We illustrate scenarios in which Hawking radiation collected in finite regions of a reservoir provides temporary access to the interior of black holes through transient entanglement "islands". Whether these islands appear and the amount of time for which they dominate - sometimes giving way to a thermalization transition - is controlled by the amount of radiation we probe. In the first scenario, two reservoirs are coupled to an eternal black hole. The second scenario involves two holographic quantum gravitating systems at different temperatures interacting through a Rindler-like reservoir, which acts as a heat engine maintaining thermal equilibrium. The latter situation, which has an intricate phase structure, describes two eternal black holes radiating into each other through a shared reservoir.

I discuss N = 4 SYM theories with su(N) gauge algebra, classified by the quotient discrete groups and line (and surface) operators, via the holographic dual description. The one-form symmetries and the line operator spectrum of the different theories are realized by the different boundary conditions on the NSNS and RR 2-forms in type IIB string theory. The topics include the holographic realization of the SL(2,Z) duality orbit, the mixed ’t Hooft anomaly involving the one-form and CP symmetries, and the interfaces between vacua with different values of the theta parameter. This talk is based on the work-in-progress in collaboration with Oren Bergman.

We consider the global fluctuations in the density of states of the SYK model. The connected contributions to the moments are much larger than the standard RMT correlations. We provide a diagrammatic description of the leading behavior of these connected moments in terms of 1PI cactus graphs, and derive a vector model of the couplings which reproduces these results. We generalize these results to the first subleading corrections, and to fluctuations of correlation functions. In either case, the new set of correlations are not associated with (and are much larger than) the ones given by topological wormholes. The connected contributions that we discuss are the beginning of an infinite series of terms, associated with more and more information about the ensemble of couplings, which hints towards the dual of a single realization. In particular, we suggest that incorporating them in the gravity description requires the introduction of new, lighter and lighter, fields in the bulk with fluctuating boundary couplings.

We analyse the connections between the Wheeler DeWitt approach for two dimensional quantum gravity and holography, focusing mainly in the case of Liouville theory coupled to c = 1 matter. Our motivation is to understand whether some form of averaging is essential for the boundary theory, if we wish to describe the bulk quantum gravity path integral of this two dimensional example. The analysis hence, is in a spirit similar to the recent studies of Jackiw-Teitelboim (JT)-gravity. Macroscopic loop operators define the asymptotic region on which the holographic boundary dual could be expected to reside. Matrix quantum mechanics and the associated double scaled fermionic field theory, are providing the complete dynamics of such two-dimensional universes with c=1 matter, including the effects of topology change.  On the other hand, if we try to associate a Hilbert space to a single boundary dual living on the loop, it cannot contain all the information present in the non-perturbative bulk quantum gravity path integral and MQM.

For a QFT with U(1) global symmetry, a resolution of the reduced 

density matrix via the U(1) subregion-charge defined on the entangled 

region is allowed. This indicates the existence of a refinement of the 

usual entanglement entropy, which is the so-called "Symmetry-resolved 

entanglement entropy(SREE)". In this talk, I will discuss the 

symmetry-resolved entanglement in the context of AdS3/CFT2. I will 

start from a toy holographic model: Three-dimensional U(1) 

Chern-Simons Einstein gravity. The calculations of the SREE rely on 

the CFT charged moments. I will show that the holographic dual of the 

CFT charged moments can be simpily realized by inserting a U(1) Wilson 

line inside the bulk, with its holonomy being identified with the 

monodromy generated by the boundary vertex operators. The resulting 

U(1) SREE exhibits a universal equipartition behavior of the 

entanglement. I will also discuss our recent progress on the two 

disjoint intervals case and the generalization of SREE in higher spin 

symmetry case, i.e W3 CFT and holographic higher spin-3 gravity.

Abstract:

I present recent work of our group on realizing computational complexity in conformal field theories in view of relating it holographically to complexity proposals in AdS gravity. Gates and cost functions in the CFT are introduced and used for a complexity definition based on geometric actions on Virasoro and Kac-Moody orbits. We discuss a relation to the Euler-Arnold approach in Hamiltonian dynamics. In a complementary project, we developed a new method for evaluating modular flows for 1+1-dimensional chiral fermions, working directly from the resolvent in complex analysis. Both projects provide new ingredients for exploring the connection between spacetime and entanglement.



Talk based on 2004.03619 and 2008.07532

Abstract: 

Recent work on quantum gravity has revealed deep connections with subjects like

quantum information, statistical physics and quantum chaos. In particular, low-energy effective

field theories that include gravity turn out to have more access to high-energy degrees of freedom

than their non-gravitational Wilsonian counterparts. While precise microscopic high-energy information

is inaccessible, certain statistical high-energy information does manifest itself in an interesting way at low

energies. I will describe some recent work trying to make this connection more precise, and explain how

it connects to issues like wormholes and averaging over theories.

In gauge/gravity duality, the information regarding the gravitational geometry (e.g., black hole and smooth exterior geometry) has to be encoded in gauge theory. Clearly, the color degrees of freedom (matrix degrees of freedom) should play the key role, because the duality can hold even when the gauge theory side is a matrix model. In this talk, I will suggest a simple way of encoding the geometry to matrices, along the line of Witten's work on the effective action of D-branes and strings, and the Matrix Theory conjecture by Banks, Fischler, Shenker and Susskind. Roughly speaking, eigenvalues of matrices can be identified with the location of the D-brane probe or extended objects such as black hole. 



Actually there is a famous argument against such simple interpretation advocated by Polchinski in 1998. His argument used generic properties of large-N gauge theory to show that the ground-state wave function delocalizes at large N, leading to a conflict with the locality in the bulk geometry. We show that this argument is not correct: the ground-state wave function does not delocalize, and there is no conflict with the locality of the bulk geometry. In order to understand how the old argument fails, recently-discovered connection between color confinement and Bose-Einstein condensation is useful. This confinement-BEC connection has a striking consequence: in the SU(N) gauge theory, there is a partially-deconfined phase in which an SU(M)-subgroup is deconfined. Partial deconfinement, combined with the "eigenvalue = location" picture, provides us with a natural scenario to realize the idea in BFSS Matrix Theory conjecture --- extended objects, such as black hole, are realized as bound states of D-branes and strings, that look like non-commutative blocks in big matrices --- in the Maldacena-type gauge/gravity duality. In the large-N limit, various many-body states can be realized by considering block-diagonal matrix configurations, similarly to the BFSS proposal. Therefore, the large-N limit of gauge theory can be interpreted as the second quantization of the gravity side. 



If time permits, we will discuss how we might be able to check this proposal quantitatively, via classical or quantum simulations.