Tensors models exhibit a melonic large $N$ limit, simpler that the planar limit of random matrices but richer that the limit of vector models. In d dimensions, they give rise to a new family of conformal field theories and provide interesting examples of the renormalization group flow from a free theory in the UV to a melonic large $N$ CFT in the IR. I will present some applications of these...
We derive a new classical action for gluodynamics that has no triple gluon vertices. The lowest-order vertex is the four-point MHV vertex. Higher point vertices include the MHV and MHV-bar vertices, which reduce to the corresponding amplitudes in the on-shell limit. In general, any n-leg vertex has 2≤m≤n−2 negative helicity legs. Thus it requires fewer diagrams to calculate amplitudes compared...
4d gauge theories with massless fermions typically have axial U(1) transformations that suffer from the ABJ anomaly. One can modify the theory of interest by adding more fields in a way that restores the axial symmetry, and use it to derive rigorous 't-Hooft anomaly matching conditions. These conditions are not valid for the original theory of interest, but for the modified theory. However,...
We calculate the entropy of an asymptotically Schwarzschild black hole (BH), using an effective field theory of winding modes in type II string theory. In Euclidean signature, the geometry of the BH contains a thermal cycle which shrinks towards the horizon. The light excitations thus include, in addition to the metric and the dilaton, also the winding modes around this cycle. The winding...
I will describe how the geometry of the Higgs branch of 5d superconformal field theories (SCFTs) is transformed under general movement along the extended Coulomb branch. By working directly with the magnetic quiver, I will demonstrate a correspondence between Fayet-Iliopoulos deformations in 3d and 5d mass deformations. This relation provides a new perspective on the interconnectedness of 8...
We consider the order parameter $u=\left<{\rm Tr}\phi^2\right>$ as a function of the running coupling constant $\tau \in \mathbb{H}$ of asymptotically free $\mathcal{N}=2$ QCD with gauge group SU(2) and $N_f\leq 4$ massive hypermultiplets. If the domain for $\tau$ is restricted to an appropriate fundamental domain $\mathcal{F}_{N_f}$, the function $u$ is one-to-one. We demonstrate that these...
Hydrodynamics describes how chaotic QFTs approach thermal equilibrium, by focussing on the dynamics of operators which are long-lived either as a result of conservation laws or of spontaneously broken symmetries. However, real systems typically also involve small explicit breaking of the symmetries which are already spontaneously broken. Generically, the would-be Goldstone modes then acquire...
Large classes of supergravity solutions that appears to be coherent microstates of the D1-D5-P black hole have been found by the Microstate Geometries program. These solutions have a smooth cap at the bottom of a long but finite throat, replacing the black hole's horizon lying at the bottom of an infinitely-long throat.
Because of gravitational blueshift, a small amount of energy as seen from...
The double copy construction in scattering amplitudes hints at a deep connection between Yang-Mills (YM) theory and gravity. It states, roughly speaking, that exchanging the color information by the kinematic information of gluon scattering amplitudes leads to gravity amplitudes. A first principle understanding of this color-kinematic double copy, however, remains elusive. In the interest of...
We explore the dramatic consequences of string-scale supersymmetry breaking. We focus on the USp(32) and U(32) orientifolds of the type IIB and type 0B strings, as well as the SO(16) x SO(16) projection of the exceptional heterotic string, which provide non-tachyonic settings with no moduli directly in ten dimensions. While deceptively innocuous at the level of worldsheet perturbation theory,...
We consider the N=2 SYM theory with gauge group SU(N) and a matter content consisting of one multiplet in the symmetric and one in the anti-symmetric representation of the gauge group. This theory is conformal and it admits a large-N 't Hoof t expansion and a gravity dual given by a particular orientifold of AdS_5 X S^5. We analyze this gauge theory relying on the matrix model provided by...
In this talk I will present how the Generalised geometry framework provides a systematic and simple way to derive consistent truncation of ten and eleven dimension supergravity to any dimension and any amount of supersymmetry.
We introduce a generalized entanglement measure in AdS/CFT measuring entanglement between different fields as well as between spatial degrees of freedom. We explain its definition on the example of two-dimensional holographic conformal field theories and propose a bulk dual in generalization of the Ryu-Takayanagi formula given by the area of codimension two surfaces winding around black hole...
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. Exploiting the notion of MRV limit I will show that, at tree level, all such correlators are completely fixed by...
Matrix models with continuous symmetry are well-studied objects with rich connections to statistics, combinatorics, representation theory and geometry. A natural extension is to consider matrix models with discrete symmetry. Recently, a 13-parameter family of Gaussian 1-matrix models with permutation symmetry was constructed, and the enumeration of permutation invariant observables was...
We use holography to examine the response of interacting quantum fields to the appearance of closed timelike curves in a dynamically evolving background that initially does not contain them. For this purpose, we study a family of two-dimensional spacetimes that model very broad classes of wormhole time machines. The behavior of strongly coupled conformal theories in these spacetimes is then...
We advance two alternative proposals for the island contributions to the entanglement negativity of various pure and mixed state configurations in quantum field theories coupled to semiclassical gravity. The first construction involves the extremization of an algebraic sum of the generalized Renyi entropies of order half. The second proposal involves the extremization of the sum of the...
The island formula – an extremization prescription for generalized entropy – is known to result in a unitary Page curve for the entropy of Hawking radiation. This semi-classical entropy formula has been derived for Jackiw-Teitelboim (JT) gravity coupled to conformal matter using the “replica trick” to evaluate the Euclidean path integral. Alternatively, for eternal Anti-de Sitter black holes,...
One dimensional CFTs are an exceptional laboratory in which we can test novel techniques in order to solve higher dimensional CFTs. They are also relevant from an holographic point of view, as in the case of conformal line defects in 4d N=4 Super Yang-Mills. In this talk, I will present a recursive prescription to compute, up to one loop, 4d N=4 SYM n-point correlation functions realised...
In this talk, I describe recent progress in understanding the background field dynamics of the non-relativistic string theory pioneered by Gomis and Ooguri. Building on earlier developments, I present a non-relativistic supergravity theory and explain how it constrains the dynamics of the background fields. Special attention will be given to the exotic geometric structures that arise in this...
We present a compact formula in Mellin space for the four-point tree-level holographic correlators of chiral primary operators of arbitrary conformal weights in $(2,0)$ supergravity on $AdS_3 \times S^3$, with two operators in tensor multiplet and the other two in gravity multiplet. This is achieved by solving the recursion relation arising from a hidden six-dimensional conformal symmetry. We...
I will discuss G-algebroids — objects generalising Lie and Courant algebroids — and show how to use them to obtain new insights in the areas of exceptional generalised geometry, consistent truncations, and Poisson-Lie U-duality. This is a joint work with M. Bugden, O. Hulík and D. Waldram.
Quantum entanglement and spacetime geometry have a deep connection in holographic systems, and this is most clearly seen through the Ryu-Takayanagi prescription. I describe a new flow-based reformulation of holographic entanglement entropy that is equivalent to the quantum extremal surface (QES) prescription, and so accurate to all orders in bulk quantum corrections. The proposal is inspired...
In this work we start a systematic study of quarter-BPS operators in $\mathcal{N}=4$ SYM with gauge group SU($N$) at large $N$. In particular we consider $\mathcal{O}_{pq}$, operators transforming in the $[q,p,q]$ representation of the SU(4) R-symmetry: when expanded in $\mathcal{N}=2$ supermultiplets, they contain Schur operators making it possible to derive the Ward Identities through the...
The central problem in the numerical conformal bootstrap is finding isolated allowed regions in some subspace of the potential CFT data and to determine the boundaries of these regions. These bounds on the allowed CFT data can be translated into rigorous bounds on physically observable quantities such as the critical exponents controlling the behavior of second order phase...
Infinite towers of massive modes arise for every compactification of higher dimensional theories. Understanding the properties of these Kaluza-Klein towers on non-trivial solutions with an AdS factor has been a longstanding issue with clear holographic interest, as they describe the spectrum of single-trace operators of the dual CFTs at strong coupling and large N. In this talk, I will focus...
Large black holes in anti-de Sitter space have positive specific heat and do not evaporate. In order to mimic the behavior of evaporating black holes, one may couple the system to an external bath. In this paper we explore a rich family of such models, namely ones obtained by coupling two holographic CFTs along a shared interface (ICFTs). We focus on the limit where the bulk solution is...
The Iyer-Wald prescription has been successfully used to derive black hole entropy formulas for higher-derivative, pure gravity theories. However, this does not account for gauge symmetry in the presence of matter gauge fields and, in some cases, the resulting black hole entropy formulas are not Lorentz and gauge invariant. In particular, this is the case for the effective action of the...
Type IIB S-folds of the form $\textrm{AdS}_{4} \times \textrm{S}^1 \times \textrm{S}^5$ have been shown to contain axion-like deformations parameterising flat directions in the 4D scalar potential and corresponding to marginal deformations of the dual S-fold CFT's. In this talk we present a group-theoretical characterisation of such flat deformations and provide a 5D interpretation thereof in...
The main open technical problem to extract reliable low-energy information from string compactifications is understanding the corresponding effective field theories (EFT) beyond tree-level. Perturbative corrections have a direct impact on moduli stabili- sation because the scalar potential vanishes at tree level due to a no-scale property. Even though some corrections have been computed, a...
In standard textbooks of string theory, we learn that due to conformal invariance, the 0, 1 and 2-point functions of bulk vertex operators on genus-0 Riemann surface all vanish. This is another way of saying string theory is only defined on-shell. However, it is sometimes important to have a sensible formulation of string theory in off-shell target space backgrounds (those with non-vanishing...
The infrared physics on the Coulomb branch of 4d $\mathcal{N} = 2$ supersymmetric field theories is encoded in the Seiberg-Witten geometry. We revisit this description for rank one QFTs from the perspective of rational elliptic surfaces, making use of their complete classification in the mathematical literature. This perspective naturally extends to 5d SCFTs with $E_n$ symmetry compactified on...
Integrable deformations of 2-dimensional quantum field theories include the $T\bar T$ and $J \bar T$ deformations. These deformations are well defined in any translationally invariant quantum field theory, including QFTs without Lorentz invariance, such as Warped CFTs. Warped CFTs have been shown to be holographically realized through so-called lower spin gravity. By adapting the deformed...
When performing T-duality on a timelike dimension as well as S-duality, one uncovers a web of type-II string theories which extends to all spacetime signatures and realizes all maximal supersymmetry algebras. In this talk, I will present the N=2 D=4 Supergravity theories one obtains after a Calabi-Yau reduction of the exotic theories. I will present the associated Special Geometry of vector...
The magnetic Weak Gravity Conjecture constrains effective theories with de Sitter critical points by requiring that the Hubble scale is parametrically lower than the WGC cutoff. We argue that in extended supergravity, all dS critical points with light charged gravitini violate this constraint and present a proof of this statement in N=2 supergravity. This excludes all previously known de...
