Past talks 2024
17/12/24
Title: Transcendentality and two-point functions of supersymmetric operators
Abstract: We present evidence that perturbative two-point functions of certain supersymmetric operators in N=4 SYM and the ABJM model exhibit uniform transcendentality. For N=4 SYM we propose an all-order expression for the leading term in dimensional regularization. In three dimensions, we leverage the uniform transcendentality conjecture to streamline the analytic reconstruction of the expansion of three-loop master integrals in dimensional regularization. The conjecture allows to express them as rational combinations of bases of Euler sums of fixed transcendental weight. The gain, compared to a basis with mixed transcendental weights, asymptotes the golden ratio. If you did not understand anything in this abstract, especially the latter part, worry not! It is easier and more entertaining than it sounds, and we will explain all the jargon.
References: arXiv:2410.23395 [hep-th]
03/12/24
Title: Bootstrapping line defects in AdS3/CFT2
Abstract: Over the last decades, line defects have proven to be a very useful laboratory to study and develop non-perturbative methods in the context of holographic dualities. Despite the remarkable progress in the analysis of these defects in the framework of the AdS5/CFT4 and AdS4/CFT3 correspondences, much less is known about their properties in the AdS3/CFT2 case. In this talk I will present the results of 2410.02685, where we addressed this question by performing an analytic bootstrap analysis of 1/2 BPS line defects in the holographic dual to type IIB string theory in AdS3xS3xT4 with mixed Ramond-Ramond and Neveu Schwarz-Neveu Schwarz three-form flux. We studied two-, three- and four-point functions of the displacement and tilt supermultiplets up to next-to-leading order in their strong-coupling expansion, obtaining a bootstrap result that only depends on two parameters. Furthermore, we performed a Witten diagram check of these results, providing an holographic interpretation for the parameters that are not constrained by the bootstrap analysis.
References: arXiv:2410.02685 [hep-th]
12/11/24
Title: Exploring Defects with Degrees of Freedom in Free Scalar CFT
Abstract: Defects in conformal field theories are interesting objects to study from both formal and applied points of view. In this talk, I will discuss how to construct conformal defects in free scalar field CFTs in diverse dimensions, considering both quadratic cases and those involving defect interactions. The latter can be realized by coupling the bulk free scalar to lower dimensional theories, including the unitary family of minimal models M(p, p+ 1). Additionally, I will consider monodromy defects associated with a global U(1) flavour symmetry, where one can study both self-defect interactions and couplings to Minimal Models.
References: arXiv:2410.01716 [hep-th]
08/10/24
Title: Aspects of gauge-strings duality
Abstract: I will explain some recent works where we are proposing models of CFTs that after a deformation flow into gapped QFTs. The presence of many flavours (fields in the fundamental representation of the gauge group) adds many interesting subtleties into the dynamics.
The presentation will be (hopefully) pedagogical, trying to emphasize on the main ideas and techniques. It will be based on the papers I wrote in the last year or so, with a generous review of things, attempting to get the feedback of the audience.
References:
27/09/24
Title: Auxiliary Field Deformations of Sigma Models and T-Duality
Abstract: In this talk, I will explain how to construct an infinite family of classically integrable deformations of the principal chiral model (PCM) using auxiliary fields. This class of theories includes deformations of the PCM by any function of the stress tensor, such as TT and root-TT. An advantage of this formalism is that it facilitates a straightforward analysis of the non-Abelian T-duals of these models, all of which are related to their pre-T-duality cousins by the same canonical transformation, and are thus also classically integrable.
References: arXiv:2408.09714 [hep-th], arXiv:2407.16338 [hep-th], arXiv:2407.11636 [hep-th]
04/07/24
Title: Localization and resummation in 2d Yang-Mills theory
Abstract: 2d Yang-Mills is a solvable interacting gauge theory which has been analyzed from many perspectives. In this talk, I will report on our recent computation of the all-orders perturbative expansion of the partition function around higher critical points of the action. This is computed for arbitrary topologies through resummation of the lattice partition function. I will then
show how the same result can be obtained via non-standard supersymmetric localization, leading to a novel effective action which is itself a distribution rather than a function of the supersymmetric moduli.
References: arXiv:2403.00053 [hep-th]
06/06/24
Title: Identifying non-anomalous symmetries using SymTFTs
Abstract: A symmetry G of a 1+1d QFT with a non-trivial anomaly cannot be gauged. But G may have non-anomalous subgroups which can be gauged. Similarly, non-invertible symmetries can be anomalous. However, there could be non-anomalous "sub-symmetries" which can be gauged. In this talk, I will describe non-invertible symmetries and explain how to characterise their anomaly. I will introduce a 2+1d topological quantum field theory called the SymTFT. I will introduce a procedure to determine non-anomalous symmetries in 1+1d from the SymTFT. I will describe this procedure in explicit examples. This talk is based on https://arxiv.org/abs/2405.04619 with Pavel Putrov.
References: arXiv:2405.04619 [hep-th]
16/05/24
Title: Quantum holographic surface anomalies
Abstract: Surface operators are characterised by their conformal anomaly coefficients, the analog of the conformal anomalous dimension of local operators. In holography and for surface operators dual to minimal branes, it is well-known that the leading part of these anomalies coefficients is captured by the behavior of the brane near the boundary of AdS; a beautiful result due to Graham-Witten. In this talk, I will present a method to calculate the subleading contribution to these coefficients in the same spirit, by combining a near-AdS3 expansion with heat kernel techniques. Applying this method to M2-branes, we obtain the first "direct" calculation of the anomaly coefficients for (locally supersymmetric) surface operators of the 6d (2,0) theory. The results agree with the existing literature, providing a check of more indirect methods, and evidence that the M2-brane action can be treated semiclassically by incorporating quantum corrections.
References: 2311.14797 [hep-th]
02/05/24
Title: Mixed boundary conditions in AdS2
Abstract: I will review the role of boundary conditions in the holographic prescription to compute CFT correlation functions in the general case. Then, I will focus on the case of AdS2 fluctuations dual to certain Wilson lines in the ABJ(M) theory. The coupling of the AdS2 string worldsheet with a flat Kalb-Ramond field gives rise to certain mixed boundary conditions, which appear to be consistent with the conformal symmetry in the dual line defect.
References: 2312.13258 [hep-th]
11/04/24
Title: Two loop five point integrals: light, heavy and large spin correlators
Abstract: We will study correlation functions of single-trace operators in N=4 Super Yang-Mills in perturbation theory. We will consider correlators built of two distinct types of operators. One is the lightest operator of the theory, the ubiquitous 20' and the other is a heavy operator of infinity charge. We will review the vast chain of dualities that underline such correlation functions in the more well known case of four point functions and present our results in the uplift of these dualities for five point functions in perturbation theory. More precisely, we will evaluate novel conformal integrals that allow us to study the properties of five point functions of light and heavy operators at two-loops. From light correlators we will extract structure constants of up to two spinning operators for small and large values spin. For heavy correlators we will be able to study its physical properties under several OPE and light-cone limits.
References: 2401.06099 [hep-th]
21/03/24
Title: Interpolating Bremsstrahlung function in ABJM
Abstract: In ABJM theory, enriched RG flows between circular 1/6 BPS bosonic and 1/2 BPS fermionic Wilson loops (WLs) have been introduced in arXiv:2211.16501. In this talk I will show how to generalize such flows for WLs supported along the latitude contour, computing their renormalized VEVs up to two loops in perturbation theory. I will further generalize the relation between the latitude WL VEV and the Bremsstrahlung function, which holds at the fixed points, to generic points along the flow by defining an interpolating Bremsstrahlung function. The result will then be checked through the computation of a cusp anomalous dimension associated to an interpolating cusped Wilson line. I will show how, away from the conformal fixed points, the usual identity is broken in a controlled way by conformal anomaly. Finally I will show that, from a defect CFT perspective, the breaking of the identity is due to the appearance of an anomalous dimension for fermionic operators localized on the defect.
References: 2312.13283 [hep-th]
07/03/24
Title: Non-Relativistic M2-Branes and the AdS/CFT Correspondence
Abstract: In this talk I'll discuss a non-relativistic limit of ABJM that isolates half-BPS field configurations. We'll see that the non-relativistic theory has an exotic symmetry algebra, with the spatial symmetries enhanced to holomorphic transformations that can be taken to have arbitrary time-dependence. We will also consider a corresponding limit of the dual supergravity geometry that reduces the AdS4 factor to an AdS2. The symmetries can be matched on both sides, and it is proposed that the duality is preserved after the limit is taken.
References: 2401.14955 [hep-th]
15/02/24
Title: BPS Wilson loops in mass-deformed ABJM theory
Abstract: ABJM theory, the maximally superconformal gauge theory in three dimensions, stands out for the possibility of exactly computing observables with supersymmetric localization and its relation with string and M-theory. A peculiar property is that it admits an interpretation, even with mass deformations, as a statistical system of N one-dimensional non-interacting fermions. In this talk, I will review the Fermi gas formalism and apply it to derive the exact vev, up to non-perturbative terms, of the 1/6 and 1/2-BPS Wilson loop in ABJM with two mass deformations.
These expressions have several interesting applications. First, looking at the Wilson line as a conformal defect, we exploit the result to derive new defect CFT data and recover the ABJM bremsstrahlung function. Then, we perform strong coupling expansions of the vev and make some predictions for the dual holographic theory in a mass-deformed background.
References: 2401.12288 [hep-th]
25/01/24
Title: Analytic bootstrap for the O(3) magnetic impurity
Abstract: Extended operators such as defects are of fundamental importance in conformal field theories, with applications both in high energy theory and in condensed matter systems at criticality. Recently, analytic bootstrap techniques have been successfully applied to study these objects.
In this talk we will focus on the O(3) magnetic impurity, which at the fixed point is described by a defect conformal field theory.
First, Ward identities arising from the symmetries of the bulk theory and their modification by the presence of the defect are considered. In the case of a free bulk, the inconsistency of these identities implies that in d=3 dimensions there is no non-trivial defect with the assumed symmetries.
Then, in the interacting bulk scenario, the light defect spectrum of the model in the 4-ε expansion is analyzed.
Once the defect spectrum is known, analytic bootstrap techniques are applied to bulk two-point functions to extract an infinite amount of new dCFT data.
References: 2312.05221 [hep-th]
11/01/24
Title: Remarks on BPS Wilson loops in non-conformal N=2 gauge theories and localization
Abstract: Following our recent work (arxiv:2311.17692), we consider 1/2 BPS supersymmetric circular Wilson loops in four-dimensional N = 2 SU(N) supersymmetric Yang-Mills theories with massless matter in a generic representation of the gauge group and a non-vanishing β-function. On the four-sphere S^4, we can employ supersymmetric localization to map these observable into a matrix model, provided that the one-loop determinants are consistently regularized. After constructing the regularized matrix model for these set-ups, we will demonstrate that the predictions for the Wilson loop at order g^4 perfectly match standard perturbative renormalization, based on the evaluation of Feynman diagrams, both on the sphere and also in flat space, despite conformal symmetry being broken at the quantum level. Moreover, I will revisit the difference theory approach, showing that when β-function is non-vanishing this method does not account for the presence of evanescent terms which are activated by the renormalization procedure and contribute to the renormalized observable at order g^6.
References: 2311.17692 [hep-th]