The large charge expansion

• Susanne Reffert

Room: Aula Magna The large-charge expansion has in the last few years proven to be a powerful tool for analytically accessing strongly-coupled CFTs. When working in a sector of fixed and large global charge, it is often possible to write an EFT for this sector as an expansion controlled by inverse powers of the large charge. I will introduce the large-charge expansion using the O(2) model. Combining the large-charge limit with other simplifying limits allows going beyond the EFT description. At the end of the talk I will give an overview over various recent applications.

Resurgence in CFT2 - Minimal models and beyond?

• Tomas Reis

Room: Aula Magna Following the example of previous work by Benjamin et al. and Kaplan et al., we look at the large charge expansion of the identity block in CFT2. The motivation is clear in AdS/CFT: to look for black holes in the graviton expansion! We start by exhausting the resurgence analysis of four-point function of the (2,1) degenerate fields at finite cross-ratio z. We see that Stokes phenomena in the asymptotic series in large c are controlled by the cross-ratio z, and that the Stokes jumps reveal the other block in the OPE. Time permitting, I'll discuss future directions and on going explorations.

The Numerical Bootstrap of Points and Lines

• Marco Meineri

Room: Aula Magna I will describe how to constrain the spectrum of local operators and boundary conditions, in two dimensions, using the numerical bootstrap. Even for rational theories, it is hard to construct examples of boundary conditions which break all symmetry except Virasoro, let alone classify them. Yet, as always, the OPE data associated with each conformal boundary condition obeys crossing and unitarity. The ensuing constraints can be organized in a semidefinite program, which allows exploration of a multi-dimensional parameter space involving bulk and boundary data.

Constraints from Superconformal Symmetry

• Sophie Mueller

Room: Aula Magna Correlators of half-BPS operators in N = 4 SYM are of massive importance in many research areas, first and foremost AdS/CFT-correspondence and scattering amplitudes. Especially 4- and higher point correlators are of huge interest given, for instance, the wealth of CFT data they contain when utilizing the OPE. Despite their importance, very little is known beyond 4pt functions, primarily due to the lack of a full understanding of the constraints superconformal symmetry places on these object. In this talk, I will present a new method to derive these constraints, the Superconformal Ward Identities, for higher-point correlators of half-BPS operators.

Quantum groups as global symmetries

• Bernardo Zan

Room: Aula Magna Quantum groups are algebras which are known to play a role both in lattice models and in two dimensional CFTs. However, while in the case of lattice models they appear as global symmetries, the situation is more subtle in 2d CFTs. As an example, even if Virasoro minimal models have no quantum group global symmetry, the fusion kernel of Virasoro blocks in these theories contains the 6j symbols of a quantum group. But what does a 2d CFT with a quantum group as a genuine global symmetry look like? I will answer this in the case of the quantum group Uq(sl2), giving both the general picture and studying a specific example arising from the continuum limit of a lattice model. In some cases, this will also give an explanation for the appearance of Uq(sl2) in minimal models.

Modular transformation of c=1 toric conformal block from isomonodromic deformations

• Pavlo Gavrylenko

Room: Aula Magna We will see how isomonodromic tau functions for a torus with one puncture can be expressed in term of c=1 conformal blocks (or \mathcal{N}=2* gauge theory partition functions). Then we will study monodromy dependence of these tau functions, find their behavior under the modular transformation \tau\to-1/\tau, and then use this knowledge to find an explicit formula for the fusion kernel for c=1 conformal block. The talk will be based on a joint work with Fabrizio Del Monte and Harini Desiraju.

Locality and Operator Algebras in Quantum Gravity

• Alex Belin

Room: Aula Magna

Entanglement spectra from holography

• Stefano Baiguera

Room: Aula Magna We investigate the degeneracy in the distribution of the entanglement spectrum for holographic conformal field theories in general dimensions. The input is given by the Renyi entropies for a spherical (or planar) entangling surface. We show that the energy and entropy of the system satisfy a universal generalization of the Cardy formula valid in generic dimensions. We then move to the case when a global charge is present in the system, focusing on the supersymmetric case obtained via a fine-tuning of the charge. In such case, we derive another universal formula. Finally, we show that small shape deformations of the entangling surface do not spoil the previous results.

Double Copy Supertranslations

• Dario Francia

Room: Aula Magna In the framework of the convolutional double copy, we investigate the asymptotic symmetries of the gravitational multiplet stemming from the residual symmetries of its single-copy constituents at null infinity. We show that the asymptotic symmetries of Maxwell fields in D = 4 imply “double-copy supertranslations”, i.e. BMS supertranslations and two-form asymptotic symmetries, together with the existence of infinitely many conserved charges involving the double-copy scalar.

An Algebraic Perspective on Carrollian Holography

• Michel Pannier

Room: Aula Magna Holographic dualities provide a promising framework to approach open questions of quantum gravity, information theory and strongly coupled systems; yet, a complete realisation of Holography beyond the realm of AdS/CFT is still to be achieved. This talk is motivated by an attempt to construct holographic dualities involving asymptotically flat spacetimes, in particular one that intends to resemble the set-up of AdS/CFT and is dubbed "Carrollian Holography". I will discuss some of the obstacles within this approach from the perspective of the bulk spacetime and motivate how algebraic methods may provide a robust, symmetry-based way to approach the construction of holographic toy models. As a concrete example, I will focus on the role played by coherent states and their role in the description of holographic probes.

Massive Gravity in the Worldline Formalism

• Filippo Fecit

Room: Aula Magna Despite the considerable success of General Relativity, the search for alternatives has been an ongoing challenge since its formulation to address some of the most crucial open questions in physics, such as the cosmological constant problem and the origin of the late-time acceleration of the universe. An intriguing modification suggests that gravity could be propagated by a massive spin 2 particle: a massive graviton.
In this talk, I will present a novel discussion from a worldline perspective, employing the first-quantized models known as O(N) spinning particles. Specifically, our focus will be on the massive N=4 spinning particle. First, I will show that BRST quantization allows for the correct reproduction of the Fierz-Pauli theory on Minkowski. The extension to curved spacetime is trickier, and nilpotency of the BRST charge seems to require a Ricci-flat spacetime as the only consistent background. Once the BRST system is realized, it is possible to construct the worldline path integral on the circle, providing a worldline representation of the one-loop effective action of Linearized Massive Gravity. If time permits, I will discuss the calculation of the Seeley-DeWitt coefficients, including the a_3(D) coefficient previously not known in the literature.

Gauge Theory meets Cosmology

• Giuseppe Dibitetto

Room: Aula Magna We reconsider linear perturbations around general Friedmann - Lemaitre - Robertson - Walker (FLRW) cosmological backgrounds. Exploiting gauge freedom involving only time reparametrizations, we write down classical background solutions analytically, for an arbitrary number of fluid components. We then show that the time evolution of scalar and tensor adiabatic perturbations are governed by Schr¨odinger-like differential equations of generalized Heun type. After recovering known analytic results for a single-component fluid, we discuss more general situations with two and three different fluid components, with special attention to the combination of radiation, matter and vacuum energy, which is supposed to describe the ΛCDM model. The evolution of linear perturbations of a flat ΛCDM universe is described by a two-transient model, where the transitions from radiation to matter and matter to vacuum energy are governed by a Heun equation and a Hypergeometric equation, respectively. We discuss an analytic approach to the study of the general case, involving generalized Heun equations, that makes use of (quantum) Seiberg-Witten curves for N = 2 supersymmetric gauge theories and has proven to be very effective in the analysis of Black-Hole, fuzzball and ECO perturbations.

Type IIB S-folds: solutions and consistent truncations

• Colin Sterckx

Room: Aula Magna We will report on new and old solutions of type IIB supergravity on M_4 x S^1 x S^5 with an SL(2, Z) monodromy along the S^1. These solutions are called type IIB S-folds. They are built using a consistent truncation of type IIB SUGRA to a 4D maximal gauged supergravity. This 4d supergravity admits a rich landscape of solutions: supersymmetric and non-supersymmetric AdS_4 vacua, universal black-holes, and even a peculiar family of scale separated solution with M_4 = AdS_2 x H^2. To build on these results we will also show how to consistently embed the pure N=4 SO(4)_R gauged supergravity as an S-fold. This opens the possibility to study many more BH solutions and further test the AdS/CFT conjecture in the context of S-folds.

Thermodynamics of near-extreme rotating black holes

• Chiara Toldo

Room: Aula Magna In this talk I will review recent results concerning the microscopics and the thermodynamics of fast spinning black holes in asymptotically flat and Anti-de Sitter space. I will first describe how recently developed techniques allow to compute the quantum corrections to the entropy of near-extremal Kerr black holes. I will show that the quantum-corrected near-extremal entropy exhibits 3/2logT behavior characteristic of the Schwarzian model, and predicts a lifting of the ground state degeneracy for the extremal Kerr black hole. In addition, I will show the computation for the density of states for fast spinning black holes in AdS4, which admit a supersymmetric limit, and comment on the spectrum of near-BPS states and on the interpretation in terms of the dual 3d field theory.

Hagedorn temperature in holography: world-sheet and effective approaches

• Tommaso Canneti

Room: Aula Magna I will provide general advances on the Hagedorn temperature of planar, strongly coupled confining gauge theories holographically dual to type II superstring models on curved backgrounds with Ramond-Ramond and Kalb-Ramond fluxes and non-trivial dilaton. The final result will be determined up to a certain order in an expansion in the string length and relies on two complementary approaches: the semiclassical quantization of string configurations winding around the compact Euclidean time direction and the perturbative solution to the equations of motion for the thermal scalar field corresponding to the lightest mode of the winding string.

Species Cosmology

• Marco Scalisi

Room: Aula Magna Towers species can significantly affect the properties of gravitational effective field theories. They naturally appear in string theory, and one of their universal effects is a renormalization of the scale at which gravity becomes strongly coupled. In this talk, we will discuss some of the implications for cosmology arising from the presence of a large number of species. A major focus will be on cosmic inflation and its observational signatures in the cosmic microwave background. We will also discuss some of the implications for Starobinsky inflation.

Brane solutions in non-supersymmetric strings

• Salvatore Raucci

Room: Aula Magna Can low-energy gravity capture the backreaction of extended sources without the protection of supersymmetry? In this talk, I address this question in the context of non-supersymmetric string theories. Branes are expected from the worldsheet analysis, but their spacetime solutions are heavily affected by the absence of supersymmetry. A ubiquitous feature is the presence of finite-distance singularities, although all cases predicted by the worldsheet yield normalizable solutions even with singular boundaries.

New tachyon-free non-SUSY heterotic vacua in six and four dimensions

• Giorgio Leone

Room: Aula Magna It is widely known that non-supersymmetric heterotic theories are plagued by instabilities ascribed to the presence of tachyons or dilaton tadpoles. Moreover, geometric compactifications admit the presence of moduli, which may be used to deform the model, once non-trivial Wilson lines are turned on. For instance, in nine dimensions, tachyon-free theories can be connected to tachyonic ones, thus jeopardising the tree-level stability of the vacuum. In this picture, truly non-supersymmetric tachyon-free heterotic models in lower dimensions are hard to find and one should require more sophisticated non-geometric constructions, such as asymmetric or quasi-crystalline orbifolds, which only exist on special points of the moduli space and cannot be further deformed. In this presentation, I will discuss specific asymmetric orbifolds in six and four dimensions, which do not admit deformation moduli and provide truly non-supersymmetric tree-level tachyon-free vacua with reduced rank.

Review on Generalized Symmetries

• Francesco Benini

Room: Aula Magna I will review foundations and recent progresses in generalized symmetries. In particular I will discuss the development of the structure and mathematical formulation of generalized symmetries and their anomalies, as well as some applications to concrete examples and physical problems.

Decomposition and (-1)-form symmetries in the SymTFT

• Ling Lin

Room: Aula Magna A d-dimensional QFT with a (d-1)-form global symmetry decomposes into a disjoint union of different QFTs related by a (-1)-form symmetry. In this talk I will discuss these symmetries and the associated decomposition in the framework of the Symmetry TFT, using various examples such as 4d Yang—Mills or 3d ABJ(M) theories.

Mirror dualities with four supercharges

• Riccardo Comi

Room: Aula Magna Mirror duality relates pairs of 3d N=4 theories that share the same Infra-Red fixed point. At first, it was understood that mirror duality is induced from S-duality acting on the brane setups that engineers the 3d N=4 theories. I will discuss a different perspective on the topic, showing that 3d N=4 mirror dualities can be proved purely in field theory using the dualization algorithm. I will then show how to extend this approach to theories with less amount of SUSY, namely 3d N=2 theories, showing a proposal for an exact mirror dual of the 3d N=2 SQCD. I will also show how this result provides more insight on brane setups with four supercharges.

ABJM theory and defect RG flows

• Marcia Tenser

Room: Aula Magna I will talk about defect renormalization group flows recently found in ABJM theory. In such a setting, we find RG flow trajectories that may or may not preserve some subset of the original N=6 supersymmetry. The beta-functions have a large spectrum of fixed points representing superconformal defects that provide a rich arena to study quantum effects in 2+1 dimensional theories. In this context we study universal information about ABJM, such as the Bremsstrahlung function, and the effect of framing on the defect vacuum expectation value.

Fermion-Monopole Scattering in a Chiral Gauge Theory

• Bruno Bucciotti

Room: Aula Magna The scattering of low-energy charged massless fermions on magnetic monopoles in the s-wave presents a long-standing final state puzzle: it seems to be generally impossible to construct an outgoing state conserving all global and gauge charges. Indeed, bosonizing the low-energy EFT, one is seemingly led to particles of fractional charge. In this talk I describe this problem starting from a UV complete chiral gauge theory, and descending to the EFT. This step allows us to discuss and exclude some existing proposed solutions to the puzzle. We then find that a correct bosonization of the theory does give a meaningful outgoing state, at the price of introducing a topological operator similar to one suggested in arxiv:2306.07318.

One-loop integrable S-matrices from tree-level

• Davide Polvara

Room: Aula Magna Integrable quantum field theories in 1+1 dimensions play a central role in many areas of physics.  They provide examples of exactly solvable models, whose S-matrices can be conjectured through the so-called S-matrix bootstrap program. While this axiomatic program allowed in the past decades for the determination of the S-matrices of several integrable theories, there is now growing evidence that many S-matrices are hardly obtained through the bootstrap, as is the case for many non-linear sigma models defined on the worldsheet of superstrings. In this talk I will propose an alternative way to construct the S-matrices of 1+1 dimensional integrable theories which relies on standard perturbation theory; starting from the assumption that the theory is integrable at the tree level I will show how to write sums of one-loop diagrams in terms of tree amplitudes and I will derive in this way a universal formula for the one-loop two-to-two S-matrices in terms of tree S-matrices. I will show how this method works for integrable bosonic Lagrangians with polynomial interactions.