Overview
This workshop aims to bring together experts on holography, quantum chaos, and black hole physics to report on new developments, reflect on the state of the field, have fruitful discussions about open problems, and foster collaboration. There will be about 4 talks per day to leave plenty of time for discussions in a friendly atmosphere with a small group of people.
Dates: 3-5 July 2023
Location: Wadham College, University of Oxford
Organizers: Mark Mezei ( mezei [at] maths.ox.co.uk ) and Felix Haehl ( f.m.haehl [at] soton.ac.uk )
Schedule
Speakers and talks
Title: On the discrete spacetime of the quantum disk
Abstract: The idea of spacetime discreteness in the UV has been fraught with issues due to its strong effects in the IR. Nevertheless, recent work on the double scaled SYK model (DSSYK) demonstrates that smooth spacetime can emerge from a discrete lattice-like structure. Similar lattice-like spacetimes have been studied by mathematicians and are known as quantum spacetimes due to their non-commutating coordinates variables. I will review how to define such a quantum spacetime, focusing on the quantum hyperbolic disk, and analyze the physics of matter living on this non-commutative spacetime.
Abstract: The idea of spacetime discreteness in the UV has been fraught with issues due to its strong effects in the IR. Nevertheless, recent work on the double scaled SYK model (DSSYK) demonstrates that smooth spacetime can emerge from a discrete lattice-like structure. Similar lattice-like spacetimes have been studied by mathematicians and are known as quantum spacetimes due to their non-commutating coordinates variables. I will review how to define such a quantum spacetime, focusing on the quantum hyperbolic disk, and analyze the physics of matter living on this non-commutative spacetime.
Title: Quantum chaos in two-dimensional gravity
Abstract: Spectra and wave functions of quantum chaotic systems show universal correlations which have been described in terms of a multitude of concepts, including random matrix theory, diagrammatic perturbation theory, or quantum field theory. While most of these were developed in fields such as condensed matter or many body physics, more recent work aims to extend the concept of quantum chaotic universality to gravity. These ideas assume their most concrete form in the construction of a two-dimensional holographic correspondence, and the observation of chaotic correlations in a gravitational path integral. In this talk, we will review these developments and reason that the completion of the holographic principle to one capturing the full chaotic structure of the bulk spectrum requires the extension of the semiclassical gravitational path integral by topological string theory. We will show that the string theory in question contains the Efetov nonlinear sigma model as an ergodic limit, which demonstrates presence of universal spectral correlations in the bulk micro state spectrum.
Abstract: Spectra and wave functions of quantum chaotic systems show universal correlations which have been described in terms of a multitude of concepts, including random matrix theory, diagrammatic perturbation theory, or quantum field theory. While most of these were developed in fields such as condensed matter or many body physics, more recent work aims to extend the concept of quantum chaotic universality to gravity. These ideas assume their most concrete form in the construction of a two-dimensional holographic correspondence, and the observation of chaotic correlations in a gravitational path integral. In this talk, we will review these developments and reason that the completion of the holographic principle to one capturing the full chaotic structure of the bulk spectrum requires the extension of the semiclassical gravitational path integral by topological string theory. We will show that the string theory in question contains the Efetov nonlinear sigma model as an ergodic limit, which demonstrates presence of universal spectral correlations in the bulk micro state spectrum.
Title: Fermionic Matrix Quantum Mechanics
Abstract: We discuss matrix models built entirely out of fermionic degrees of freedom at both vanishing and finite temperature. We consider real time features and properties of the thermal partition function. The ‘t Hooft limit, among others, is also considered.
Abstract: We discuss matrix models built entirely out of fermionic degrees of freedom at both vanishing and finite temperature. We consider real time features and properties of the thermal partition function. The ‘t Hooft limit, among others, is also considered.
Title: EFT thinking applied to 2d gravity and chaos
Abstract: Many effective field theorists hope that gravity is the symmetry broken phase of some yet-undiscovered theory with some yet-undiscovered symmetry, with the goldstone mode of this broken symmetry being the graviton. We do not make any progress on this difficult problem. However, we study something conceptually related in the context of Euclidean JT gravity. More precisely, we have come to appreciate that the Euclidean JT path integral is perturbatively equivalent to a matrix integral, and the path integral with fixed boundary conditions is equivalent to Wilson-loop type observables in the matrix model. I will review this equivalence and explain how it can be understood as the symmetry broken phase of a class of matrix models with a global symmetry, and where the symmetry preserving phase has no gravity interpretation. The result of this is that the chaotic dynamics of random matrix theory can be thought of as arising from the goldstones modes of the symmetry broken phase.
Abstract: Many effective field theorists hope that gravity is the symmetry broken phase of some yet-undiscovered theory with some yet-undiscovered symmetry, with the goldstone mode of this broken symmetry being the graviton. We do not make any progress on this difficult problem. However, we study something conceptually related in the context of Euclidean JT gravity. More precisely, we have come to appreciate that the Euclidean JT path integral is perturbatively equivalent to a matrix integral, and the path integral with fixed boundary conditions is equivalent to Wilson-loop type observables in the matrix model. I will review this equivalence and explain how it can be understood as the symmetry broken phase of a class of matrix models with a global symmetry, and where the symmetry preserving phase has no gravity interpretation. The result of this is that the chaotic dynamics of random matrix theory can be thought of as arising from the goldstones modes of the symmetry broken phase.
Title: Approximate CFTs and Random Tensor Models
Title: The Page curve from the entanglement membrane
Abstract: We study entanglement dynamics in toy models of black hole information built out of chaotic many-body quantum systems, by utilising a coarse-grained description of entanglement dynamics in such systems known as the `entanglement membrane'. We show that in these models the Page curve associated to the entropy of Hawking radiation arises from a transition in the entanglement membrane around the Page time, in an analogous manner to the change in quantum extremal surfaces that leads to the Page curve in semi-classical gravity. We also use the entanglement membrane prescription to study the Hayden-Preskill protocol, and demonstrate how information initially encoded in the black hole is rapidly transferred to the radiation around the Page time. Our results relate recent developments in black hole information to generic features of entanglement dynamics in chaotic many-body quantum systems.
Abstract: We study entanglement dynamics in toy models of black hole information built out of chaotic many-body quantum systems, by utilising a coarse-grained description of entanglement dynamics in such systems known as the `entanglement membrane'. We show that in these models the Page curve associated to the entropy of Hawking radiation arises from a transition in the entanglement membrane around the Page time, in an analogous manner to the change in quantum extremal surfaces that leads to the Page curve in semi-classical gravity. We also use the entanglement membrane prescription to study the Hayden-Preskill protocol, and demonstrate how information initially encoded in the black hole is rapidly transferred to the radiation around the Page time. Our results relate recent developments in black hole information to generic features of entanglement dynamics in chaotic many-body quantum systems.
Title: Keeping matter in the loop in 3d quantum gravity
Abstract:
Abstract:
Title: Wheeler-DeWitt states of black hole and cosmological interiors
Abstract: In AdS/CFT, the renormalization group flow of coupling constants is described by the radial evolution of bulk fields, using the bulk equations of motion. Horizons in the bulk correspond to the far IR of the renormalisation group, but the bulk evolution does not stop there. The bulk fields continue to evolve in the “interior” beyond the horizon, with the evolution now unfolding in time rather than space. In the interior the same bulk equations of motion now define a Wheeler-DeWitt wave function rather than a boundary partition function. I will explain how Hamilton-Jacobi theory gives a unified description of the exterior partition function of coupling constants and the interior wave function. Once this picture is established in AdS/CFT, I will describe how it can be applied also in de Sitter spacetimes. There, the same equations defining Wheeler-DeWitt states near future infinity are shown to define quantum mechanical partition functions in the static patch.
Abstract: In AdS/CFT, the renormalization group flow of coupling constants is described by the radial evolution of bulk fields, using the bulk equations of motion. Horizons in the bulk correspond to the far IR of the renormalisation group, but the bulk evolution does not stop there. The bulk fields continue to evolve in the “interior” beyond the horizon, with the evolution now unfolding in time rather than space. In the interior the same bulk equations of motion now define a Wheeler-DeWitt wave function rather than a boundary partition function. I will explain how Hamilton-Jacobi theory gives a unified description of the exterior partition function of coupling constants and the interior wave function. Once this picture is established in AdS/CFT, I will describe how it can be applied also in de Sitter spacetimes. There, the same equations defining Wheeler-DeWitt states near future infinity are shown to define quantum mechanical partition functions in the static patch.
Title: Non-perturbative de Sitter JT gravity
Abstract: The goal of this talk is to present the solution to the de Sitter version of JT gravity. Upon careful treatment of its measure, the amplitudes of this model are a particular analytic continuation of those of its Euclidean AdS version. In particular, the effective string coupling g of the model is pure imaginary so that the effective number of degrees of freedom ~1/g^2 is large and negative.
Abstract: The goal of this talk is to present the solution to the de Sitter version of JT gravity. Upon careful treatment of its measure, the amplitudes of this model are a particular analytic continuation of those of its Euclidean AdS version. In particular, the effective string coupling g of the model is pure imaginary so that the effective number of degrees of freedom ~1/g^2 is large and negative.
Title: Quantum Bounds and the Fluctuation Dissipation Theorema
Abstract: The quantum fluctuation-dissipation theorem (the KMS conditions) acts as a mechanism for bounding the time scales of correlation functions. By rewriting the OTOC in a replicated space, I will show that the quantum bound to chaos is a direct consequence of the KMS condition, applied to a particular pair of two-time correlation-response functions. This will allow me to derive bounds on "generalized Lyapunov exponents," a measure of the multifractality of the underlying chaotic dynamics. Encouraged by these results, I will describe how quantum fluctuation-dissipation relations can act as a blurring of the time dependence of correlations. Finally, I will discuss our attempts to understand the Planckian bound from two-point correlation functions. Based on: SP Foini Kurchan https://arxiv.org/abs/2204.11679 and SP Kurchan https://arxiv.org/abs/2212.10123
Abstract: The quantum fluctuation-dissipation theorem (the KMS conditions) acts as a mechanism for bounding the time scales of correlation functions. By rewriting the OTOC in a replicated space, I will show that the quantum bound to chaos is a direct consequence of the KMS condition, applied to a particular pair of two-time correlation-response functions. This will allow me to derive bounds on "generalized Lyapunov exponents," a measure of the multifractality of the underlying chaotic dynamics. Encouraged by these results, I will describe how quantum fluctuation-dissipation relations can act as a blurring of the time dependence of correlations. Finally, I will discuss our attempts to understand the Planckian bound from two-point correlation functions. Based on: SP Foini Kurchan https://arxiv.org/abs/2204.11679 and SP Kurchan https://arxiv.org/abs/2212.10123
Title: Creases, corners and caustics: non-smooth structures on black hole horizons
Abstract: The event horizon of a dynamical black hole is generically a non-smooth hypersurface. I shall describe the types of non-smooth structure that can arise on a horizon that is smooth at late time. This includes creases, corners and caustic points. I shall discuss ``perestroikas'' of these structures, in which they undergo a qualitative change at an instant of time. A crease perestroika gives an exact local description of the event horizon near the ``instant of merger'' of a generic black hole merger. Other crease perestroikas describe horizon nucleation or collapse of a hole in a toroidal horizon. I shall discuss the possibility that creases contribute to black hole entropy, and the implications of non-smoothness for higher derivative terms in black hole entropy. This talk is based on joint work with Maxime Gadioux.
Abstract: The event horizon of a dynamical black hole is generically a non-smooth hypersurface. I shall describe the types of non-smooth structure that can arise on a horizon that is smooth at late time. This includes creases, corners and caustic points. I shall discuss ``perestroikas'' of these structures, in which they undergo a qualitative change at an instant of time. A crease perestroika gives an exact local description of the event horizon near the ``instant of merger'' of a generic black hole merger. Other crease perestroikas describe horizon nucleation or collapse of a hole in a toroidal horizon. I shall discuss the possibility that creases contribute to black hole entropy, and the implications of non-smoothness for higher derivative terms in black hole entropy. This talk is based on joint work with Maxime Gadioux.
Title: AdS/CFT as the “harmonic oscillator” of holography
Abstract: (Almost) all known examples of non-AdS holography can be mapped back to AdS/CFT via non-trivial analytic continuation of parameters and variables. This includes the duality involving non-conformal branes, non-relativistic holography, Rindler fluid holography and holography for cosmology. I will summarize these results and then add another entry to this list: flat space holography from AdS/CFT.
Abstract: (Almost) all known examples of non-AdS holography can be mapped back to AdS/CFT via non-trivial analytic continuation of parameters and variables. This includes the duality involving non-conformal branes, non-relativistic holography, Rindler fluid holography and holography for cosmology. I will summarize these results and then add another entry to this list: flat space holography from AdS/CFT.
Title: Firewalls from wormholes
Abstract: Spacetime wormholes can lead to surprises in black hole physics. We show that a very old black hole can tunnel to a white hole/firewall by emitting a large baby universe. We study the process for a perturbed thermofield double black hole in Jackiw-Teitelboim (JT) gravity, using the lowest order (genus one) spacetime wormhole that corresponds to single baby-universe emission. The probability for tunneling to a white hole is proportional to t2e−2S where t is the age of the black hole and S is the entropy of one black hole.
Abstract: Spacetime wormholes can lead to surprises in black hole physics. We show that a very old black hole can tunnel to a white hole/firewall by emitting a large baby universe. We study the process for a perturbed thermofield double black hole in Jackiw-Teitelboim (JT) gravity, using the lowest order (genus one) spacetime wormhole that corresponds to single baby-universe emission. The probability for tunneling to a white hole is proportional to t2e−2S where t is the age of the black hole and S is the entropy of one black hole.
Participants
A list of participants can be found HERE.
Location and Travel
This workshop will be hosted by Wadham College in Oxford (Parks Rd, Oxford OX1 3PN), in the "Okinaga Room". The entrance to the Okinaga room is marked with A on THIS map.
Accommodation with breakfast will also be provided in Wadham College.
You can walk to Wadham College from the train and bus stations. You can enter the college through the wooden gate that you can see HERE. Once you enter, on your right you will find the reception (Lodge), who will assist you.
The official University of Oxford travel guide can be found HERE.
Heathrow is the most convenient airport to use. The Airline Coach service is very convenient from Heathrow.
The other airports are harder to reach: the Airline Coach services Gatwick as well, but the ride may take very long due to traffic. The bus and train services from Luton also take a long time, but you can get to Oxford with taxi fairly quickly from Luton (but it's expensive). Stansted is the farthest airport from Oxford, but can be reached with train or bus.
Registration
Official registration is now closed. The sign-up sheet can still be found HERE, but it's unlikely that any new applications can be accepted.
We will provide most meals (including a conference dinner) for accepted participants on the days of the workshop. Other expenses have to be covered by participants.
There is a registration fee of GBP 30 that should be paid HERE.
