Date : July 17, 2025
Speaker : Aditya Jain
Title :         Invariants and 3pt correlators in 4d N=1 SCFTs

Abstract :         We use auxiliary polarization spinors and the superinversion transformation to construct superconformally invariant structures in 4d N=1 SCFTs. These invariants are used to express general 3-point correlators of symmetric traceless superfield operators in terms of a few unknown OPE coefficients. Since these invariant structures have a definite parity, they amount to parity-even as well as parity-violating contributions to the 3-point SCFT correlators. We also impose the conservation (shortening) condition on the operators to restrict the form of correlators of supercurrents. In correlators containing identical supercurrents, we observe that the parity-even/odd structures vanish based on the spin of the operators. This talk is based on our recently published work [2411.01903].

Date : January 23, 2025
Speaker : Lucas Nogueira de Sá Martins
Title :         Supersymmetric string configurations in AdS_4 x S^5

Abstract :         In this talk, I will review the main idea of supersymmetric localization and its application in supersymmetric gauge theories to derive exact results at strong coupling. I will then focus on a specific prediction these results make about superstring theory, assuming Maldacena's conjecture holds. Finally, I will discuss the work in [2411.00211], where the pure spinor formalism was used to investigate whether supersymmetric localization can yield exact results on the superstring side of the AdS/CFT duality, aiming to confirm these predictions.

Date : December 12, 2024
Speaker : Leonardo Pipolo de Gioia
Title :         Flat connections on minimal surfaces and the area problem

Abstract :         TBA

Date : December 5, 2024
Speaker : Nathan Berkovits
Title :         Equivalence proof of pure spinor and Ramond-Neveu-Schwarz amplitudes

Abstract :         A new manifestly spacetime-supersymmetric prescription for superstring amplitude computations is given using the pure spinor formalism which does not contain subtleties from poles in the pure spinor ghosts. This super-Poincar´e covariant prescription is related by a U(5)-covariant field redefinition to the Ramond-Neveu-Schwarz amplitude prescription where the pure spinor parameterizes the choice of SO(10)/U(5). For F-term scattering amplitudes which preserve a subset of the spacetime supersymmetries, the new pure spinor amplitude prescription reduces to the previous pure spinor prescription.  

Date : November 28, 2024
Speaker : Eduardo Casali
Title :         Topological N=4 inspired twistor string

Abstract :         I will talk about some tentative ideas on how to construct a string theory in twistor space that describes self-dual Einstein gravity. While there are twistor string theories that describe conformal self-dual gravity, Einstein gravity from twistor space has been elusive. I will explain why that is so, what is the structure we expect from a twistor string that describes self-dual Einstein gravity and their relation to the N=4 topological string. Eventually we want to study the open-closed duality for this string theory in a similar fashion to the work of Costello, Paquette & Sharma.

Date : November 21, 2024
Speaker : Rodrigo Schmidt Pitombo
Title :         A twisted bootstrap for AdS3-CFT2

Abstract :         The correspondence between chiral algebras and superconformal field theories (SCFTs) through a "twisting" procedure has been known since the work of C. Been et al. [1]. In general, the chiral algebra captures the dynamics of protected subsectors of SCFTs, which is extremely useful in the paradigmatic examples of AdS-CFT, as the supergravity states correspond to protected operators in the boundary theory. In this talk, I will discuss how one can use this correspondence to set up a bootstrap procedure on the chiral algebra that yields non-trivial information about the dual supergravity theory. In particular, I will show how we used this to obtain all 3-point functions of IIB SUGRA in AdS_3 X S^3 X K3 and argue that we can use them to extend the results of [2].

[1] Beem, C., Lemos, M., Liendo, P. et al. Infinite Chiral Symmetry in Four Dimensions. Commun. Math. Phys. 336, 1359–1433 (2015)

[2] Behan, C., Pitombo, R.S. Mellin amplitudes for AdS3 × S3. J. High Energy Phys. 2024, 59 (2024). https://doi.org/10.1007/JHEP11(2024)059

Date : November 7, 2024
Speaker : Edvard Musaev
Title :         Families of CFTs from the M-theory perspective

Abstract :           Conformal field theories are known to describe fixed points of various quantum fields theories appearing there as standalone theories or as families of CFTs related by a deformation by exacty marginal operators. On the gravity side of the hologaphic correspondence these  manifest themselves as AdS solutions or as domain wall like solutions interpolating between two AdS fixed points. In this talk both situtations will be considered with the most emphasis given to the former  in the context of the recently suggested formalism of polyvector deformations.

Date : October 31, 2024
Speaker : Kostas Skenderis
Title :         Flat-space scattering amplitudes from CFT correlators

Abstract :           I will discuss how to obtain flat-space scattering amplitudes in d-dimensions by taking a limit of (d-1)-dimensional CFT correlators. This can be understood as taking a flat-space limit of AdS and using the AdS/CFT correspondence. I will exemplify the discussion with the scattering amplitude of an Abelian gauge field with two massive vector fields.

Date : October 17, 2024
Speaker : Hao-Lan Xu
Title :         Analyticity properties of 2d Ising field theory

Abstract :          In this talk, I will discuss the analyticity properties of 2d Ising field theories (IFTs). I will start with a short introduction to 2d Ising field theory, which is the continuous limit of the 2d Ising model on square lattice, and can be understood as relevant deformations of 2d Ising CFT. The different scenarios for high-T and low-T regime will be introduced, with IFT having different analytic properties in these theory spaces. I will focus on the analyticity of the first mass (M_1, also the inverse correlation length), and discuss its critical behaviours and dispersion relations in both ordered and disordered phases. Finally, the extended analyticity conjecture of M_1 will be introduced, stating that the high-T phase is "hiding" behind the Fisher-Langer's branch cut of low-T, and the Yang-Lee singularity should be understood as the exact spinodal singularity.

Date : October 10, 2024
Speaker : Andrei Mikhaylov
Title :         AdS deformations and exact sequences

Abstract :         In AdS/CFT computations, we extensively use the fact that physical quantities are invariants of the superconformal symmetry. Besides invariants, we can compute cohomologies. They become important when we consider deformations of AdS transforming in non-unitary representations. I will discuss some example where nontrivial extensions of representations of the superconformal algebra play a role in AdS pure spinor computations.

Date : October 3, 2024
Speaker : Connor Behan
Title :         A status report on the modular bootstrap

Abstract :         Along with the infinite dimensional Virasoro algebra, conformal field theories in two dimensions obey a number of additional constraints when they are defined on non-trivial Riemann surfaces. These are the constraints of modular invariance which lead to some surprising connections between physics and number theory. More recently, via the AdS/CFT correspondence, modular invariance has become an important tool for studying "pure" quantum gravity in three dimensions. I will review these developments while discussing two modern papers --- one about rational CFTs and the other about irrational CFTs.

References: 2107.13557, 2208.02259

Date : September 19, 2024
Speaker : Rodrigo Schmidt Pitombo
Title :         Mellin amplitudes for AdS3 x S3

 
Abstract :     Over the last few years, the language of Mellin amplitudes has been ubiquitous in bootstrap procedures for correlation functions in holographic superconformal field theories (SCFTs). Its usefulness mainly stems from its analytic properties, which are reminiscent of those of scattering amplitudes in flat space. For example, all 4-point functions for all maximally supersymmetric SCFTs at strong coupling, in dimensions between 3 and 6, were obtained with Mellin space methods. Due to its pathologies, the two-dimensional case evaded a systematic and efficient bootstrap algorithm in Mellin space for some time. In this talk, I will discuss the paper 2408.17420, which shows how to adapt the well-known Mellin machinery to two dimensions. Then, I'll explain how to use superconformal symmetry together with input from supergravity to completely fix 4-point functions in the paradigmatic 2D holographic theory: The D1-D5 CFT, dual to IIB superstrings in AdS3XS3.

Date : September 12, 2024
Speaker : Cassiano Daniel
Title :         A covariant three-point amplitude of half-BPS states in AdS

 
Abstract :     Using the PSU(1,1|2) hybrid formalism, I will talk about a superstring three-point amplitude of half-BPS states inserted in the AdS_3 boundary

Date : August 29, 2024
Speaker : Aki Hashimoto
Title :         Path integral of free fields and determinant of the Laplacian

 
Abstract :     I consider Eucledianized AdS3 with periodic time coordinate. The spectrum of normal modes on AdS3 is well known, and the partition function of a scalar field on EAdS3 is expected to agree with the thermal partition function of these normal mode states. The path integral of a scalar field is also expected to agree with the determinant of Klein-Gordon operator on EAdS3, except that it does not. I will describe how they do not agree, and trace the origin of the discrepancy to the fact that time coordinate in AdS3 is warped. I will also comment on implication to perturbative quantum gravity and quantum black hole issues. 

Date : August 22, 2024
Speaker : Denis Karateev
Title :         Correlation functions in weakly relevant flows

 
Abstract :     We study abstract weakly relevant flows in a general number of dimensions. They arguably provide the simplest example of renormalization group (RG) flows between two non-trivial fixed points. We compute several two-point correlation functions in position space valid along the whole RG flow. This is done by using conformal perturbation theory together with the solution of the Callan-Symanzik equation. From the explicit expressions of the two-point functions of conserved currents and the stress-tensor we extract the change in the central charges between the UV and IR fixed points.

Date : June 06, 2024
Speaker : Remann Lipinski
Title :         Interplay between chiral strings and field theory

 
Abstract :     I will present an informal overview on chiral string theories, including recent developments. They can be seen as a tensionful version of the ambitwistor string, and provide a bridge between conventional strings and field theory.

Date : May 29, 2024
Speaker : Harish Murali
Title :         Huge 1/2- BPS operators and Fluid Dynamics in N=4 SYM

 
Abstract :    I will talk about structure constants of 1/2 BPS operators that scale as O(N^2) at large N. These quantities can be cast as matrix integrals whose large N limit reduces to the EOM of an integrable fluid. I will present methods to solve the problem for a large class of 1/2 BPS operators.

Date : May 23, 2024
Speaker : Sabrina Pasterski
Title :         Radiation in Holography

 
Abstract :     We show how to encode the radiative degrees of freedom in 4-dimensional asymptotically AdS spacetimes, using the boundary Cotton and stress tensors. Background radiation leads to a reduction of the asymptotic symmetry group, in contrast to asymptotically flat spacetimes, where a non-vanishing news tensor does not restrict the asymptotic symmetries. Null gauges, such as Λ-BMS, provide a framework for AdS spacetimes that include radiation in the flat limit. We use this to check that the flat limit of the radiative data matches the expected definition in intrinsically asymptotically flat spacetimes. We further dimensionally reduce our construction to the celestial sphere, and show how the 2-dimensional celestial currents can be extracted from the 3-dimensional boundary data.

Date : May 09, 2024
Speaker : Panagiotis Marinellis
Title :       Waveforms from Scattering Amplitudes and Modified Gravity for spinning bodies

 
Abstract :        The detection of gravitational waves by the LIGO-VIRGO collaboration has marked a transformative era in astronomy, providing unprecedented insights into the cosmos and opening new avenues for exploring the universe. At the same time, advances in the classical limit of scattering amplitudes, notably through the KMOC formalism, have opened up new avenues for understanding compact binary systems. In this talk, we delve into the significance of these advances and explore the emergence of waveforms derived from scattering amplitudes. Theoretical underpinnings are elucidated, offering insights into the dynamics of binary systems and valuable tools for characterizing gravitational wave emissions. 

              Complementing waveforms derived from scattering amplitudes, we delve into the interplay of modified gravity theories with radiation losses in spinning binary systems, including computations in a QED toy model of modified gravity. We examine deviations from Einstein's theory on waveforms, shedding light on modified gravity's effects. Through theoretical analyses, we unveil how alternative gravity theories manifest, offering insights into fundamental physics and new testing avenues.

Date : May 02, 2024
Speaker : Zechuan Zheng
Title :         Bootstrap for Finite N Lattice Yang-Mills Theory

 
Abstract :       We introduce a comprehensive framework for analyzing finite N lattice YangMills theory and finite N matrix models. Utilizing this framework, we examine the bootstrap approach to SU(2) Lattice Yang-Mills Theory in 2,3 and 4 dimensions. The SU(2) Makeenko-Migdal loop equations on the lattice are linear and closed exclusively on single trace Wilson loops. This inherent linearity significantly enhances the efficiency of the bootstrap approach due to the convex nature of the problem, permitting the inclusion of Wilson loops up to length 24. The exact upper and lower margins for the free energy per plaquette, derived from our bootstrap method, demonstrate good agreement with Monte Carlo data, achieving precision within 0.1% for the physically relevant range of couplings in both three and four dimensions. Additionally, our bootstrap data provides estimates of the string tension, in qualitative agreement with existing Monte Carlo computations.

Date : Apr 11, 2024
Speaker : Pinaki Banerjee
Title :         Stringy Regge limit @1-loop

 
Abstract :        I'll talk about the high energy limit of 2 -> 2 strings scattering at 1-loop with fixed momentum transfer. This is known as the Regge limit. This limit is explored by two different methods : unitarity cuts and saddle-point analysis. Although standard Regge theory works for the closed string scattering, the  field theory intuition partially breaks down  for the open-string case, depending on the topology of the diagram. Furthermore, for the planar open-string scattering the leading contribution is simpler and can be extracted to arbitrary loop order.  When resummed in a certatin limit, it shows the leading Regge trajectory remains linear.  

Date : Apr 04, 2024
Speaker : Horatiu Nastase
Title :        3-point functions of currents for holographic cosmology and monopole non-Gaussianities

 
Abstract :        

Date : Mar 28, 2024
Speaker : Leonardo Pipolo de Gioia
Title :       Celestial amplitudes from Lorentzian conformal correlators

 
Abstract :        The Celestial Holography conjecture posits the existence of a codimension two theory capable of computing the S-matrix in a conformal primary basis. Although resembling a CFT in several respects, the intrinsic definition of this proposed dual theory remains elusive. In this talk, I will discuss a conjecture suggesting that Celestial CFT (CCFT) is related to a dimensionally reduced CFT on the Lorentzian cylinder and present some concrete examples of celestial amplitudes constructed in this way.

Date : Mar 21, 2024
Speaker : Murat Koloğlu
Title :         Quantum Detectorology 

 
Abstract :         I will talk about asymptotic detector operators describing possible measurements performed at null infinity. I will discuss how to define them in terms of light-ray operators, how to compute their matrix elements, and how to renormalize them in weakly-coupled field theories. I will apply this framework to Wilson-Fisher theory as an explicit example, recovering known results, resolving some puzzles, and discovering some novel findings about Regge trajectories. Finally, I will discuss detectors in asymptotically-flat Einstein gravity and present work in progress on the first computation of quantum 2- and 3-point energy correlators in a gravitational theory.

Date : Mar 21, 2024
Speaker : Vinícius Bernardes
Title :       A two parameter family of hyperbolic string vertices

 
Abstract :        String vertices are fundamental objects in string field theory: they define Feynman rules through a decomposition of the moduli space of Riemann surfaces. I will talk about a two-dimensional generalization of the hyperbolic string vertices, defined for both open and closed strings. For closed strings, this family provides an interpolation between the lightcone vertex (which is cubic but not Lorentz covariant), and the polyhedral vertices (which are covariant but not cubic).

Date : Mar 14, 2024
Speaker : Pietro Ferrero
Title :         On the supergravity description of non-critical string theories

Abstract :        We revisit the old question of how non-critical string theories can be used to study gauge theories using holography. To this end, focusing on supersymmetric cases, we first establish which gauged supergravity provides the correct "low energy" description for such string theories with a precise matching of the “massless” spectrum on a linear dilaton background. We then proceed to study supersymmetric solutions in gauged supergravity, which conjecturally represent configurations of D-branes of the non-critical string theory. These are supposed to provide the holographic dual of certain 3d and 4d gauge theories with eight supercharges, ranging from pure super Yang-Mills theory to super conformal QCD. The talk is based on work in progress with Leonardo Rastelli and Andrea Dei.

Date : Mar 14, 2024
Speaker : Rodrigo Pitombo
Title :       Towards the AdS Virasoro-Shapiro Amplitude

 
Abstract :         The Virasoro-Shapiro (VS) amplitude is the tree-level scattering amplitude between 4 massless closed strings and in AdS it is dual to a 4-point function of half-BPS operators to order 1/N^2. This is a hard problem in both sides of AdS/CFT as it involves non-perturbative physics in N=4 SYM and we don't yet know how to properly compute superstring amplitudes in AdS_5. In this talk, I will show how to properly define these amplitudes in terms of CFT correlators and review a series of papers by Fernando Alday and collaborators in which CFT bootstrap techniques are used together with a string-theory-inspired ansatz to completely fix the VS Amplitude to first order in a near-flat expansion.

References : https://arxiv.org/abs/2305.03593 , https://arxiv.org/abs/2204.07542 , https://arxiv.org/abs/2209.06223 , https://arxiv.org/abs/2306.12786

Date : Mar 07, 2024
Speaker : Pedro  Vieira
Title :        Fluids for Matrix Models for Huge Operators in AdS/CFT

 
Abstract :        

Date : Feb 29, 2024
Speaker : Nathan  Berkovits
Title :         On the equivalence of the pure spinor and Ramond-Neveu-Schwarz formalisms of the superstring

 
Abstract :        I will discuss the relation of the scattering amplitude prescriptions in the RNS and pure spinor superstring formalisms.

Date : Feb 01, 2024
Speaker : Dario Rosa
Title :         Describing large Hilbert spaces: from matrix product states to neural quantum states

 
Abstract :         We will review the standard problem in quantum many-body systems arising from the exponential growth of the Hilbert space with the number of particles, and we will discuss methods to deal with this challenge. At first, we will see how matrix product states allow to approximate states characterized by area-law entanglement. We will then turn to the recent proposal of neural quantum states as an effective way to approximate states characterized by volume law entanglement, that cannot be efficiently approximated with matrix product states.

Date : Nov 23, 2023
Speaker : Gabriel Menezes
Title :         Compton Scattering in String Theory

Abstract :         Scattering amplitudes and QFT methods have been applied successfully to understand in an alternative perspective the general relativistic two-body problem, notably in the calculation of the gravitational potential between two masses. In particular, classical contributions to the 2PM amplitude are controlled by the opposite-helicity Compton amplitude. However, it is well known that such amplitudes may develop unphysical poles when the spin of the massive particle exceeds the spin of the emitted messengers. In this talk we will explore the startling possibility that string theory may present an interesting solution to this issue.

Date : Nov 16, 2023
Speaker : Andrei Mikhailov
Title :       Yang-Mills algebra and symmetry transformations of vertex operators

Abstract :         Linearized solutions of SUGRA equations of motion are described in the pure spinor formalism by vertex operators. Under supersymmetry transformations, they transform covariantly only up to BRST exact terms. We identify the cohomology class which is responsible for that. Computations are simplified by using the formalism of quadratic algebras.

Date : Nov 01, 2023
Speaker : Eduardo Casali
Title : Flat space holography and twistors

Abstract :         

Date : Oct 26, 2023
Speaker : Alexey Sharapov
Title : Poisson electrodynamics and symplectic groupoids

Abstract :         Poisson electrodynamics represents the low-energy (or semi-classical) limit of the non-commutative U(1) gauge theory. I will present a new approach to Poisson electrodynamics based on the geometry of symplectic groupoids integrating a given Poisson manifold. From a physical point of view, a symplectic groupoid is just the phase space of a point particle in non-commutative space-time and gauge fields are identified with the group of bisections of a groupoid. The natural action of bisections on a symplectic groupoid allows one to define the minimal coupling of a charged particle with an electromagnetic field. Unlike usual classical mechanics, the momentum space of a particle appears curved (or even compact), which can lead to dramatic physical consequences.

Date : Oct 19, 2023
Speaker : João Gomide  
Title : B-RNS-GSS superstring in Ramond-Ramond backgrounds

Abstract :    The recently established B-RNS-GSS formalism shares features of the pure spinor, RNS and Green-Schwarz-Siegel formalisms for the superstring. Most notably, it has manifest spacetime supersymmetric and is quantized via a N=(1,1) worldsheet superconformal BRST charge with superconformal generators (G,T;Gbar,Tbar). In this talk, I will discuss recent work that extends this formalism to the description of Type II backgrounds by showing that the classical anticommutation relations {G,G}=-2T and {Gbar,Gbar}=-2Tbar recover the Type II supergravity equations of motion. As an application, I will also present an action and Lax connection for the string on an AdS_5xS^5 background.

Reference:   https://arxiv.org/abs/2310.02182

Date : Oct 05, 2023
Speaker : Connor Behan
Title : Recent progress in localization for non-Lagrangian theories

Abstract :    4d gauge theories with N=2 supersymmetry provide a rich playground for exact results as shown by Seiberg and Witten in 1994. Their techniques were significantly streamlined in the 2000s with the introduction of localization which operates directly on the path integral. Even more recently, localization has been combined with the conformal bootstrap thereby shedding light on unprotected operators. A natural next step is to apply this, not just to gauge theories themselves, but to infrared phases of these theories which live at singular points of the moduli space. The fact that these CFTs are non-Lagrangian brings additional challenges which are the focus of the recent paper I will discuss. 

Reference :      https://arxiv.org/abs/2306.05141

Date : Sep 14, 2023
Speaker : Andres Anabalon
Title : Supersymmetric AdS Solitons

Abstract :  I will discuss a recent generalization of the AdS Soliton to support nontrivial Killing Spinors.  Based on :

1.  Supersymmetric solitons and a degeneracy of solutions in AdS/CFT  

2. Supersymmetric solitons in gauged $\mathcal{N}=8$ supergravity