tower on the brane.
  In particular, I will show how the tower corrects the Newtonian potential and discuss how gravitational experiments and observations may be used to test the possibility that our Universe corresponds to a brane living in a warped throat. 

Andres Rios Tascon, Cornell

• Title: Computational Mirror Symmetry

• Abstract: Abstract: In this talk, I will show that compactifications of the Heterotic String on a circle exhibit at the boundary of moduli space (R->0, or equivalently the decompactification limit R->infinity) a tower of winding or momentum modes that enhance the
  E_8 x E_8 or SO(32) gauge algebras to the affine algebras (E_9​+ E_9)/~ (the identification means that the two copies of E9 share the same central extension) and \hat{D}_16, respectively. I will also argue that these towers of modes satisfy the Lattice Weak Gravity and Repulsive Force Conjectures.

Tom Rudelius, Berkeley 

• Title: Higher-Group Symmetries, Axion Strings, and Weak Gravity Conjecture Mixing

• Abstract:  I will present some results on the infinite-distance properties of families of unstable flux vacua in string theory with broken supersymmetry. In the absence of a conformal manifold, I will employ the more general quantum information metric on theory space. The relevant trajectory undertaken along the tunneling cascade is described by a holographic renormalization group flow. In one limit an exponentially light tower of Kaluza-Klein states appears, while in the opposite limit a tower of higher-spin excitations of D1-branes becomes light, realizing the emergent string proposal. Moreover, the anomalous dimensions of scalar vertex operators and single-trace higher-spin currents decay exponentially in the distance. The holographic description of the latter includes a free sector, whose emergent superconformal symmetry resonates with supersymmetric stability, the CFT distance conjecture and S-duality.

Veronica Collazuol, IPHT

• Title: E9 symmetry in the Heterotic Theory on S1 and the Weak Gravity Conjecture​

• Abstract: In this talk, I will show that compactifications of the Heterotic String on a circle exhibit at the boundary of moduli space (R->0, or equivalently the decompactification limit R->infinity) a tower of winding or momentum modes that enhance the
  E_8 x E_8 or SO(32) gauge algebras to the affine algebras (E_9​+ E_9)/~ (the identification means that the two copies of E9 share the same central extension) and \hat{D}_16, respectively. I will also argue that these towers of modes satisfy the Lattice Weak Gravity and Repulsive Force Conjectures.

Ivano Basile, Mons

• Title: Emergent strings at infinite distance with broken supersymmetry

• Abstract:  I will present some results on the infinite-distance properties of families of unstable flux vacua in string theory with broken supersymmetry. In the absence of a conformal manifold, I will employ the more general quantum information metric on theory space. The relevant trajectory undertaken along the tunneling cascade is described by a holographic renormalization group flow. In one limit an exponentially light tower of Kaluza-Klein states appears, while in the opposite limit a tower of higher-spin excitations of D1-branes becomes light, realizing the emergent string proposal. Moreover, the anomalous dimensions of scalar vertex operators and single-trace higher-spin currents decay exponentially in the distance. The holographic description of the latter includes a free sector, whose emergent superconformal symmetry resonates with supersymmetric stability, the CFT distance conjecture and S-duality.

Manki Kim, MIT

• Title: D(-1)-instanton superpotential in string theory

• Abstract:  In this talk, I will discuss the non-perturbative superpotential generated by D(-1)-branes in type IIB compactifications on orientifolds of Calabi-Yau threefold hypersurfaces. As a first step towards understanding D(-1)-instanton superpotential, I will consider orientifold compactifications in which all the D7-brane stacks carry SO(8) gauge groups and show that in such models the D(-1)-instanton superpotential vanishes.

Atakan Firat, MIT

• Title: D-instanton superpotential in type II string theory on Calabi-Yau orientifolds

• Abstract: In this talk, I will explain how one can fix the normalization of the D-instanton contribution to the superpotential in type II string theory on Calabi-Yau orientifolds using string field theory and show such normalization is holomorphic function of the moduli.  Along the way I will sketch the proof for a folk theorem relating D-instantons to space-filling D-branes on Calabi-Yau's.

Pramod Shukla, ICTP Trieste

• Title: Insights of (Global) String Model Building: Presumptions, Expectations and Reality

• Abstract: The aim of this talk is to motivate the need for explicit global constructions on the way of string (inspired) model building. In this regard I will discuss several (sub-)leading contributions to the type IIB effective scalar potentials induced from various sources, and the subsequent underlying assumptions one usually makes in order to engineer attractive models of e.g. moduli stabilization or inflation. Taking a phenomenologist friendly approach, I will discuss the feasibility and challenges of fulfilling those naive and apparently simple assumptions in "some models" while aiming to find concrete Calabi Yau orientifolds. For illustration purposes, using the Kreuzer-Skarke CY dataset as well as the projective Complete Intersection Calabi Yau (pCICY) dataset, I will also present the scanning results for "suitable" divisor topologies of the CY threefolds, and their relevance for moduli stabilization, say in particular for scanning/classifying the perturbatively flat vacua, and inflation.

Alessandra Gnecchi, MPI Munich

• Title: Large and Small Non-extremal Black Holes, Thermodynamics Dualities and the Swampland

• Abstract: I will consider charged black holes at finite temperature and investigate infinite distance limits of these configurations in the temperature (T) vs entropy (S) parameter space. Due to the coupling of the geometry to scalar fields, I will show how the large/small T limit, as well as the small/large S limit, are often associated to the appearance of a tower of massless states, pushing these solutions outside of the quantum gravity landscape and into the swampland. I will discuss how this can be associated to a temperature distance conjecture. I will consider general couplings of charged, dilatonic black holes, and show that the same considerations apply to multi-charge solutions of N=2 supergravity.

Alberto Castellano, IFT Madrid

• Title: IR/UV Mixing and The Swampland

• Abstract: By applying the  Bousso Bound to an EFT in a  box one  obtains that the UV and IR cut-offs of the EFT are necessarily correlated. We argue that in a theory of Quantum Gravity one should identify the UV cutoff with the `species scale', and give a general algorithm to calculate it in the case of multiple towers becoming light. One then obtains  an upper bound on the characteristic mass scale of the tower in terms of  the IR cut-off. Identifying such IR cut-off with a (non-vanishing) curvature in AdS one reproduces the statement of the AdS Distance Conjecture, also giving an explicit lower bound for the its relevant exponent. The UV/IR constraints found  apply to  both AdS and dS vacua.  We comment on possible applications of these ideas to the dS Swampland conjecture as well as to the observed dS phase of the universe.

David Cyncynates, Stanford

• Title: Friendship in the Axiverse

• Abstract: The Axiverse is a scenario in which axion-like particles are distributed over many orders of magnitude in mass and interact with one another through a joint potential. In this talk, I will show how non-linearities in this potential lead to a new type of resonant energy transfer between "friendly" axions with nearby masses. This resonance generically transfers energy from axions with larger decay constants to those with smaller decay constants, leading to a multitude of signatures. These include enhanced direct detection prospects for a resonant pair comprising even a small subcomponent of dark matter, and boosted small-scale structure if the pair is the majority of DM. Near-future iterations of experiments such as ADMX and DM Radio will be sensitive to this scenario, as will astrophysical probes of DM substructure.

• Gerben Venken, Heidelberg

• Title: The LVS Parametric Tadpole Constraint

• Abstract: The large volume scenario (LVS) for de Sitter compactifications of the type IIB string is in principle protected from various unknown corrections as the Calabi-Yau volume is exponentially large. However, as recently emphasised, the most explicit models are in practice on the border of parametric control. In this talk I identify what we believe to be the main issue behind this difficulty: A large volume implies a shallow AdS minimum and hence a small uplift. The latter, if it relies on an anti-D3 in a throat, requires a large negative tadpole. I provide a simple and explicit constraint for what this tadpole has to be in order to control the most dangerous corrections. The fundamental ingredients are parameters specifying the desired quality of control. I discuss directions for future work which could lead to LVS constructions satisfying our constraint with better control and the interplay between our constraint and the tadpole conjecture. Our constraint then represents a very concrete challenge for future searches for and the understanding of relevant geometries. Based on 2202.04087 .

Alberto Castellano, IFT Madrid

• Title: IR/UV Mixing and The Swampland

• Abstract: By applying the  Bousso Bound to an EFT in a  box one  obtains that the UV and IR cut-offs of the EFT are necessarily correlated. We argue that in a theory of Quantum Gravity one should identify the UV cutoff with the `species scale', and give a general algorithm to calculate it in the case of multiple towers becoming light. One then obtains  an upper bound on the characteristic mass scale of the tower in terms of  the IR cut-off. Identifying such IR cut-off with a (non-vanishing) curvature in AdS one reproduces the statement of the AdS Distance Conjecture, also giving an explicit lower bound for the its relevant exponent. The UV/IR constraints found  apply to  both AdS and dS vacua.  We comment on possible applications of these ideas to the dS Swampland conjecture as well as to the observed dS phase of the universe.

David Cyncynates, Stanford

• Title: Friendship in the Axiverse

• Abstract: The Axiverse is a scenario in which axion-like particles are distributed over many orders of magnitude in mass and interact with one another through a joint potential. In this talk, I will show how non-linearities in this potential lead to a new type of resonant energy transfer between "friendly" axions with nearby masses. This resonance generically transfers energy from axions with larger decay constants to those with smaller decay constants, leading to a multitude of signatures. These include enhanced direct detection prospects for a resonant pair comprising even a small subcomponent of dark matter, and boosted small-scale structure if the pair is the majority of DM. Near-future iterations of experiments such as ADMX and DM Radio will be sensitive to this scenario, as will astrophysical probes of DM substructure.

Irene Valenzuela, UAM

• Title: The Desert and the Swampland

• Abstract: The most natural expectation away from asymptotic limits in moduli space of supergravity theories is the desert scenario, where there are few states between massless fields and the quantum gravity cutoff. We initiate a systematic study of these regions deep in the moduli space, and compute the maximum value of the cutoff given by BPS states in large classes of supersymmetric vacua. We show that even though heuristically the species scale is compatible with expectations, the BPS states of the actual string vacua lead to a stronger dependence of the cutoff scale on the number of massless modes. We propose that this discrepancy can be resolved by placing a bound on the number of massless modes that is consistent with quantum gravity.

Luigi Tizzano, ULB

• Title: Anomaly Matching Across Dimensions and Supersymmetric Cardy Formulae

• Abstract: 't Hooft anomalies are known to induce specific contributions to the effective action at finite temperature. We present a general method to directly calculate such contributions from the anomaly polynomial of a given theory, including a term which involves a U(1) connection for the thermal circle isometry. Based on this observation, we show that the asymptotic behavior of the superconformal index of 4d N=1 theories can be calculated by integrating the anomaly polynomial on a particular background. Finally, we discuss how such asymptotic behavior captures the Bekenstein-Hawking entropy and phases of supersymmetric black holes in AdS. 

Federico Carta, Durham

• Title: Small flux superpotential and divisor topologies

• Abstract: In this talk we discuss aspects of complex structure moduli stabilization in type IIB Calabi-Yau orientifolds. We will start reviewing the importance of obtaining an exponentially small flux superpotential W_0 in the context of KKLT, and a nice algorithm by the Cornell group which allows to obtain such result. We then proceed to study Calabi-Yaus in the Kreuzer-Skarke database, as well as the mirrors of the pCICYs (up to h11=2). Among them, we systematically identify which ones can be used to engineer models with small flux superpotentials, and list the resulting vacua. We briefly comment about the existence of vacua which remain flat even after the leading Gopakumar-Vafa corrections are included. Finally, we discuss the topology of divisors of pCICYs, and remark on their relevance for global model building.

Flavio Tonioni, Liverpool

• Title: Misaligned Supersymmetry in String Theory

• Abstract: Misaligned supersymmetry characterises a variety of non-supersymmetric string models: even if the particle spectrum lacks a one-by-one matching between fermionic and bosonic degrees of freedom, there exist theories in which an infinite oscillation between fermionic and bosonic surpluses results in cancellations leading to a finite one-loop cosmological constant. Misaligned supersymmetry has been often discussed with regard to closed-string theories and at leading order in the expansion of the net state degeneracies. After a general overview, for both open and closed strings, I will describe how to extend this beyond leading order and elucidate the mathematics underlying the heuristic interpretation of misaligned supersymmetry as a key to the one-loop cosmological constant finiteness. This can help in shedding further light on the relationship between supersymmetry and string theory.

Craig Lawrie, DESY

• Title: Infinitely-many 4d SCFTs with a=c

• Abstract: I will explore a special subset of the 4d SCFT landscape, with N=1 and N=2 supersymmetry and identical central charges: a = c, without any large N limit. Such SCFTs are obtained via N=1 or N=2 diagonal gauging of collections of non-Lagrangian Argyres--Douglas and conformal matter theories and I will discuss the classification problem for consistent gaugings with interacting infrared SCFTs in both cases. For N=2, the classification is in terms of an ADE Dynkin diagram Γ. Moreover, we find that the Schur indices for such theories can be written in terms of that of N=4 super-Yang-Mills theory upon rescaling fugacities. For generic choices of Γ and G, it can be regarded as a generalization of the affine quiver gauge theory obtained from D3-branes probing singularity of type Γ. For N=1, there exists a vast collection of gaugings, including with additional chiral multiplets on the gauge node, that flow in the infrared to interacting SCFTs with a=c, and I highlight some of their features.

Kajal Singh, HCRI 

• Title: Exploring Aspects of the String Landscape

• Abstract: In type IIB flux compactifications, the magnitude of the vev of the Gukov-Vafa-Witten superpotential W_0 plays an important role. Recently exponentially small values of W_0 were achieved by constructing perturbatively flat vacua. In this talk, we will explore these vacua in a statistical context. I will discuss our findings using the 2-moduli case as an example and will generalize it to higher moduli. I will also present a statistical study of low energy physics after taking Kähler moduli stabilization into consideration, which is crucial to get reliable vacua.

Enrico Pajer, Cambridge

• Title: From locality and unitarity to cosmological correlators

• Abstract: In this talk, I will report on recent progress in developing a new "bootstrap" approach to perturbative QFT in de Sitter. The bootstrap approach builds directly upon the fundamental pillars of physics. In particular, I will discuss the recent breakthroughs in understanding the consequence of unitarity for cosmological correlators to all orders in perturbation theory, as well as the footprint of (bulk) locality. These principles can be used to derive many classical and new inflationary predictions associated with primordial non-Gaussianity in a way that is both computationally simpler and conceptually more transparent. Extending these results beyond perturbation theory might give us a tool to exclude theories without a consistent UV completion in de Sitter, and a useful framework to develop de Sitter holography.

Andreas Schachner, Cambridge 

• Title: The Large Scale Structure of α' Effects in String Theory

• Abstract: In this talk, I discuss three approaches to understanding and completing the 10-dimensional effective actions of type II superstring theory. I provide concrete evidence at the level of 5-point superstring amplitudes that higher derivative terms in the maximally U(1)-violating (MUV) sector are obtained from standard superspace integrals over sixteen fermionic coordinates. This is in agreement with 11D superparticle amplitudes in M-theory where modular forms required for SL(2,Z) invariance of type IIB arise explicitly from integrating out winding modes on a 2-torus. Lastly, I argue that these observations can be generalised to the complete MUV sector of the type IIB effective action for the complex 3-form and the metric.

Lars Aalsma, Madison

• Title: Extremal Black Hole Corrections from Iyer-Wald

• Abstract: Extremal black holes play a key role in our understanding of various swampland conjectures and in particular the WGC. The mild form of the WGC states that higher-derivative corrections should decrease the mass of extremal black holes at fixed charge. Whether or not this conjecture is satisfied depends on the sign of the combination of Wilson coefficients that control corrections to extremality. Typically, corrections to extremality need to be computed on a case-by-case basis, but in this talk I will present a universal derivation of extremal black hole corrections using the Iyer-Wald formalism. This leads to a formula that expresses general corrections to the extremality bound in terms of the stress tensor of the perturbations under consideration, clarifying the relation between the WGC and energy conditions. This shows that a necessary condition for the mild form of the WGC to be satisfied is a violation of the Dominant Energy Condition. This talk is based on 2111.04201.

Nava Gaddam, Utrecht

• Title: Page curve and emergent soft theorems from black hole scattering

• Abstract: I hope to convey the following three messages in this talk:

1. There is a new interesting phase of quantum gravity where black hole scattering matrix elements can be computed in effective field theory.

2. These scattering amplitudes reveal the dynamics leading to information retrieval after Page time.

3. Remarkably, new emergent soft-graviton theorems arise near the black hole horizon in this phase.

Max Wiesner, Harvard

• Title: Light Strings and Strong Coupling

• Abstract: In this talk I will discuss a relation between light perturbative strings and strong coupling singularities in the Kähler moduli space of 4d N=1 compactifications of F-theory. In limits of the Kähler moduli space where a critical string becomes light, the F-theory moduli space reduces to the stringy moduli space of this light string. In certain cases, this allows to extract the non-perturbative singularity structure of the local F-theory moduli space. I will show that for simple setups with a heterotic dual description, a strong coupling singularity for a D7-brane gauge theory occurs in the region of moduli space where the critical string is classically expected to be light. In the vicinity of this non-perturbative singularity, the string can be shown to leave the spectrum of light strings thereby providing a non-perturbative explanation for the censoring of certain classical weak coupling limits in F-theory which were previously argued for at the purely perturbative level. On the other hand for the weakly-coupled critical string to remain part of the light string spectrum, the moduli space needs to factorise in a certain way. The strong coupling singularity occur whenever this factorisation is not protected by the string and broken at the quantum level.

Jakob Moritz, Cornell

• Title: Modular Superpotentials from Singular Divisors

• Abstract: We study Euclidean D3-branes wrapping holomorphic divisors D with normal crossing singularities along rational curves, in compactifications of type IIB string theory on orientifolds of Calabi-Yau threefolds.  Witten's counting of fermion zero modes on smooth divisors D in terms of the cohomology of the structure sheaf O_D is not directly applicable in this setting. We argue that fermion zero modes are instead captured by the line bundle cohomology of the log resolution of D. We show this by detailing compactifications in which the normal crossing singularities can be unwound by passing through suitable flop transitions, giving a physical incarnation of the log resolution process. Analytically continuing the superpotential through the flops, we find non-vanishing results even in geometric phases where normal crossing singularities are present. Furthermore, these compactifications feature infinitely many isomorphic geometric phases, and thus give rise to infinite order monodromy groups Gamma, whose action on effective divisors can be used to determine exact effective cones, with infinitely many generators related to each other by the action of Gamma.  As a consequence, the non-perturbative superpotentials can be resummed into Jacobi theta functions, whose modular symmetries suggest the existence of strong/weak coupling dualities involving inversion of divisor volumes.

Junsei Tokuda, Kobe

• Title: Swampland conditions on scalar potentials from positivity bounds

• Abstract: Various swampland conditions have been conjectured with various rigors and motivations. It is interesting if these swampland conjectures can be derived. We study positivity bounds on scalar field theories coupled to gravity under several clear assumptions on scattering amplitudes. We find that positivity bounds imply that scalar potentials cannot be arbitrarily flat unless some new physics enters well below the Planck scale. Our result provides a swampland condition for scalar potentials.

Paul Oehlmann, Uppsala

• Title: Gauged 2-form symmetries in 6D SUGRAs

• Abstract: 6D N=(2,0) and (1,0) SCFTs admit a wide range of global symmetries that are expected to be either broken or gauged when coupled to gravity. One particular symmetry is that of a discrete self-dual 2 form symmetry that couples the tensionless BPS strings to Wilson surface operators. Such SUGRA theories can be geometrically engineered in IIB and F-theory. We show that global symmetries are generically absent and derive a geometric condition on the BPS string embedding into the compact geometry such that a gauged 2-form symmetry survives. We check our proposal via various dualities, where the 2-form symmetry reduces to a 1-form symmetry in 5D.

Nicole Righi, DESY

• Title:  Fuzzy Dark Matter Candidates from String Theory

• Abstract:  We provide a string theoretical explanation of fuzzy dark matter as composed by ultralight axions coming from the compactification of type IIB string theory on Calabi-yau manifolds. In particular, we consider C2 and C4 axions stabilased in a Large Volume Scenario, and thraxions, axionic modes living in warped throats of the internal manifold. Based on the latest bounds, we study how likely it is for dark matter to be composed of such particles and in which abundance. We provide predictions on the preferred ranges of masses and decay constants when string axions behave as FDM. Moreover, requiring those axions to lie in the FDM range imposes constraints on the features of the internal manifold. We also comment on implications for the Weak Gravity Conjecture.

Joe Conlon, Oxford

• Title:  Exploring the Holographic Swampland

• Abstract:  I describe our work looking at `traditional' scenarios of moduli stabilisation from a holographic perspective. This reveals some interesting structure that is not apparent from the top-down perspective. For vacua in the extreme regions of moduli space, such as LVS in type IIB or the DGKT flux vacua in type IIA, the dual moduli conformal dimensions reduce to fixed values - in a certain sense, the low-conformal dimension part of the CFT is unique and independent of the large number of flux choices. For the DGKT flux vacua these conformal dimensions are also integer, for reasons we do not understand.

Gregory Loges, Madison

• Title: Breeding Branes

• Abstract:  Machine learning has proven to be a useful tool in understanding the landscape of string vacua. One rich corner to explore is that of intersecting D6-branes on toroidal orbifolds, where the consistency conditions are simply phrased in terms of integer winding numbers. I will discuss ongoing work using genetic algorithms to search for consistent, MSSM-like models in this setting.

John Stout, Harvard

• Title: Axion Masses from Monopoles

• Abstract: I will describe a novel contribution to an axion's effective potential: loops of virtual magnetic monopoles. Gauge kinematics demand that monopoles must acquire an electric charge in the presence of a theta angle. Since the electric field sourced by this induced charge forces the monopole mass to depend on the theta angle, integrating out these states will generate a theta-dependent contribution to the vacuum energy, i.e. an axion effective potential, even in a gauge theories with no instantons.

Damian van de Heisteeg, Utrecht

• Title: Title: Moduli Stabilization in Asymptotic String Compactifications

• Abstract: In this talk we discuss novel approaches to moduli stabilization in Type IIB flux compactifications. Our strategies rely on recent insights about Calabi-Yau moduli spaces based on asymptotic Hodge theory. In the first approach we engineer flux vacua with small superpotentials by using certain essential exponential corrections. In the second approach we set up a systematic three-step approximation scheme by using asymptotic sl(2)-structures.

Mateo Galdeano, Oxford

• Title: Superconformal Algebras for (Generalized) Connected Sums

• Abstract: When string theory is compactified on special holonomy manifolds, a fascinating correspondence arises: covariantly constant forms are associated to currents in the worldsheet chiral algebra. I will discuss this relation in the context of Generalized Connected Sum Spin(7) manifolds, which are constructed by gluing together two open manifolds along isomorphic asymptotic ends. The geometric structure is reproduced in the worldsheet algebra, and this can be exploited to shed some light on Spin(7) mirror symmetry. This talk is based on joint work with M.-A. Fiset, [2104.05716].

Matilda Delgado, IFT Madrid

• Title: Dynamical Cobordism and Swampland Distance Conjectures

• Abstract: We consider spacetime-dependent solutions to string theory models with tadpoles for dynamical fields, arising from non-trivial scalar potentials. The solutions have necessarily finite extent in spacetime, and are capped off by boundaries at a finite distance, in a dynamical realization of the Cobordism Conjecture. We show that as the configuration approaches these cobordism walls of nothing, the scalar fields run off to infinite distance in moduli space, allowing one to explore the implications of the Swampland Distance Conjecture. We uncover new interesting scaling relations linking the moduli space distance and the SDC tower scale to spacetime geometric quantities, such as the distance to the wall and the scalar curvature. We show that walls at which scalars remain at finite distance in moduli space correspond to domain walls separating different (but cobordant) theories/vacua; this still applies even if the scalars reach finite distance singularities in moduli space, such as conifold points. We illustrate our ideas with explicit examples in massive IIA theory and M-theory on CY threefolds. In 4d N=1 theories, our framework reproduces a recent proposal to explore the SDC using 4d string-like solutions.

Xingyang Yu, NYU

• Title: 2d N=(0,1) gauge theories, Spin(7) orientifolds and triality

• Abstract: I will introduce a new brane engineering for 2d minimally supersymmetric, i.e. N=(0,1), gauge theories. Starting with 2d N=(0,2) gauge theories on D1-branes probing Calabi-Yau 4-folds, a brand new orientifold configuration named ’Spin(7) orientifold’ is constructed and the resultant 2d N=(0,1) theories on D1-branes are derived. Using this method, one can build an infinite family of 2d N=(0,1) gauge theories explicitly. Furthermore, the N=(0,1) triality, proposed by Gukov, Pei and Putrov, enjoys a geometric interpretation as the non-uniqueness of the map between gauge theories and Spin(7) orientifolds. The (0,1) triality can then be regarded as inherited from the N=(0,2) triality of gauge theories associated with Calabi-Yau 4-folds.

• Title: BIonic membranes and AdS instabilities

• Abstract: We study 4d membranes in type IIA flux compactifications of the form AdS4 x X_6, where X_6 admits a Calabi--Yau metric. These models feature scale separation and D6-branes/O6-planes on three-cycles of X_6. When the latter are treated as localised sources, explicit solutions to the 10d equations of motion and Bianchi identities are known in 4d N=1 settings, valid at first order in an expansion parameter related to the AdS4 cosmological constant. We extend such solutions to a family of perturbatively stable N=0 vacua, and analyse their non-perturbative stability by looking at 4d membranes. We find that either D4-branes or anti-D4-branes on holomorphic curves feel no force in both N =1 and N=0 AdS4. Differently, D8-branes wrapping X_6 and with D6-branes ending on them can be attracted towards the boundary of N=0 AdS4. The source of imbalance is the curvature of X_6 and the D8/D6-system BIon profile. The latter dominates when X_6 is a (blown-up) toroidal orbifold, rendering such 4d membranes superextremal. We argue that N=0 vacua of this sort with space-time filling D6-branes are unstable against bubble nucleation, and decay to N=0 vacua with less D6-branes and larger Romans mass.

Robert Rosati, UT Austin

• Title: Rapid-turn inflation in supergravity is rare and tachyonic

• Abstract: Strongly non-geodesic, or rapidly turning, trajectories in multifield inflation have attracted much interest recently from both theoretical and phenomenological perspectives. For example, such trajectories can evade the eta-problem in fat inflation, in which all inflatons are heavier than the Hubble scale. Most models with large turning rates in the literature are formulated as effective field theories. In this talk I'll discuss some investigations into rapid-turn inflation in supergravity as a first step toward understanding them in string theory. We find that large turning rates can be generated in a wide class of models, at the cost of high field space curvature. However, in these models one field is always tachyonic along the inflationary trajectory, implying that fat inflation may not be viable in supergravity. The high curvatures underscore the difficulty of obtaining rapid-turn inflation in realistic string-theoretical models.

Saghar Sophie Hosseini, Durham

• Title: Higher form symmetries of geometrically engineered field theories

• Abstract: I will discuss the geometric origin of higher form symmetries of quantum field theories. These symmetries may be found systematically in terms of the defect groups from geometric engineering in string theories, M-theory and F-theory. The flux non-commutativity in string theory constrains the corresponding global structures of the associated quantum fields.

Pietro Ferrero, Oxford

• Title: Gluon scattering in AdS from CFT

• Abstract: I will present a class of recently computed holographic correlators between half-BPS operators in a vast array of SCFTs with non-maximal superconformal symmetry in dimensions d=3,4,5,6. Via AdS/CFT, these four-point functions are dual to gluon scattering amplitudes in AdS. I will show that, at tree level, all such correlators are completely fixed by symmetries and consistency conditions. Our results encode a wealth of CFT data and exhibit various emergent structures, including Parisi-Sourlas supersymmetry, hidden conformal symmetry and color-kinematics duality.

Naomi Gendler, Cornell

• Title: PQ Axiverse

• Abstract: We show that the strong CP problem is solved in a large class of compactifications of string theory. The Peccei-Quinn mechanism solves the strong CP problem if the quality of the QCD axion is high, meaning that the breaking of the axion shift symmetry by the ultraviolet completion of gravity and of QCD is small compared to the CP-preserving axion potential generated by low-energy QCD instantons. We consider type IIB flux compactifications on Calabi-Yau hypersurfaces, taking a simple model of QCD on D7-branes. We compute an upper bound on the shift symmetry breaking from D-brane instanton couplings to hidden-sector axions, and from high-energy instantons in QCD. We find that in theories with a sufficiently large number of axions, the instantons that could perturb the vev of the QCD axion away from zero typically have large actions, and thus do not spoil Peccei-Quinn quality. Furthermore, we find that for the majority of geometries in a certain range of h^{1,1}, the axion masses and decay constants are compatible with standard cosmological and astrophysical constraints.

Vincent Van Hemelryck, Leuven

• Title: Scale-separated AdS4 vacua of IIA orientifolds and M-theory

• Abstract: Obtaining string compactifications where the KK scale is much higher than the cosmological constant scale is quite challenging. Such a separation of scales is however necessary for the theory to be genuinely lower-dimensional. In massive type IIA string theory there are such scale-separated vacua, e.g. the DGKT AdS4 solutions. It has been shown recently that the classical orientifold backreaction in these vacua can be tuned small. In this talk I show that massless IIA on the other hand allows both weakly and strongly coupled AdS4 vacua that exhibit scale separation and for which the backreaction can be tuned small as well. I will give evidence that the strongly coupled solutions can be lifted to scale separated and sourceless (but classically singular) geometries in 11D supergravity.

Thomas Vandermeulen, SUNY Albany

• Title: A Constructive Approach to Orbifolds

• Abstract: I will discuss an approach to constructing orbifold partition functions that puts modular invariance at the forefront, preserving it even for e.g. asymmetric actions.  We will see how this approach always produces a consistent theory, which can be seen to decompose into a direct sum of orbifolds by non-anomalous subgroups of the orbifold group.  This construction relates to a general method of resolving anomalies by group extensions, which we will examine in the context of orbifolds.

Robin Schneider, Uppsala

• Title: Deep learning of Calabi-Yau metrics

• Abstract: In this talk I will present a new open source package for approximating Calabi-Yau metrics. The metric tensor can be modeled by different neural networks, which take the complex and Kähler moduli as user specified input. Experimental results are compared against previous studies on the Fermat Quintic from the literature. Furthermore, I demonstrate that the learned metric tensor on the Bicubic manifold obeys the slope equation for line bundles.

Marieke van Beest, Oxford

• Title: Holography, 1-Form Symmetries, and Confinement

• Abstract: I will discuss confinement in 4d N = 1 SU(N) Super-Yang Mills from a holographic point of view, focusing on the 1-form symmetry and its mixed 0-/1-form symmetry anomaly, which is closely related to chiral symmetry breaking. From the dual gravity description we also identify the IR 4d topological field theory, which realises chiral symmetry breaking and matches the mixed anomaly. The talk is based on [2104.12764].

Martin Bies, UPenn

• Title: Root Bundles and Towards Exact Matter Spectra of F-theory MSSMs

• Abstract: Root bundles recently entered the quest for F-theory MSSM as their cohomologies count the vector-like spectra, which includes the number of Higgs pairs. I will elaborate on these developments by present the work done in 2102.10115 and 2104.08297.

Ethan Torres, UPenn

• Title: On Reflection Anomalies and Matter Content of M-theory on Local Spin(7) Spaces

• Abstract: M-theory compactified on local Spin(7) spaces fibered by ALE singularities engineer 3d N=1 gauge theories coupled to matter which are often strongly coupled in the infrared. Despite the lack of holomorphic tools, some mileage can be gained when the field theory is symmetric under spatial reflections. One can measure a mod-16 't Hooft anomaly that captures the obstruction to placing the theory on a non-orientable manifold (i.e. a mixed reflection-gravity anomaly) and restricts the possible low energy phases. I will discuss some recent work on how to compute this anomaly for various compactification geometries built using Higgs bundle constructions. Along the way we will see how CPT-like symmetries descend from M-theory to 7d SYM to the 3d field theory, and find (perhaps surprisingly) that natural choices for how to define these symmetries in each setting are quite different from one another. (Based on work with M.Cvetic, J.Heckman, and G.Zoccarato. hep-th/2107.00025) 

Lorenz Schlechter, Utrecht

• Title: Generalized Clausen identities and the swampland distance conjecture

• Abstract: Clausen's hypergeometric identity relates the periods of certain K3 manifolds to the periods of elliptic curves. We show that generalizations of this identity together with period relations are sufficient to obtain global closed forms for the periods of all 1-parameter K3 manifolds valid in all phases. This mechanism can be further generalized to include all K3-manifolds as well as Fano 3-folds. The closed forms are used to compute distances in the moduli space of Calabi-Yau 3-folds analytically.

Sebastian Dumitru, UPenn

• Title: Line Bundle Hidden Sectors for Strongly Coupled Heterotic Standard Models

• Abstract: We present a formalism for constructing hidden-sector bundles induced from single line bundles, within the context of strongly coupled heterotic M-theory. We review the compactification from the eleven-dimensional Hořava-Witten orbifold to five-dimensional heterotic M-theory on a Schoen Calabi-Yau threefold, as well as the specific SU(4) vector bundle on the observable sector, which leads to the B−L MSSM low energy spectrum. In addition, we discuss a set of theoretical and phenomenological constraints and propose a viable vacuum configuration to satisfy them, which includes a specific hidden sector line bundle. For instance, one of the conditions that we demand is that N=1 supersymmetry is preserved at the compactification scale. This requirement allows us to attach a possible mechanism to break supersymmetry at low energy scales: gaugino condensation in the hidden sector. The condensation scale is computed and found to be low enough to be compatible with the energy scales available at the LHC.

First Talk

• Title: Bounce of Nothing

• Abstract: Theories with compact extra dimensions are sometimes unstable to decay into a bubble of nothing – an instability resulting in the destruction of spacetime. In this talk, I will discuss the existence of these bubbles in theories where the moduli fields that set the size of the extra dimensions are stabilized at a positive vacuum energy – a necessary ingredient of any theory that aspires to describe the real world. Using bottom-up methods, and focusing on a five-dimensional toy model, I will argue that four-dimensional de Sitter vacua admit bubbles of nothing for a wide class of stabilizing potentials. I will show that, unlike ordinary Coleman-De Luccia tunneling, the corresponding decay rate remains non-zero in the limit of vanishing vacuum energy. Potential implications include a lower bound on the size of compactified dimensions.

Second Talk

• Title: The FL bound and its phenomenological implications

• Abstract: The Festina Lente (FL) bound is a generalization of the Weak Gravity Conjecture to models of positive vacuum energy, which arises from demanding that extremal, large black holes must decay in a nonsingular way. It states that the mass of every charged state is lower-bounded by the vacuum energy scale. In this talk I will review the derivation of the bound, discuss some tentative evidence in string compactifications, and discuss a number of pheno implications ranging from neutrino and Higgs physics to antibrane uplifting scenarios.

First Talk

• Title: Cyclic Free Quotients of Favorable CICY-3 Folds

• Abstract: Free quotients of CICY-3 folds are important for string theory model building. In this talk we will report some progress on classifying all the cyclic free quotients of CICY-3 folds associated to their newly found favorable configurations presented in https://arxiv.org/abs/1708.07907. In the first part of the talk, I will discuss some basics of CICY free quotients. After this I will discuss a method introduced by Braun to judge fixed points freeness of a quotient manifold by using character valued indices of invariant line bundles. After this we will talk about the scanning process using the above method and finally we will discuss the new symmetries we obtained.

Second Talk

• Title: Yukawa textures from spectral data

• Abstract: Consider a Heterotic model (X,V) with X being an elliptically fibered Calabi-Yau threefold and V a stable holomorphic degree zero bundle. We compute the Yukawa textures of the effective theory in terms of the spectral data (i.e. the Fourier transform) of V. In addition, we will be able to find vanishing theorems in some cases. This approach has several advantages relative to the usual techniques: first, the Yukawa textures can be related to “simpler” cohomology groups, second, it can be easily related to the Higgs bundle spectral data over 7-branes, and the Yukawa textures of the local F-theory models. Since most of the Calabi-Yau threefolds are elliptically fibered this approach can be used in many cases.

First Talk

• Title: Constraints on SM from AdS conjectures

• Abstract: We consider constraints on D-dimensional EFTs in Minkowski, dS and AdS backgrounds in the light of AdS swampland conjectures as applied to their compactification in a circle. In particular we consider the non-SUSY AdS instability conjecture and the AdS distance conjecture. For Minkowski and dS vacua the results may be summarized by a Light Fermion Conjecture which states that if (-1)^(k+1) times the first non-vanishing supertrace is positive then a surplus of light fermions with masses smaller (or equal) than the cosmological constant must be present. We then focus on extensions of the SM with sterile neutrinos and find constraints on the mass of the lightest neutrino and rule out the standard See-Saw mechanism. Finally, we consider an extension of the SM including a quintessence field and show how the generalization of the dS conjecture to AdS vacua leads to similar results.

Second Talk

• Title: Z5 Symmetries in F-theory, Homological Projective Duality and Modular Forms

• Abstract: Genus-one fibered Calabi-Yau manifolds with 5-sections lead to F-theory vacua with Z_5 gauge symmetry. Geometrically, the N-section case with N>4 is interesting because the normal form of the fibers is not a complete intersection in a toric ambient space. This turns out to have striking implications for the modular structure of the topological string partition functions. One of the tools in our analysis are elliptic complete intersections in toric ambient spaces that lead to vacua with charge 5 matter in F-theory. Using Higgs transitions, which geometrically correspond to extremal transitions to genus-one fibrations with 5-sections, we discover a beautiful interplay between the modular structures on different genus-one fibrations, the associated physics in M-/F-theory and non-Abelian GLSMs, as well as the arithmetic and algebraic geometry.

First Talk

• Title: Modelling General asymptotic Calabi-Yau Periods

• Abstract: I will discuss an approach to the general study of period vectors of Calabi-Yau threefolds in asymptotic regions of complex structure moduli space. These period vectors play an important role in string compacitifcations, making a better understanding of their general structure desirable. The strategy is to exploit constraints imposed by completeness, symmetry, and positivity, which are formalised in asymptotic Hodge theory. Together with the classification of all possible boundaries in moduli space, these principles allow for a systematic construction of models for the asymptotic period vectors. One also gains insight about the necessity of exponentially suppressed corrections to the polynomial part of the period vector when away from the well-studied large complex structure point.

Second Talk

• Title: F-theory flux vacua at large complex structure

• Abstract: We compute the flux-induced F-term potential in 4d F-theory compactifications at large complex structure. In this regime, each complex structure field splits as an axionic field plus its saxionic partner, and the classical F-term potential takes the form V = Z^{AB}ρ_Aρ_B with ρ depending on the fluxes and axions and Z on the saxions. We provide explicit, general expressions for Z and ρ, and from there analyse the set of flux vacua, for an arbitrary number of fields. We identify two families of vacua with all complex structure fields fixed and a flux contribution to the tadpole Nflux which is bounded. In the first and most generic one, the saxion vevs are bounded from above by a power of Nflux. In the second, their vevs may be unbounded and Nflux is a product of two arbitrary integers, unlike what is claimed by the Tadpole Conjecture. We specialise to type IIB orientifolds, where both families of vacua are present, and link our analysis with several results in the literature. We finally illustrate our findings with several examples.

First Talk

• Title: Open string methods and Gopakumar-Vafa invariants

• Abstract: Topological invariants of singular Calabi-Yau threefolds, besides being of intrinsic interest for mathematicians, are objects that have great consequences in physics, as their properties are believed to capture instantonic effects in effective field theories arising from string compactifications. We are interested in finding new efficient ways of computing a specific class of topological invariants, known as Gopakumar-Vafa invariants, using string theory methods, thus also providing physical intuition about their origin. With this objective in mind, we focus on a class of non-toric Calabi-Yau threefolds in M-theory, exploiting the duality with type IIA to describe them in terms of D6-branes and O6-planes. In such setting, the tachyon condensation mechanism shows that computing Gopakumar-Vafa invariants is nothing but counting the states of strings stretching between the D6-branes. We show this technique in action for a variety of concrete examples, highlighting connections to the T-brane formalism and other physical implications.

Second Talk

• Title:8d Supergravity, Reconstruction of Internal Geometry and the Swampland

• Abstract: We sharpen Swampland constraints on 8d supergravity theories by studying consistency conditions on worldvolume theory of 3-brane probes. Combined with a stronger form of the cobordism conjecture, this leads to the reconstruction of the compact internal geometry and implies strong restrictions on the gauge algebra and on the level of the current algebra on the 1-brane probe. In particular, we argue that 8d supergravity theories with g2 gauge symmetry are in the Swampland. These results provide further evidence for the string lamppost principle in 8d with 16 supercharges.

First Talk

• Title: On string vacua without supersymmetry

• Abstract: We discuss the existence and stability of vacua in string theories where supersymmetry is either absent or broken at the string scale. In particular we present no-go results regarding de Sitter compactifications, connecting them to some Swampland conjectures, thereby focusing on anti-de Sitter (AdS) flux vacua arising from the USp(32) and U(32) orientifold models and from the SO(16) x SO(16) heterotic model. We investigate perturbative and non-perturbative instabilities and frame the vacua in terms of brane stacks, analyzing their back-reacted geometry and reproducing AdS in the near-horizon limit. Then we describe the instabilities in terms of brane interactions, connecting this scenario to some Swampland conjectures and to braneworld cosmology.

Second Talk

• Title:Holography, 1-Form Symmetries and Confinement

• Abstract: I will discuss confinement in 4d N = 1 SU(N) Super-Yang Mills (SYM) from holography, focusing on the 1-form symmetry and the holographic realization in terms of the Klebanov-Strassler solution. I will show how from the 5d consistent truncation it is possible to identify the topological couplings that determine the 1-form symmetry (and thus global forms of the gauge group) and its ’t Hooft anomalies. One of the topological couplings corresponds to a mixed 0-1-form symmetry anomaly, which is related to chiral symmetry breaking in the infrared (IR) vacuum. I will then discuss how other couplings in the 5d supergravity description of the IR Klebanov-Strassler solution lead to a 4d Topological Field Theory (TQFT) in the boundary, which saturates the mixed anomaly.

First Talk

• Title: On the Finiteness of Supergravity Landscape in d=6

• Abstract: In the past years, it has been well established that UV quantum gravity theory puts strict constraints on the set of quantum field theory that can appear in the low- energy. Such consistency conditions are said to divide the consistent quantum field theories to those in the Landscape (consistent when coupled to gravity) and those not consistent which are said to belong to the Swampland. I will start by reviewing such conditions in the context of supersymmetric theories and evaluate where we stand on the validity of the String Lamppost Principle, i.e. the idea that all consistent quantum gravitational theories are part of the string theory landscape. I will particularly focus on our recent work with Cumrun Vafa where we argue that there is an upper bound on the number of massless modes in d=6, consistent with the String Lamppost Principle.

Second Talk

• Title: The Standard Model Quiver from Singular de Sitter String Compactifications

• Abstract: With the advent of the string landscape, the realisation of the Standard Model in general string theory compactifications to 4D has become a primary focus. This talk concerns novel constructions of the Standard Model in global set-ups of type IIB Calabi-Yau compactifications. We argue that the Standard Model quiver can be embedded into Calabi-Yau threefolds through orientifolded D3 branes at del Pezzo singularities dPn with n ≥ 5. To illustrate our approach, we construct several distinct local dP5 models via a combination of Higgsing and orientifolding. This procedure reduces the original dP5 quiver gauge theory to the Left-Right symmetric model with three families of quarks and leptons and a Higgs sector to further break the symmetries to the Standard Model gauge group. Subsequently, we discuss explicit embeddings of the local model in a global Calabi-Yau compactification. We show that moduli can be stabilised in 4-dimensional de Sitter vacua with uplifting provided by T-branes.

First Talk

• Title: Probing inflation with the stochastic gravitational wave background and an opportunity for string pheno

• Abstract: Primordial scalar fluctuations sourced during inflation, if sufficiently enhanced, induce a contribution to the stochastic gravitational wave background that is potentially detectable with the upcoming generation of gravitational wave observatories. This enhancement requires a departure of inflation from the vanilla single-field slow-roll paradigm and e.g. occurs in models with features in the inflaton potential or due to multi-field dynamics. These properties necessary for an enhancement are generically present in string theory compactifications. String theory constructions can thus help in constraining such more complicated inflation models from the theory side, which is a task with interesting connections to the swampland program.

Second Talk

• Title: Branes, fermions and superspace

• Abstract: We provide an approach to obtain the fermionic expansion of brane actions and specialise in four-fermion terms. For doing so, we use the interpretation of branes being hypersurfaces in superspace, and obtain the fermion expansion in the most simple case: the M2-brane. Next, we use a superspace generalization of dimensional reduction and of T-duality to obtain fermion terms on all Dp-branes.

First Talk

• Title: Vanishing Yukawa couplings in heterotic compactifications

• Abstract: We consider the perturbative Yukawa couplings of effective field theories obtained from compactifications of the heterotic string on Calabi-Yau three-folds. Although the physical Yukawa coupling explicitly depends on the Calabi-Yau metric, it has been known since the 80s that there is a factor that is independent of this metric. This so-called holomorphic Yukawa coupling only depends on the cohomology classes of the moduli and the (perturbative) physical coupling must vanish whenever the holomorphic coupling does. While considerably simpler, the holomorphic coupling is still subtle to compute because it depends on a multiplicative structure on cohomology. Fortunately, in certain compactifications, geometric structures of the manifold impose constraints on the allowed non-vanishing holomorphic couplings, and this has led to vanishing theorems in the past. In this talk, recent work will be presented in which vanishing theorems with a much wider range of applicability than their precursors are derived. This is based on results from homological algebra and sheaf cohomology, which will be briefly reviewed before we present the arguments that lead to the new results. As far as time allows, examples will be presented demonstrating that the new theorems do indeed predict new vanishings, relative to older results.

Second Talk

• Title: Dynamical tadpoles, stringy cobordism and the SM from spontaneous compactification

• Abstract: We consider string theory configurations with tadpoles for dynamical fields and discuss properties of the resulting spacetime-dependent solutions. We argue that these solutions can extend only a finite distance away in the spacetime dimensions over which the fields vary, with a scaling controlled by the strength of the tadpole. We also show that naive singularities arising at this distance scale are replaced by ends of spacetime, related to the cobordism defects of the swampland cobordism conjecture. We illustrate these phenomena in several examples, including susy and non-susy 10 string theories and a 6d string model whose tadpole triggers spontaneous compactification to a semirealistic 3-family MSSM-like particle physics model.

First Talk

• Title: The Gravitino and the Swampland

• Abstract: We conjecture that the limit of vanishing gravitino mass belongs to the swampland, since it corresponds to the massless limit of an infinite tower of states and thus to the breakdown of the effective field theory. We test our proposal in large classes of models coming from compactification of string theory to four dimensions, where we identify the Kaluza-Klein nature of the tower of states becoming light. We point out a general relation between the gravitino mass and gauge coupling in models with extended supersymmetry, which can survive also in examples with minimal supersymmetry. This allows us to connect our conjecture to other well established swampland conjectures, such as the weak gravity conjecture or the absence of global symmetries in quantum gravity. We discuss phenomenological implications of our conjecture in (quasi-)de Sitter backgrounds and extract a lower bound for the gravitino mass in terms of the Hubble parameter.

First Talk

• Title: Eternal Inflation and (Anti) de Sitter Bounds from Dimensional Reduction

• Abstract: In recent years, much work has gone into understanding the implications of a set of interesting but more speculative Swampland conjectures, among which are the de Sitter conjectures and the (Anti) de Sitter distance conjecture. In order to place these statements on firmer ground and understand their domains of validity, it is crucial to understand the physical underpinning of these statements, and (relatedly) to fix presently unknown O(1) coefficients appearing in them. In this talk, we will see how dimensional reduction may play a useful role in this process, in that it distinguishes particular, physically-meaningful values of O(1) coefficients. We will also work out the conditions for slow-roll eternal inflation, and will we compare these bounds to the de Sitter conjecture bounds.

Second Talk

• Title: The Gravitino Swampland Conjecture

• Abstract: We extend the swampland from effective field theories (EFTs) inconsistent with quantum gravity to EFTs inconsistent with quantum supergravity. This enlarges the swampland to include EFTs that become inconsistent when the gravitino is quantized. We propose the Gravitino Swampland Conjecture (GSC): the gravitino sound speed must be non-vanishing in all EFTs that are low energy limits of quantum supergravity. This seemingly simple statement has important consequences for both theories and observations. Talk based on arXiv:2102.10113 and arXiv:2103.10437.

First Talk

• Title: Non-flat elliptic fourfolds, three-form cohomology and strongly coupled theories in four dimensions

• Abstract: In this talk we consider elliptic fourfolds with non-minimal singularities in codimension two in the base. These sectors admit an F-theory interpretation as compactifications of 6D superconformal matter on a Riemann surface. We consider resolutions of those non-minimal singularities which sacrifice flatness of the fibration and naturally leads to threeform cohomology in terms of the 6D SCFT data. Finally we consider a Higgs and Coulomb branch type of conifold transition. The former one pushes the non-flat fiber one codimension lower and leaves non-perturbative four-point matter coupling as a remnant. The second transition removes those fibers via a birational base blow-up which keeps the Euler number invariant.

Second Talk

• Title: String defects, supersymmetry and the swampland

• Abstract: In order to fully connect the swampland program and low-energy phenomenology, it appears necessary to consider the conjectures in string models with broken supersymmetry. In this talk, I will consider an approach pioneered by Kim, Shiu and Vafa, who ruled out anomaly-free supergravity theories based on the fact that they cannot be consistently coupled to a complete spectrum of string defects. To possibly extend their conditions, expressed in a pure effective theory language, to non-SUSY setups, I will discuss their origin in a microscopic string picture, namely perturbative 6d orientifold constructions, and study how they are modified in SUSY breaking setups of the brane supersymmetry breaking type. In the latter case, the supersymmetric conditions still hold if the string defect does not overlap with the SUSY breaking source. The general discussion also suggests a “null string conjecture”, that allows to exclude some 6d supergravity theories that have no known string or F-theory realization.

First Talk

• Title: The Price of Curiosity: Information Recovery in de Sitter Space

• Abstract: Recent works have revealed that the fine-grained entropy of a non-gravitating subsystem, when entangled with a gravitating region, can receive contributions from so-called quantum extremal islands. Applied to black holes, this reproduces the unitary Page curve for Hawking radiation. In this talk, I will show how these results can be applied to the thermal radiation measured by a static observer in de Sitter space. Focusing on JT gravity, I will emphasize the necessity of going beyond the thermal equilibrium of the Bunch-Davies state. We will see that a quantum extremal island can contribute to the fine-grained entropy, suggesting unitarity of the radiation, but this comes at a price: when the island appears a singularity forms that a static observer will eventually hit.

Second Talk

• Title: Anomalies of (0,4) SCFTs from wrapped D3 branes in F-theory

• Abstract: In this talk we will consider macroscopically, a class of 2d (0,4) SCFTs living on black strings. The black strings are constructed by wrapping D3-branes on a curve inside the base of a (singular) elliptically fibered Calabi—Yau three-fold. The asymptotic geometry in which the branes live in includes an ALE or ALF space which probes the D3 branes. Using macroscopic computations we will compute the various anomaly coefficients of the theory by reducing 6d N=(1,0) supergravity on the horizon of the black strings and extracting the coefficients of Chern—Simons terms. As we will, see the inclusion of one-loop corrections from integrating out massive modes is essential. Given time we will make some comments on the microscopic computation.

First Talk

• Title: Algorithmically solving the Tadpole Problem

• Abstract: I demonstrate how to use differential evolutionary algorithms to find flux compactifications of M-theory on K3xK3. The assumption that a large numbers of moduli can be stabilized with fluxes within the tadpole bound is one of the corner stones of the String Landscape and was recently challenged by the Tadpole Conjecture. Explicitly showing moduli stabilization for manifolds with many moduli is highly challenging. On K3xK3 moduli stabilization is well understood and can be formulated exclusively in terms of integer matrices and their eigenvalues and -vectors. In particular, there is no knowledge of complicated period integrals or the corresponding Picard-Fuchs equations required. This makes this example predestined for a computer aided search. Using differential evolution we show that there are no smooth compactifications on K3xK3 with arbitrarily small flux M2-charge, in tension with the tadpole bound.

Second Talk

• Title: Tackling the SDC in AdS with CFTs

• Abstract: Using the AdS/CFT correspondence, questions related to the Swampland Distance Conjecture (SDC) in AdS can be reformulated in the language of conformal manifolds. For AdS_5 backgrounds with eight or more supercharges, we find that for a large class of (and possibly all) infinite-distance points, there must exist a tower of massless higher-spin fields. On the conformal side, those points are those for which a sector of the CFT becomes free, and the tower follows from the presence of higher-spin conserved currents. We illustrate these results for type IIB compactifications on S^5 and its orbifolds.

First Talk

• Title: New databases for model building: CICY orientifolds and GV invariants

• Abstract: We present two recently computed explicit databases which could be relevant for model building in String Phenomenology. The first contains two million orientifolds supporting O3 and O7 planes that can be constructed for the list of Complete Intersection Calabi-Yau manifolds (CICYs). The second is an explicit computation of all the genus zero Gopakumar-Vafa (GV) invariants for such class of CYs, up to total degree 10. In both instances, we find interesting phenomena arising. In the orientifold scan, we discover a plethora of new cases with non-vanishing h11-odd, which can support C2 and B2 axions, as well as thraxions. We also observe the existence of conifold singularities that lie on-top of orientifold planes and thus cannot be deformed, but can still be resolved. We argue that on the resolution side we find a vast set of (possibly previously unknown) CY manifolds. In the GV scan, we find interesting hierarchies between the rate of growth of the invariants along different directions inside the Picard lattice. Such hierarchies have an application in complex structure moduli stabilization aiming at achieving a very small W0 superpotential, as well as winding inflation models. Furthermore, we eliminate redundancies in the list of CICYs, by a systematic implementation of Wall’s theorem.

Second Talk

• Title: The Convex Hull Swampland Distance Conjecture and Bounds on Non-geodesics

• Abstract: The Swampland Distance Conjecture (SDC) restricts the geodesic distances that scalars can traverse in effective field theories as they approach points at infinite distance in moduli space. We propose that, when applied to the subset of light fields in effective theories with scalar potentials, the SDC restricts the amount of non-geodesicity allowed for trajectories along valleys of the potential. This is necessary to ensure consistency of the SDC as a valid swampland criterium at any energy scale across the RG flow. We provide a simple description of this effect in moduli space of hyperbolic space type, and products thereof, and obtain critical trajectories which lead to maximum non-geodesicity compatible with the SDC. We recover and generalize these results by expressing the SDC as a new Convex Hull constraint on trajectories, characterizing towers by their scalar charge to mass ratio in analogy to the Scalar Weak Gravity Conjecture. We show that recent results on the asymptotic scalar potential of flux compatifications near infinity in moduli space precisely realize these critical amounts of non-geodesicity. Our results suggest that string theory flux compactifications lead to the most generic potentials allowing for maximum non-geodesicity of the potential valleys while respecting the SDC along them. Based on arXiv:2012.00034 with Angel M. Uranga and Irene Valenzuela.

First Talk

• Title: Neural Network Approximations for Calabi-Yau metrics

• Abstract: Ricci flat metrics for Calabi-Yau threefolds are not known analytically. In this work, we employ techniques from machine learning to deduce numerical approximations to flat metrics for the Fermat quintic, for the Dwork quintic, and for the Tian-Yau manifold. This investigation employs a single neural network architecture that is capable of approximating Ricci flat Kaehler metrics for several Calabi-Yau manifolds of dimensions two and three. We show that measures that assess the Ricci flatness of the geometry decrease after training by three orders of magnitude. This is corroborated on the validation set, where the improvement is more modest. Finally, we demonstrate that discrete symmetries of manifolds can be learned in the process of learning the metric.

Second Talk

• Title: de Sitter Quantum Breaking, Swampland Conjectures and Thermal Strings

• Abstract: We argue that the quantum breaking approach and the trans-Planckian censorship conjecture can both lead to bounds of the same functional form for the scalar potential. The proposal that dS quantum breaking is induced by tracing over states beyond the dS horizon gives rise to a thermal matter component, which can be straightforwardly generalized to string theory. Imposing a censorship of quantum breaking, we recover in the low temperature regime the no eternal inflation bound. The stronger dS swampland conjecture bound arises, under certain assumptions, in the mysterious high temperature regime of string theory.