Online Workshop on Quantum Gravity, Holography and Quantum Information

Contribution List

25. Opening address

Dieter Lüst

17/03/2021, 10:20

1. Towards a Swampland Global Symmetry Conjecture

Arthur Hebecker

17/03/2021, 10:30

Given that exact global symmetries are forbidden by quantum gravity, it is natural to expect that bounds on the quality of approximate global symmetries exist. So far, holographic arguments have only been provided for the former claim. I will discuss a classification of approximate global symmetries and describe a simple argument, based the Weak Gravity Conjecture, for a quantitative bound on...

2. Simple Euclidean wormholes might not contribute in the path integral

Thomas Van Riet

17/03/2021, 11:30

I present evidence, both from a GR and a holographic viewpoint, that Coleman's Euclidean axion wormholes do not contribute to the path integral.

45' talk + 15' discussion

3. The OPE Randomness Hypothesis and Euclidean Wormholes

Alex Belin

17/03/2021, 13:30

Recent developments in holography indicate that the semi-classical Euclidean path-integral of Einstein gravity is much more powerful than previously anticipated. It is capable of reproducing a unitary Page curve for black hole evaporation, and can even capture some features of the discrete nature of black hole microstates. Wormhole geometries play a key role in this context. I will propose a...

4. Quantum Complexity, Integrability, and Chaos

Vijay Balasubramanian

17/03/2021, 14:30

The states of quantum systems grow in complexity over time as entanglement spreads between degrees of freedom. Following ideas in computer science, we formulate the complexity of evolution as the length of the shortest geodesic on the unitary group manifold between the identity and the time evolution operator, and use the SYK family of models with N fermions to study this quantity in free,...

5. Discussion session

Elias Kiritsis

17/03/2021, 15:30

6. Islands and Hawking radiation correlations of evaporating black holes

Prem Kumar

17/03/2021, 16:30

We consider the effect of shockwaves on the entanglement structure of black holes. We examine the correlations in generic subsets of the Hawking radiation emitted by evaporating black holes following the shockwave insertion and find a zoo of competing island saddle points for the associated entanglement entropies. By computing the mutual information between early and late modes we establish...

7. Comments on Euclidean wormholes and holography

Panos Betzios

17/03/2021, 17:30

Euclidean wormholes comprise exotic types of gravitational solutions, that still challenge our physical intuition and understanding. In the first part of the talk, I will analyse asymptotically AdS wormhole solutions in the context of holography. From a bottom up perspective a study of correlation functions of local and non-local operators indicates the universal properties that any putative...

8. Free discussion

17/03/2021, 18:30

9. Phases of Holographic Interfaces

Costas Bachas

18/03/2021, 10:30

Domain walls between Anti-de Sitter vacua are important for the study of the string-theory landscape, and enter in recent toy models of black hole evaporation. In this talk I will describe the phase diagram of a simple 2+1 dimensional model of thin domain walls anchored at the AdS boundary, and I will comment on its dual holographic interpretation.

45' talk + 15' discussion

10. Towards a microscopic model of AdS fragmentation

Tarek Anous

18/03/2021, 11:30

A salient feature of black holes near extremality is the appearance of an AdS$_2$ throat in their near-horizon geometry. Depending on the underlying theory, these AdS$_2$ throats may be unstable to fragmentation, wherein a single throat is instead replaced by a tree-like structure of branched AdS$_2$ throats. For Einstein-Maxwell theory, the underlying reason behind this instability is the...

11. Pole skipping away from maximal chaos

Gábor Sárosi

18/03/2021, 13:30

The pole skipping phenomenon is a subtle effect in the thermal energy density retarded two point function at a special point in the complex frequency and momentum planes. For maximally chaotic theories, this special point is related to data characterising the butterfly effect, and is explained by a common dynamical origin of energy transport and scrambling. I will argue that pole skipping also...

12. A Wheeler DeWitt approach for Liouville quantum gravity

Olga Papdoulaki

18/03/2021, 14:30

I will present the connection between the Wheeler-DeWitt approach for two-dimensional quantum gravity and holography, focusing in the case of Liouville theory coupled to c = 1 matter. The analysis is in a spirit similar to the recent studies of Jackiw-Teitelboim gravity. Matrix quantum mechanics and the associated double scaled fermionic field theory, are providing the complete dynamics of...

13. Discussion session

Jan de Boer

18/03/2021, 15:30

15. On the geometry of quantum complexity

Roberto Auzzi

18/03/2021, 16:30

Computational complexity is a quantum information concept that recently has found applications in holography. I will consider quantum computational complexity for n qubits using Nielsen's geometrical approach. In the definition of complexity there is a big amount of arbitrariness due to the choice of the penalty factors, which parameterize the cost of the elementary computational gates. In...

16. Complexity for CFTs in General Dimensions

Shira Chapman

18/03/2021, 17:30

In this talk I will discuss circuit complexity in the setting of higher dimensional conformal field theories. I will consider unitary gates built from a representation of the conformal group, two different circuit cost functions defined using either the Fubini-Study metric or the one-norm, and paths that start from an initial spinless primary state. We will see that the resulting Fubini-Study...

17. Free discussion

18/03/2021, 18:30

18. Page Curve from Holographic Moving Mirror and End of the World brane

Tadashi Takayanagi

19/03/2021, 10:30

In this talk we calculate the entanglement entropy in the presence of a moving mirror in a CFT. We employ the AdS/BCFT construction to describe a gravity dual of moving mirrors. We will show that the time evolution of entanglement entropy for a class of moving mirror, which models an evaporating black hole, follows an ideal page curve. In this gravity dual of this model and also in earlier...

19. The principle of holography of information and its low-energy tests

Suvrat Raju

19/03/2021, 11:30

The principle of holography of information states that, in any theory of quantum gravity, a copy of all the information available on a Cauchy slice is also available near the boundary of the slice. This principle can be made precise and proved, under weak assumptions, for theories of gravity in AdS and in flat space and it has interesting implications for black holes. In this talk, we will...

21. Discussion session: Holographic Complexity

Johanna Erdmenger

19/03/2021, 13:30

Computational complexity is a notion from information theory, initially defined for finite-dimensional systems, measuring the number of gates that have to be applied to a given reference state to reach a target state. Susskind’s proposals for defining computational complexity also for characterising quantum properties black holes have triggered significant interest in defining computational...

20. The Unreasonable Effectiveness of Higher-Derivative Supergravity in AdS_4 Holography

Nikolay Bobev

19/03/2021, 14:30

I will describe the four-derivative corrections to four-dimensional N=2 minimal gauged supergravity and show that they are controlled by two constants. Interestingly, the solutions of the equations of motion in the two-derivative theory are not modified by the higher-derivative corrections. I will use this to arrive at a general formula for the regularized on-shell action for any...

22. Saturons

Gia Dvali

19/03/2021, 16:00

We introduce the concept of saturons, systems that saturate a certain bound on entropy, which is imposed
by S-matrix and unitarity. Such objects share certain niversal properties (e.g., the area-law of entropy, near-thermal emission, inner entanglement, ...) that goes well beyond gravity. We give an example from QCD. We show that black holes and de Sitter are saturons and this determines...

23. Quantum BTZ black hole

Roberto Emparan

19/03/2021, 17:00

The study of quantum effects on black holes including their gravitational backreaction is an important but notoriously hard problem. I will begin by reviewing how the framework of braneworld holography allows to solve it for strongly-coupled quantum conformal fields. Then I will describe a holographic construction of quantum rotating BTZ black holes (quBTZ) using an exact dual four-dimensional...

24. Outlook and discussion

Roberto Emparan

19/03/2021, 18:00

14. Mini-break