In chaotic quantum systems the spectral form factor exhibits a universal linear ramp and plateau structure with superimposed erratic oscillations. The mean signal and the statistics of the noise can be probed by the moments of the spectral form factor, also known as higher-point spectral form factors. We identify saddle points in the SYK model that describe the moments during the ramp region. Perturbative corrections around the saddle point indicate that SYK mimics random matrix statistics for the low order moments, while large deviations for the high order moments arise from fluctuations near the edge of the spectrum. The leading correction scales inversely with the number of random parameters in the SYK Hamiltonian and is amplified in a sparsified version of the SYK model, which we study numerically, even in regimes where a linear ramp persists. Finally, we study the $\textit{q}$ = 2 SYK model, whose spectral form factor exhibits an exponential ramp with increased noise. These findings reveal how deviations from random matrix universality arise in disordered systems and motivate their interpretation from a bulk gravitational perspective.

Italy

Andrea Legramandi

United Kingdom

Neil Talwar

The moments of the spectral form factor in SYK

We derive necessary and sufficient conditions for warped AdS2 solutions of Type II supergravity to preserve   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 1 supersymmetry, in terms of bispinors. Such solutions generically support an SU(3)-structure on their internal manifold M8, which can experience an enhancement to a G2-structure. We perform an SU(3)-structure torsion classes analysis and express the fluxes and other physical fields in terms of these, in general. We use our results to derive two new classes of AdS2 solutions. In (massive) Type IIA supergravity we derive an   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 1 supersymmetric class for which M8 decomposes as a weak G2-manifold foliated over an interval and which is locally defined in terms of a degree three polynomial. In Type IIB supergravity we find a class of AdS2 × S2 × CY2 × Σ2 solutions preserving small   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 4 supersymmetry, governed by a harmonic function on Σ2 and partial differential equations reminiscent of D3-D7-brane configurations.

Spain

Niall Macpherson

France

Achilleas Passias

G-structures for black hole near-horizon geometries

We construct a holographic map that takes the semi-classical state of an evaporating black hole and its Hawking radiation to a microscopic model that reflects the scrambling dynamics of the black hole. The microscopic model is given by a nested sequence of random unitaries, each one implementing a scrambling time step of the black hole evolution. Differently from other models, energy conservation and the thermal nature of the Hawking radiation are taken into account. We show that the QES formula follows for the entropy of multiple subsets of the radiation and black hole. We further show that a version of entanglement wedge reconstruction can be proved by computing suitable trace norms and quantum fidelities involving the action of a unitary on a subset of Hawking partners. If the Hawking partner is in an island, its unitary can be reconstructed by a unitary on the radiation. We also adopt a similar setup and analyse reconstruction of unitaries acting on an infalling system.

Zsolt Gyongyosi

Timothy Hollowood

S. Kumar

The holographic map of an evaporating black hole

We study five-dimensional <math><mi>N</mi><mo>=</mo><mn>1</mn></math> Superconformal Field Theories of the linear quiver type. These are deformed by a relevant operator, corresponding to a homogeneous mass term for certain matter fields. The free energy is calculated at arbitrary values of the mass parameter. After a careful regularisation procedure, the result can be put in correspondence with a calculation in the supergravity dual background. The F-theorem is verified for these flows, both in field theory and in supergravity. This letter presents some of the results in the companion paper [1].

Japan

Mohammad Akhond

Carlos Nunez

China

Leonardo Santilli

Lucas Schepers

Massive flows in AdS /cft

We consider the issue of information recovery for an object carrying energy and entropy into a black hole using the generalized entropy formalism, in the context of JT gravity where the backreaction problem can be solved exactly. We verify the main aspects of the Hayden-Preskill scenario but with some refinements. We show that the information is encoded in the Hawking radiation in a redundant way, as expected for a quantum error correcting code. We show how quantum extremal surfaces associated to information recovery have the form of a python’s lunch and thereby show that the complexity of decoding is exponential in a combination of the entropy shift of the black hole and the entropy of the object. We also show that an infalling observer must have a smooth experience at the horizon and we calculate their endurance proper time inside the black hole before they are radiated out.

Black hole information recovery in JT gravity

We consider the effect of grey-body factors on the entanglement island prescription for computing the entropy of an arbitrary subset of the Hawking radiation of an evaporating black hole. When there is a non-trivial grey-body factor, the modes reflected back into the black hole affect the position of the quantum extremal surfaces at a subleading level with respect to the scrambling time. The grey-body factor allows us to analyse the role of irreversibility in the evaporation. In particular, we show that irreversibility allows multiple saddles to dominate the entropy, rather than just two as expected on the basis of Page’s theorem. We show that these multiple saddles can be derived from a generalization of Page’s theorem that involves a nested temporal sequence of unitary averages. We then consider how irreversibility affects the monogamy entanglement problem.

Grey-body factors, irreversibility and multiple island saddles

We present three infinite families of supersymmetric Type IIB backgrounds with AdS4, AdS3 and AdS2 factors, dual to SCFTs in 3, 2 and 1 space-time dimensions respectively. These field theories emerge at low energies, after a twisted compactification of a family of five dimensional   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 1 SCFTs on hyperbolic spaces. The holographic flows across dimensions are explicitly computed. We also discuss a family of SUSY breaking backgrounds, dual to a QCD-like quiver with massive (bi)fundamental matter. Some field theoretical observables are computed for these theories at the fixed points and along the flow.

Holographic description of SCFT5 compactifications

We consider entanglement entropies of finite spatial intervals in Minkowski radiation baths coupled to the eternal black hole in JT gravity, and the related problem involving free fermion BCFT in the thermofield double state. We show that the non-monotonic entropy evolution in the black hole problem precisely matches that of the free fermion theory in a high temperature limit, and the results have the form expected for CFTs with quasiparticle description. Both exhibit rich behaviour that involves at intermediate times, an entropy saddle with an island in the former case, and in the latter a special class of disconnected OPE channels. The quantum extremal surfaces start inside the horizon, but can emerge from and plunge back inside as time evolves, accompanied by a characteristic dip in the entropy also seen in the free fermion BCFT. Finally an entropy equilibrium is reached with a no-island saddle.

Ephemeral islands, plunging quantum extremal surfaces and BCFT channels

In this paper we discuss an infinite class of AdS$_{6}$ backgrounds in Type IIB supergravity dual to five dimensional SCFTs whose low energy description is in terms of linear quiver theories. The quantisation of the Page charges imposes that each solution is determined once a convex, piece-wise linear function is specified. In the dual field theory, we interpret this function as encoding the ranks of colour and flavour groups in the associated quiver. We check our proposal with several examples and provide general expressions for the holographic central charge and the Wilson loop VEV. Some solutions outside this general class, with less clear quiver interpretation, are also discussed.

Electrostatic description of five-dimensional SCFTs

We present the holographic dual for the strongly coupled, low energy dynamics of balanced   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 4 field theories in (2 + 1) dimensions. The infinite family of Type IIB backgrounds with AdS4 × S 2 × S 2 factors is described in terms of a Laplace problem with suitable boundary conditions. The system describes an array of D3, NS5 and D5 branes. We study various aspects of these Hanany-Witten set-ups (number of branes, linking numbers, dimension of the Higgs and Coulomb branches) and encode them in holographic calculations. A generic expression for the Free Energy/Holographic Central Charge is derived. These quantities are then calculated explicitly in various general examples. We also discuss how Mirror Symmetry is encoded in our Type IIB backgrounds. The connection with previous results in the bibliography is made.