Holographic QFTs on AdS_d, wormholes and holographic interfaces

• Elias Kiritsis (Crete U.)

We consider three related topics: a) holographic quantum field theories on AdS spaces; b) Holographic interfaces of flat space QFTs; c) Wormholes connecting generically different QFTs. We investigate how the related classical solutions explore the space of QFTs and we construct the general solutions that interpolate between the same or different CFTs with arbitrary couplings. The solution space contains many exotic RG flow solutions that realize unusual asymptotics, as boundaries of different regions in the space of solutions. Unusual limits also appear where the number of boundaries changes. We also investigate confining holographic theories on AdS.

Equivariant localization for AdS/CFT

• Pietro Benetti Genolini (University of Geneva)

Equivariant localization may be applied to AdS/CFT to compute various BPS observables in gravity without solving the supergravity equations. The key ingredient is that supersymmetric solutions with an R-symmetry are equipped with a set of equivariantly closed forms. These may in turn be used to impose flux quantization and compute observables for supergravity solutions, using only topological information and the fixed point formula.

How to Build a Black Hole out of Instantons

• Rishi Mouland (DAMTP, University of Cambridge)

AdS/CFT has given a us a smorgasbord of holographic CFTs, from which we can try to learn about quantum gravity. Yet, access to dynamical observables is usually severely limited. We are thus motivated to study holographic models of quantum mechanics, which offer new routes to both analytic and numerical study. I will explain how quantum gravity emerges from the quantum mechanics of Yang-Mills instantons, and how we can construct black holes in the bulk dual. I will provide a precise microscopic derivation of the entropy of supersymmetric black holes in this model.

Type IIB gauged supergravities and M2-brane twisted torus bundles

• Camilo las Heras (Instituto de Física Teórica UAM-CSIC)

In this talk, we propose that the M2-brane with fluxes and monodromy is able to reproduce at low energies the type IIB gauged supergravities in 9d. The worldvolume description of these M2-branes with nonvanishing winding on a torus is known. They have good quantum properties, such as the discreteness of the supersymmetric spectrum. Their global description is given in terms of twisted torus bundles with monodromy contained in $SL(2,Z)$. We found a relation between the equivalence classes of twisted torus bundles and the gauging of the symmetry on type IIB supergravities in 9d. We briefly mentioned the relation of this quantum description to other ones given previously in terms of F-theory.

Integrable deformations and supergravity backgrounds

• Georgios Itsios (Humboldt University)

In this talk, I will discuss the construction of two supersymmetric solutions of type-II supergravity based on the λ-deformed σ-models for SL(2,R) and SU(2). In the absence of deformation, they describe near-horizon limits of NS1 and NS5 brane intersections and both are 1/2-supersymmetric. When the deformation is turned on, supersymmetry breaks by half and both backgrounds preserve 8 supercharges.

Spin-Statistics for Black Hole Microstates

• Gustavo Turiaci (University of Washington)

The gravitational path integral can be used to compute the number of black hole states for a given energy, or the free energy in a fixed temperature ensemble. We explain how to use this approach to estimate the number of bosonic and fermionic black hole microstates. We do this by comparing the partition function with and without the insertion of (-1)^F. We study this problem for black holes in asymptotically flat space and in AdS, putting constraints on the high energy spectrum of holographic CFTs (not necessarily supersymmetric). Finally, we analyze wormhole contributions to related quantities.

Tearing down spacetime with quantum disentanglement

• Roberto Emparan (ICREA + U Barcelona)

A longstanding enigma within AdS/CFT concerns the entanglement entropy of holographic quantum fields in Rindler space. The vacuum of a quantum field in Minkowski spacetime can be viewed as an entangled thermofield double of two Rindler wedges at a temperature $T=1/2\pi$. We can gradually disentangle the state by lowering this temperature, and the entanglement entropy should vanish in the limit $T\to 0$ to the Boulware vacuum. However, holography yields a non-zero entanglement entropy at arbitrarily low $T$, since the bridge in the bulk between the two wedges retains a finite width. We show how this is resolved by bulk quantum effects of the same kind that affect the entropy of near-extremal black holes. The large quantum fluctuations in the geometry of the bridge bring down to zero the density of entangled states in the Boulware vacuum. We also construct unentangled Boulware states in de Sitter space.

Gong Show I

• Ana Climent
• Carmen las Heras
• David Mayo
• Evangelos Afxonidis
• Giacomo Giorgi
• João Vilas Boas
• Juan Suárez

List of speakers Gong Show I: Ana Climent - https://indi.to/btVc2 Carmen Gómez-Fayrén de las Heras - https://indi.to/87KKq David Travieso Mayo - https://indi.to/fqdcw Evangelos Afxonidis - https://indi.to/jx5DT Giacomo Giorgi - https://indi.to/dC8W9 João Vilas Boas - https://indi.to/7XjL2 Juan Santos Suárez - https://indi.to/3fvZ6

Outreach

• Jose Edelstein (Universidade Santiago Compostela)

Approximate CFTs and Random Tensor Models

• Alex Belin (Milan Bicocca U)

Over the past few years, the importance of chaos in the physics of quantum black holes has become clear. This is particularly well understood in two-dimensional gravity, where the boundary system is quantum mechanics. Quantum chaos is well understood in quantum mechanics, going back several decades to the work of Wigner, in terms of random matrix universality: the statistical spectral correlations of a chaotic hamiltonian are indistinguishable from those of a random matrix drawn from the appropriate ensemble. Quantum chaos is much less understood in quantum (and conformal) field theories, which appear in top-down realizations of AdS/CFT. What is the right ensemble of theories to draw from in the case of field theories, similar to the random matrix ensembles of Wigner? In this talk, I will review progress on this front, and explain how to incorporate the many CFT constraints into a framework of ensemble of CFTs.

A Bootstrap bridge between gravity and QCD

• Andrea Guerrieri (Perimeter Institute and Università di Padova)

The numerical S-matrix Bootstrap aims at establishing non-perturbative universal bounds on physical observables that can be extracted from scattering amplitudes in any dimension. In this talk, I will focus on dimensions greater or equal to four, focusing on two main topics: no-go theorems for supersymmetric quantum gravity, and Bootstrapping the QCD spectrum using physical glueballs, and pion scattering. These results are obtained by going beyond the simple positivity of scattering amplitude, with the introduction of the non-linear unitarity inequalities. During the discussion, I will describe the Bootstrap methodology and the numerical challenges we face when tackling these problems. I will conclude with a list of possible future directions that I believe are interesting for the development of the field.

Disconnected gauge groups in the infrared

• Guillermo Arias Tamargo (Imperial College London)

Gauging a discrete 0-form symmetry of a QFT is a procedure that changes the global form of the gauge group but not its perturbative dynamics. In this talk, we will discuss the Seiberg-Witten solution of theories resulting from the gauging of charge conjugation in 4d N = 2 SQCD with SU(N) gauge group. The basic idea is to identify the Z_2 action at the level of the SW curve and perform the quotient, and it should also be applicable to non-lagrangian theories. We study dynamical aspects of these theories such as their moduli space singularities and the corresponding physics; in particular, we explore the complex structure singularity arising from the quotient procedure. Time permitting, I'll also discuss some implications of our work in regards to three problems: the geometric classification of 4d SCFTs, the study of non-invertible symmetries from the SW geometry, and the String Theory engineering of theories with disconnected gauge groups.

Two loop five point integrals: light, heavy and large spin correlators.

• Carlos Bercini (DESY)

We evaluated all conformal integrals appearing in the two-loop five-point functions of protected operators in $\mathcal{N}=4$ Super Yang-Mills in two kinematical regimes. From the correlation function of the lightest operators of the theory we were able to extract structure constants of one and two spinning operators for small values of polarizations and arbitrary spin. We conjectured a universal all loop behavior of these structure constants and commented on the subtleties of analytically continuing it from finite to large spin. We also consider correlation functions of heavier operators that get factorized in the so-called decagon. We fixed this object in general kinematics at two-loops and studied its physical properties under OPE and null limits

Conformal bounds from entanglement

• Pablo Bueno (Universidad de Barcelona)

The entanglement entropy of an arbitrary spacetime region $A$ in a three-dimensional conformal field theory (CFT) contains a constant universal coefficient, $F(A)$. For general theories, the value of $F(A)$ is minimized when $A$ is a round disk, $F_0$, and in that case it coincides with the Euclidean free energy on the sphere. I will present a new conjecture stating that for general CFTs, the quantity $F(A)/F_0$ is bounded above by the free scalar field result and below by the Maxwell field one. I will provide strong evidence in favor of this claim and argue that an analogous conjecture in the four-dimensional case is equivalent to the Hofman-Maldacena bounds. In three dimensions, our conjecture gives rise to similar bounds on the quotients of various constants characterizing the CFT. In particular, it implies that the quotient of the stress-tensor two-point function coefficient and the sphere free energy satisfies $C_T/F_0 ≤ 3/(4\pi \log2−6\zeta[3]) \simeq 0.14887$ for general CFTs. I will show that the bound is satisfied by free scalars and fermions, general $O(N)$ and Gross-Neveu models, holographic theories, $N=2$ Wess-Zumino models and general ABJM theories.

One-Loop String Amplitudes Revisited

• Lorenz Eberhardt (Amsterdam U.)

We reconsider one-loop amplitudes of gauge bosons and gravitons in both type I and II string theory. They are given by explicit integrals over the moduli space of surfaces and are some of the richest and most interesting quantities of string theory. The integrals are quite hard to evaluate directly, which makes it difficult to extract physics from the integral expressions. We apply a number of techniques such as contour deformations, Rademacher expansion and saddle point approximation to understand the amplitude. We are in particular able to evaluate the type I amplitude numerically and check long-standing conjectures about their behavior at high energies, where they differ drastically from QFT amplitudes. The talk is based on work with S. Mizera, as well as on-going work with S. Mizera and P. Banerjee.

An emergent entanglement wedge from matrix quantum mechanics

• Jackson Fliss (University of Cambridge)

The geometrization of entanglement and the formation of an entanglement wedge is a profound feature of quantum gravity: in spite of bulk diffeomorphism invariance, microscopic degrees of freedom are encoded in bulk regions of minimal area. I will explain a simple model of NxN matrix quantum mechanics that displays this feature. The model has a semi-classical solution describing a non-commutative, or fuzzy, sphere upon which a U(N) gauge symmetry acts, at large N, as area-preserving diffeomorphisms. Considering the gauge-invariant question “what is the entanglement entropy of the state reduced to M units of area?” I will give evidence of a transition at strong coupling whereby the answer to this question is dominated by a saddle-point where all the entangled degrees of freedom coalesce into a cap region of minimal perimeter on the fuzzy sphere. The entanglement entropy is given by the perimeter of this emergent entanglement wedge.

Gong Show II

• Unai Sárraga
• Matilda Delgado
• Rathindra Das
• Rafael CARMONA
• Martí Mimo
• MATTEO Zatti
• Romina Ballesteros
• Quim Llorens

List of speakers Gong show II Martí Berenguer Mimó - https://indi.to/BTPXT Matilda Delgado - https://indi.to/tHJTs Matteo Zatti - https://indi.to/9wQKS Quim Llorens Giralt - https://indi.to/gHTP2 Rafael Carrasco Carmona - https://indi.to/gvq2N Rathindra Nath Das - https://indi.to/mNwNZ Romina Ballesteros - https://indi.to/mdVpm Unai Sárraga - https://indi.to/pPNXg

Conference Dinner Conference dinner at Nogueira restaurant Nogueiras´s Porto, R. de Ceuta 23, 4050-191 Porto

Quantum Curves and Black holes

• Alba Grassi (Geneva University)

In recent decades, the field of physical mathematics has undergone remarkable developments, leading to numerous powerful results. Among them is the discovery of connections between quantum spectral problems on the one hand, and supersymmetric gauge theory or topological string theory on the other. In this talk I will review some aspects of this correspondence and discuss an intriguing new connection between such framework and black holes.

Carroll black holes

• Daniel Grumiller (TU Wien)

Despite the absence of a lightcone structure, some solutions of Carroll gravity show black hole-like behaviour. We define Carroll black holes as solutions of Carroll gravity that exhibit Carroll thermal properties and have a Carroll extremal surface. Examples include Carroll versions of Schwarzschild, Reissner-Nordström, BTZ, JT, and Witten black holes.

Universal construction of black hole microstates

• Alejandro Vilar López (Université Libre de Bruxelles (ULB))

It has been recently proposed that it is possible to build microstates for two-sided Schwarzschild black holes by inserting backreacting shells of matter trapped behind the horizon. This procedure seemingly produces an arbitrarily large number of different microstates, creating a tension with the Bekenstein-Hawking entropy calculation which is solved by showing that the states are not orthogonal due to non-perturbative gravitational effects in the form of Euclidean wormholes. In this talk, I will argue that this construction is completely universal, and it can be extended to charged and rotating black holes, including the extremal and near-extremal solutions. Furthermore, the set-up allows to account for all quantum corrections found in previous computations of the Gibbons-Hawking partition function.

Adventures in 5d Higher-derivative Supergravity

• Marina David (KU Leuven)

Higher-derivative corrections in the AdS/CFT correspondence allow us to capture finer details of the dual CFT and to explore the holographic dictionary beyond the infinite N and coupling limits. Following an EFT approach, I will discuss extremal AdS black hole solutions in five dimensional supergravity with higher-derivative corrections. I will first provide a general analysis of near-horizon geometries of rotating extremal black holes and I will show how to obtain the charges and chemical potentials from them. I will discuss the near-horizon solutions of the two-derivative theory, which we write using a novel parametrization, and next I will show how to compute the higher-derivative corrections of those solutions. The charges and thermodynamic properties of the black hole will then be discussed, along with the ambiguities in the definition of some of these quantities. The charges and potentials turn out to satisfy a “near-horizon version” of the first law of thermodynamics whose interpretation I will make clear. In the supersymmetric case, the results will be shown to match the field theory prediction as well as previous results obtained from the on-shell action.

Low d singularities

• Marija Tomasevic (University of Amsterdam)

We study black holes in two and three dimensions that have spacelike curvature singularities behind horizons. The 2D solutions are obtained by dimensionally reducing certain 3D black holes, known as quantum BTZ solutions. Furthermore, we identify the corresponding dilaton potential and show how it can arise from a higher-dimensional theory. Finally, we show that the rotating BTZ black hole develops a singular inner horizon once quantum effects are properly accounted for, thereby solidifying strong cosmic censorship for all known cases.

Bounds on effective theories of gravity

• Julio Parra Martinez (British Columbia U.)

Modifications of Einstein’s gravity can be systematically analyzed using the framework of effective field theory. In this setup, new physics is captured in a set of higher-dimension operators whose coefficients must be measured experimentally, or matched from a UV completion such as string theory. It has been known for some time that basic principles such as unitarity and causality impose constraints on the allowed values of such coefficients, but a systematic framework to explore these constraints has only recently emerged. In this talk I will review how developments in scattering amplitudes and the conformal bootstrap allowed us to compute sharp numerical bounds on these coefficients. Such bounds imply that gravitational interactions must shut off uniformly in the limit of vanishing Newton’s constant, and prove the scaling with the cutoff expected from dimensional analysis. In addition they demonstrate that graviton scattering must remain weakly coupled at the scale where new higher-spin particles appear. Time permitting, I will comment on possible future applications of this set of ideas.

Scale-separation and massive type-IIA orientifolds

• MATTEO MORITTU (Universidad de Oviedo)

I will discuss supersymmetric AdS_3 flux vacua of massive type-IIA supergravity on G2 orientifolds, focusing on (non) scale separated configurations at large volume and weak-.coupling, also highly anisotropic. I wil show, for instance, that depending on the F_4 flux the 7-dimensional compact space can either have six small and one large dimension so that the "external" space is scale-separated and effectively 4-dimensional, or all seven compact dimensions small and parametrically scale-separated from the three external ones. I will also discuss the realization of the Swampland Distance Conjecture within such setups via the inclusion of appropriate D4-branes.

Integrability in non-relativistic string theory

• JUAN Nieto (Universität Hamburg)

Integrability has played a huge role in understanding string theory in AdS5xS5. This has motivated people to explore if integrability techniques can be applied to more general backgrounds. One of these cases is the non-relativistic limit of AdS5xS5. In this talk, I will report on recent progress in understanding classical integrable structures present in non-relativistic string theory propagating in string Newton-Cartan AdS5xS5. In particular, I will discuss classical solutions, the coset construction of the action, the Lax connection and the classical spectral curve.

The Curious Case of de Sitter vacua

• Bruno Bento (IFT UAM-CSIC)

Surprisingly (or not) de Sitter vacua has proved hard to find in the string Landscape. Although some proposals have been made over the years, the details of the necessary ingredients and questions of control have been raised as potential loopholes in these constructions. The difficulty of realising a clean and beyond-any-doubt de Sitter vacuum has lead to its own Swampland conjecture, which -- instead of killing the hope to find one -- has intensified the search more than ever. In this talk I will give a brief overview of the curious case of de Sitter vacua as it stands and present an attempt to construct one using Casimir energies and flat compact manifolds.