- Damian Galante (King's College London)
- "RG Flows of SYK, holography & cosmology"
[Abstract] [pdf]
Abstract
I will present new solvable relevant deformations of the SYK model. Remarkably, these models are computationally tractable in the strongly coupled regime, both numerically and analytically, and, at large N, they exhibit novel infrared behaviour. They can also be holographically mapped to dilaton-gravity theories in 2d. In this talk, I will present some of the salient features of these models and discuss possible applications to holography in de Sitter space.
- Dongsheng Ge (Osaka university)
- "Boundary induced dynamical phase transition via inhomogeous quenches "
[Abstract] [pdf]
Abstract
Boundary effects play an interesting role in the finite-size physical systems.
Those are reminiscent of the choices of the boundary conditions. In this work, we study
the boundary induced dynamical properties in the “1+1”-dimensional critical systems,
driven by the inhomogeneous quenches of SSD and Möbius types. We find that different boundary
conditions measured by the boundary entropy lead to different scenarios of phase transitions.
We give a holographic interpretation in terms of intersecting branes in AdS3.
- Felix Haehl (University of Southampton)
- "Discovering Euclidean wormholes in 2d CFTs from quantum chaos and number theory" [pdf]
- Jonathan Harper (Yukawa Institute for Theoretical Physics, Kyoto University)
- "Timelike entanglement entropy"
[Abstract]
Abstract
We define a new complex-valued measure of information called the timelike entanglement entropy (EE) which in the boundary theory can be viewed as a Wick rotation that changes a spacelike boundary subregion to a timelike one. We argue that timelike EE should be correctly interpreted as another measure previously considered, the pseudo entropy, which is the von Neumann entropy of a reduced transition matrix. Our results strongly imply that the imaginary part of the pseudo entropy describes an emergent time which generalizes the notion of an emergent space from quantum entanglement. For holographic systems we define the timelike EE as the total complex valued area of a particular stationary combination of both space and timelike extremal surfaces which are homologous to the boundary region. For the examples considered we find explicit matching of our optimization procedure and the careful implementation of the Wick rotation in the boundary CFT.
- Song He (Jilin University)
- "Holographic torus correlators of stress tensor in AdS3/CFT2"
[Abstract] [pdf]
Abstract
In the context of AdS3/CFT2AdS3/CFT2, we investigate holographic correlators of the stress tensor of a conformal field theory (CFT) on a torus in this work. To calculate the correlators of the stress tensor, we employ the Einstein-Hilbert theory of gravity and perturbatively solve Einstein's equation in the bulk. We offer an explicit prescription to develop a recurrence relation that makes it simple to compute higher point correlators. The correlators and the recurrence relation are found to be consistent with what is known in CFTs. Following the spirit of the proposed cutoff AdSAdS/TTˉTTˉ CFT holography, we then expand our computation program to investigate holographic torus correlators at a finite cutoff in the AdS3AdS3. A parallel recurrence relation associated with higher point correlators can be obtained.
- Masazumi Honda (Yukawa Institute for Theoretical Physics, Kyoto University)
- "Quantum error correction and Gauge theory"
- Keisuke Izumi (Kobayashi Maskawa Institute, Department of Mathematics, Nagoya University)
- "Area bound in weak gravity region"
[Abstract]
Abstract
Riemannian Penrose inequality gives the upper bound of the area of the
outermost minimal surface in an asymptotically flat spatial surface with
nonnegative curvature. The inequality shows, roughly speaking, the
upper-bound area of black hole horizon, that is, it can be applied in a
region with strong gravitational field.
We deform this inequality so that it can be applied in weak gravitational
field. Hence, we show a generalized area inequality.
- Shunichiro Kinoshita (Nihon University)
- "Stark effect and dissociation of mesons in holographic conductor"
[Abstract] [pdf]
Abstract
We study the meson spectrum of the N = 4 supersymmetric Yang-Mills theory with N = 2 fundamental hypermultiplets for finite electric field by using the D3/D7 model. The spectrum for scalar and vector mesons is computed by analyzing the (quasi-)normal modes for the fluctuations of the D7-brane embedding and gauge fields. In the presence of an electric field, two different phases in the background are realized: stable meson phase and dissociation phase. In this presentation, we show the meson spectrum of scalar and vector mesons for all range of the electric field.
- Johannes Knaute (Racah Institute of Physics, Hebrew University of Jerusalem)
- "Entanglement and confinement in quantum field and lattice gauge theories"
[Abstract] [pdf]
Abstract
Quantum information concepts can provide new insights for the understanding of emergent phenomena of fundamental systems in high-energy and gravitational physics. In this talk I present an overview of recent work on the interplay of entanglement and confinement properties in quantum field and lattice gauge theories.
In the first part I propose to use quantum information notions to characterize thermally induced melting of nonperturbative meson bound states at high temperatures. I apply tensor network simulations to investigate this idea in static and dynamical settings within the (1+1)-dimensional Ising quantum field theory. I then discuss the impact of meson confinement on the dynamics of entanglement spectra after quantum quenches and discuss the results in the context of dynamical quantum phase transitions.
In the second part I explore the use of lattice gauge theory tensor networks based on two-dimensional projected entangled pair states for the calculation of entanglement measures. In particular, I present results for the long-range behavior of the Renyi entropy (for arbitrary gauge groups in the thermodynamic limit) and relate its behavior to (de)confinement properties.
Based on arXiv:2206.10528, 2210.15682 and upcoming work.
- Yuya Kusuki (California Institute of Technology)
- "AdS/BCFT from Conformal Bootstrap"
[Abstract] [pdf]
Abstract
We consider gravity with branes and massive particles, which has many unclear aspects. For example, we do not know how to understand some problematic configurations, like brane self-intersections, negative tension branes, and spinning particles interacting with branes. We address these issues through AdS/BCFT. We solve a related conformal bootstrap and show that the self-intersection can be avoided by the black hole formation. We also reveal how to resolve the other problems in AdS/BCFT using the bootstrap.
In the later part, we give the resolution of the same problems from the gravity side. For this purpose, we develop a simple way to construct gravity with branes and particles by cutting and pasting. The solution from this construction tells us how to resolve the issues from the gravity side, which is completely consistent with the CFT result.
As a bonus, we find a refined formula for the holographic Rényi entropy, which appears to be crucial to correctly reproduce the boundary entropy term.
- Kengo Maeda (Shibaura Institute Of Technology)
- "Semiclassical Einstein equations from holography and boundary dynamics"
[Abstract]
Abstract
We derive the semiclassical Einstein equations sourced with boundary CFT stress-energy tensor. Analyzing perturbations of the holographic semiclassical Einstein equations, we find a universal parameter γd which controls the contribution from boundary CFTs and specifies dynamics on the AdS boundary. As a simple example, we examine the semiclassical Einstein equations in 3-dimensions with 4-dimensional AdS gravity dual, and show that the boundary BTZ black hole with vanishing expectation value of the stress-energy tensor exhibits instability due to the backreaction from quantum stress-energy tensor when the parameter γd exceeds a certain critical value.
- Rene Meyer (Institute for Theoretical Physics and Astrophysics, Julius-Maximilians-University Wuerzburg)
- "Symmetry-Resolved Entanglement in AdS and in CFT"
[Abstract] [pdf]
Abstract
I will discuss recent new examples of quantum information measures providing new links between quantum information, holography and quantum gravity: I will first introduce a refinement of the usual entanglement entropy for theories with global conserved charges, the so-called symmetry resolved entanglement entropy, and discuss its implementation in AdS3/CFT2 (2012.11274, 2108.09210). I will in particular discuss the structure of entanglement in different charge sectors, which turns out trivial in theories with U(1) Kac-Moody symmetry (so-called equipartition of entanglement), and non-trivial in W3 symmetric CFTs (2202.11111). Finally, I will present recent work (2212.09767) which employs boundary conformal field theory techniques to obtain exact results for the symmetry-resolved entanglement and in particular for the equipartition property in U(1) Kac-Moody symmetric CFTs. I will end with an outlook on future applications of the idea of symmetry resolution in AdS/CFT, string theory, and quantum gravity in general.
- Pratik Nandy (Yukawa Institute for Theoretical Physics, Kyoto University)
- "Operator growth and quantum chaos: lessons from SYK"
[Abstract] [pdf]
Abstract
We initialize the understanding of scrambling phenomena in inhomogeneous conformal field theories (CFTs), by studying the operator growth from the perspective of Krylov complexity, We consider 2d systems deformed by the Mobius and sine-squared deformation. We present some novel results obtained by such inhomogeneous evolution and discuss some interpretations both from CFT and holographic side. The work is in progress with Masahiro Nozaki (KITS/iTHEMS) and Shinsei Ryu (Princeton).
- Tokiro Numasawa (Institute for Solid State Physics, University of Tokyo)
- "On SYK traversable wormhole with imperfectly correlated disorders"
[Abstract]
Abstract
In this talk we study the phase structure of two Sachdev-Ye-Kitaev models (L-system and R-system) coupled by a simple interaction, with imperfectly correlated disorder. When the disorder of the two systems are perfectly correlated, this model is known to exhibit a phase transition at a finite temperature between the two-black hole phase at high-temperature and the traversable wormhole phase at low temperature. We find that, as the correlation of the random couplings is decreased, the critical temperature becomes lower. At the same time, the transmission between L-system and R-system in the low-temperature phase becomes more suppressed, while the chaos exponent of the whole system becomes larger. Interestingly we also observe that when the correlation is smaller than some q-dependent critical value the phase transition completely disappears in the entire parameter space. At zero temperature, the energy gap becomes larger as we decrease the correlation. We also use a generalized thermofield double state as a variational state. Interestingly, this state coincide with the ground state in the large q limit.
- Shan-Ming Ruan (Yukawa Institute for Theoretical Physics, Kyoto University)
- "A half de Sitter Holography"
[Abstract] [pdf]
Abstract
A long-standing and intriguing question is: does the holographic principle apply to cosmologies like de Sitter spacetime? In this work, we consider a half dS spacetime which is closed by a timelike boundary, as a version of de Sitter holography. By analyzing the holographic entanglement entropy in this space and comparing it with that in AdS/CFT, we argue that gravity on a half dS$_{d+1}$ is dual to a highly non-local field theory on dS$_d$. This non-locality causes a violation of subadditivity for holographic entanglement entropy. This is argued to be related to another observation that constant time slices in global de Sitter space overestimate the degrees of freedom by multiply counting the same Hilbert space.
- Gautam Satishchandran (Princeton University and Princeton Gravity Initiative)
- "Horizons are Watching You"
[Abstract] [pdf]
Abstract
We show that if a massive (or charged) body is put in a quantum superposition of
spatially separated states in the vicinity of a black hole or cosmological horizon, the mere
presence of the horizon will eventually destroy the coherence of the superposition. This
occurs because, in effect, the long-range fields sourced by the superposition register on
the horizon which forces the emission of entangling “soft gravitons/photons” through the
horizon. This enables the horizon to harvest “which path” information about the superposition. We provide estimates of the decoherence time for such quantum superpositions in the presence of a black hole and cosmological horizon. Additionally, we show that this decoherence is distinct from—and larger than—the decoherence resulting from the presence of thermal radiation from the horizon. Finally, we further sharpen and generalize this mechanism by recasting the gedankenexperiment in the language of (approximate) quantum error correction. This yields a complementary picture where the decoherence is due to an “eavesdropper” (Eve) inside the black hole attempting to obtain “which path” information by measuring the long-range fields of the superposed body. We compute the quantum fidelity to determine the amount of information such an interior observer can obtain, and use the information-disturbance tradeoff to give a direct relationship between the Eve’s information and the decoherence of the superposition in the exterior. In particular, we show that the decoherence of the superposition corresponds to the “optimal” measurement performable in the black hole interior. We comment on how this phenomenon can be interpreted as a low-energy probe of the so-called central dogmas of black hole and cosmological horizons.
- Jonathan Sorce (Center for Theoretical Physics, Massachusetts Institute of Technology)
- "On the unreasonable effectiveness of modular flow"
[Abstract] [pdf]
Abstract
Modular flow has proved to be an extremely useful tool for understanding entropy in quantum field theory and quantum gravity. This talk addresses the question, "Why should we expect modular flow to be so effective?" I will present a uniqueness theorem known to mathematicians, but underappreciated by physicists: that if an out-of-equilibrium state is to appear thermal with respect to some nonstandard arrow of time, then the modular flow is the only arrow of time that could possibly have this property. I will argue that this observation should be treated as the fundamental link between modular flow and physics, and discuss connections to recent results.
- Kenta Suzuki (Rikkyo University)
- "Dimensional Reduction of the S^3/WZW Duality" [pdf]
- Kotaro Tamaoka (Nihon University)
- "Linearity of mixed state measures and entanglement wedge cross section"
[Abstract]
Abstract
The holographic entanglement entropy formula suggests that the entanglement entropy for holographic states behaves like the expectation value of a linear operator, sometimes called the "area operator". In this talk, we ask similar questions about the quantum information theoretic quantities for mixed states such as entanglement of purification, reflected entropy and so forth.
- Evita M.H. Verheijden (Black Hole Initiative, Harvard University)
- "Holographic Pseudoentanglement and Cryptographic Censorship"
- Wayne Wei-en Weng (Cornell University)
- "Computable Cross Norm in Tensor Networks and Holography"
[Abstract]
Abstract
The Computable Cross Norm (CCNR) was recently discussed in arxiv:2211.11952 as a
measure of multipartite entanglement in a condensed matter context. In this short note,
we point out that it is closely related to the (2, n)-Renyi reflected entropy, which has been
studied in the context of AdS/CFT. We discuss the calculation of the CCNR in random
tensor networks as well as holographic CFTs. The holographic dual involves a backreacted
entanglement wedge cross section in a geometry sourced by Renyi-2 cosmic branes. We
perform explicit calculations for two intervals in a hyperbolic random tensor network as
well the vacuum state of a 2D holographic CFT, and analyze the occurrence of a connected-
to-disconnected phase transition. The example illustrates the validity of the proposal for
analytic continuation in holography for arbitrary values of Renyi parameter n. We comment
on a symmetry-resolved generalization of this quantity.
- Sekino Yasuhiro (Takushoku University)
- "Gauge/gravity correspondence at weak ‘t Hooft coupling and without conformal symmetry"
[Abstract] [pdf]
Abstract
We consider gauge/gravity correspondence between maximally supersymmetric Yang-Mills theories in (p+1) dimensions and superstring theories on the near-horizon limit of the Dp-brane solutions, with general p. Even though there is no conformal symmetry when p is not equal to 3, supergravity analysis suggests that at strong ‘t Hooft coupling, certain operators have power-law correlators, with powers different from the free-field values. On the other hand, it has not been understood how the free-field results can be obtained from the gravity side. In this work, we derive free-field correlators of gauge theories by considering superstrings on highly curved backgrounds. Our approach is based on the “string-bit” picture. We use the fact that the limit of weak ‘t Hooft coupling corresponds to the limit of weak string tension, in which the interaction between string bits can be ignored.
- Nicolò Zenoni (Department of Physics, Osaka University)
- "Is action complexity better for de Sitter in Jackiw-Teitelboim gravity?"
[Abstract] [pdf]
Abstract
Holographic complexity is supposed to capture the evolution of spacetime.
In (d>2)-dimensional de Sitter (dS),
due to the inflationary expansion,
both volume and action complexity diverge at a finite critical time.
Instead, in two-dimensional dS,
volume complexity is upper-bounded by an O(1) value.
In this seminar,
considering dS in Jackiw-Teitelboim gravity,
we point out that the dilaton is crucial
for complexity to behave as in higher dimensions.
In particular,
while volume complexity requires a proper
Weyl field-redefinition of the metric
to mimic the higher-dimensional result,
action complexity naturally meets this expectation.
- Masaya Amo (Yukawa Institute for Theoretical Physics, Kyoto University)
- "New Inequalities in Extended Black Hole Thermodynamics"
[Abstract]
Abstract
We conjecture new thermodynamic inequalities in stationary axisymmetric asymptotically de-Sitter spacetimes. These inequalities give us general relation between the mass, angular momentum, horizon area and the thermodynamic volume, and refine the so-called reverse isoperimetric inequality. To check the validity, we investigate these inequalities with a large number of parameter sets for a variety of spacetime solutions and find that they all satisfy our conjectures. Intriguingly, we verify that our conjectures also hold for thin black rings, which suggests that the conjectures may hold for other topologies than that with spherically topological horizon cross-section.
- Stefano Baiguera (Ben-Gurion University of the Negev)
- "The cosmological switchback effect"
[Abstract]
Abstract
The volume behind the black hole horizon was suggested as a holographic dual for the quantum computational complexity of the boundary state in AdS/CFT. This identification is strongly motivated by the switchback effect: a characteristic delay of complexity growth in reaction to an inserted perturbation, modelled as a shockwave in the bulk. Recent proposals of de Sitter (dS) holography suggest that a dual theory could be living on a stretched horizon near the cosmological horizon.
In this talk, I will show how the spacetime volume behind the cosmological horizon in Schwarzschild-dS space reacts to the insertion of shockwaves in an attempt to characterize the properties of this dual theory. I will demonstrate that a switchback effect can be observed in dS space. That is, the growth of complexity is delayed in reaction to a perturbation. This delay is longer for earlier shocks and depends on a scrambling time which is logarithmic in the strength of the shockwave and proportional to the inverse temperature of the cosmological dS horizon. This behavior is very similar to what happens for AdS black holes, albeit the geometric origin of the effect is different.
- Pablo Basteiro (Julius-Maximilians University Würzburg)
- "Quantum Complexity as Hydrodynamics"
[Abstract]
Abstract
As a new step toward defining complexity for quantum field theories, we map Nielsen operator complexity for SU(N) gates to two-dimensional hydrodynamics. We develop a tractable large N limit that leads to regular geometries on the manifold of unitaries as N is taken to infinity. To achieve this, we introduce a basis of noncommutative plane waves for the su(N) algebra and define a metric with polynomial penalty factors. Through the Euler-Arnold approach we identify incompressible inviscid hydrodynamics on the two-torus as a novel effective theory of large-qudit operator complexity. For large N, our cost function captures two essential properties of holographic complexity measures: ergodicity and conjugate points.
- Hugo A. Camargo (Gwangju Institute of Science and Technology)
- "Krylov Complexity in Free and Interacting Scalar QFTs"
[Abstract] [pdf]
Abstract
We discuss a notion of operator growth known as Krylov complexity in the context of free and interacting scalar QFTs in d-dimensions at finite temperature. We discuss its properties in the presence UV and IR cutoffs in the power spectrum and study the effects of these deformations in the context of a generalization to the universal Maldacena-Shenker-Stanford bound. We also discuss our results in the context of other approaches to probe chaos in Krylov space.
- Liangyu Chen (Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences)
- "Causal shadow and non-local modular flow"
[Abstract] [pdf]
Abstract
Causal shadows are bulk space-time regions between the entanglement wedges and the causal wedges, their existence encodes deep aspects of the entanglement wedge reconstruction in the context of subregion duality in AdS/CFT. In this paper, we study the perturbation theory of the causal shadows and their relation to the properties of the associated modular flows. We first revisit the cases of degenerate causal shadows based on known examples, and discuss the origin for their degeneracy via the local nature of the modular flow. We then focus on the perturbative case in which the CFT subregion consists of two spheres separated by a large distance L≫R1,2. The RT surfaces still agree with the causal horizons, giving a degenerate causal shadow classically. We compute the corrections to the quantum extremal surfaces (Q.E.S) from the bulk mutual information, which then give rise to a non-degenerate causal shadow at order GN. We end by discussing the causal shadow perturbation theory more generally, in particular we explore the possibility of extracting the positivity conditions characterizing perturbative causal shadows in the boundary CFTs.
- Bowen Chen (University of Warsaw)
- "Modular Parallel Transport and Modular Inclusion: A Free Fermion Study"
[Abstract]
Abstract
Modular parallel transport is a generalization of Berry phases, applied to modular (entanglement) Hamiltonians. Here we initiate the study of modular parallel transport for disjoint field theory regions. We study modular parallel transport in the kinematic space of multi-interval regions in the vacuum of 1+1-dimensional free fermion theory — one of the few theories for which modular Hamiltonians on disjoint regions are known. We compute explicitly the generators of modular parallel transport, and explain why their relatively simple form follows from a half-sided modular inclusion. We also compute explicitly the curvature two-form of modular parallel transport. We contrast all calculations with the expected behavior of modular parallel transport in holographic theories, emphasizing the role of non-local terms that couple distinct intervals.
- Charlie Cummings (University of Pennsylvania)
- "Python's Lunch of Generalized Entanglement Wedges"
[Abstract] [pdf]
Abstract
Entanglement wedge reconstruction (EWR) is a crucial component of the holographic dictionary. Given a subregion of the boundary, the EW is the bulk region that is entirely encoded in that boundary subregion. Such encoding demonstrates crucial quantum error-correcting features of the bulk/boundary dictionary. Other useful bulk regions such as the simple wedge, the causal wedge, and the python's lunch also play a crucial role in understanding the information-theoretic properties of the bulk. Recently, there has been a refinement of the usual EWR prescription: in general, one must define a "max wedge" which the relevant boundary subregion knows everything about, and a "min wedge" which the boundary subregion knows nothing about its complement, and these two wedges do not always coincide. Furthermore, Bousso and Pennington have recently generalized this max/min prescription to a bulk-bulk duality, as opposed to the usual bulk-boundary duality of AdS/CFT. In this work, we extend this bulk-bulk duality by defining the generalized causal wedge, simple wedge, and python's lunch. This is a crucial check of the consistency of their proposal, because the quantum information side is clearly defined, and must have a bulk dual if the generalized bulk-bulk duality is to hold. Furthermore, because the max/min wedges do not always coincide for bulk regions even in the classical limit (as opposed to boundary regions, where a max/min split is always a quantum effect), these generalized wedges give valuable insight into the entanglement structure of spacetime itself.
- Sayan Kumar Das (Indian Institute of Technology Kharagpur)
- "Holographic entanglement entropy for relativistic hydrodynamic flows"
[Abstract] [pdf]
Abstract
We study the behaviour of holographic entanglement entropy (HEE) in near equilibrium thermal states which are macroscopically described by conformal relativistic hydrodynamic flows dual to dynamical black brane geometries. We compute HEE for strip-shaped subsystems in boundary dimensions d=2,3,4, which provides us with general qualitative inferences on the interplay between fluid flows and entanglement dynamics. At first, we consider the zeroth order in hydrodynamic derivative expansion, holographically described by stationary boosted black branes. Working non-perturbatively in fluid velocity, we find that, as the fluid velocity approaches its relativistic upper limit, the UV regulated HEE exhibits a divergence, at arbitrary temperature. Also, the holographic mutual information between two relatively close subsystems vanishes at some critical fluid velocity and remains zero beyond it. We then compute HEE in an excited state of the fluid in the presence of a sound mode, considering first order in derivative expansion. As a simplified setup, we first work with non-dissipative dynamics in d=2, where the time evolution of HEE is studied in the presence of the sound mode and a propagating pressure pulse. In d= 4, we find that dissipative sound modes produce an additional dynamical UV divergence which is sub-leading compared to `area law divergence'. No such divergence is observed for dissipative sound mode in d=3.
- Julian De Vuyst (Okinawa Institute of Science and Technology)
- "Operational islands and black hole dissipation in JT gravity"
[Abstract]
Abstract
In this work, we revisit the problem of finding entanglement islands in 2d Jackiw-Teitelboim (JT) gravity. We implement the following adjustments to the traditional setup: (1) we do not explicitly couple to a non-gravitating system, instead we implement only pure absorption into a fiducial detector, (2) we utilise the operationally defined renormalised matter entanglement entropy, as defined by the boundary observer's wordline. We show that this leads to a unitary Page curve that we explicitly compute, with an island outside of the event horizon. Next, we extend the analysis to a charged and/or supersymmetric black hole. We find that in a certain regime the charged black hole grows first as it emits superradiation before eventually dissipating. We obtain similar results when embedding the system in a supersymmetric setting.
- Nicolas Delporte (Okinawa Institute for Science and Technology)
- "JT gravity at finite cutoff with self overlapping curves"
[Abstract]
Abstract
We will motivate the study of self-overlapping curves for 2d quantum gravity. In particular, we will explore some of their surprising geometrical and combinatorial properties and observe their relevance to the partition function of JT gravity at finite cutoff. (in collaboration with F. Ferrari and R. Pascalie)
- Merav Hadad (The Open University of Israel)
- "Correspondence between spontaneous collapse theory to black hole evaporation and"
[Abstract] [pdf]
Abstract
We consider a general correspondence between evaporating black holes and of collapsing wave functions and use this correspondence in order to explore properties of black hole evaporation. In order to do that we assume an evolution from Hartle-Hawking state to one of the superselection sectors for a specific model. The model considered is Marolf-Maxfield topological toy model for 2D gravity which gives the full spectrum of boundary theories. By equating the Marolf-Maxfield topological toy model to the Bonifacio model of spontaneous collapse theory, an equation for the evolution of a matrix element due to a generator of a parameter in MM model is obtained.
- Diksha Jain (Tata Institute of Fundamental Research, Mumbai, India)
- "S-matrix as a boundary observable"
[Abstract]
Abstract
In this talk, I will discuss our recent work on S-matrices as boundary observable and relate it to "the path integral as a function of boundary values" in flat space. In this sense, it is a boundary observable. Then I will discuss various properties of this path integral, namely, the unitarity relation, and the analytic properties etc.
- Hiroki Kanda (Yukawa Institute for Theoretical Physics, Kyoto University)
- "Brane matter and phase transitions"
- Taishi Kawamoto (Yukawa Institute for Theoretical Physics)
- "Gluing AdS/CFT"
[Abstract]
Abstract
Although AdS/CFT correspondence is one of the successful realizations of holographic principle
, the spacetimes it can tame is restricted. To gain understanding for more realistic spacetime, for example, our universe or evaporating blackhole, it is natural to generalize AdS/CFT. The primary purpose of this paper is to initiate the exploration of the concept of "holography without boundaries" through the modification of the Ad/CFT.
In concrete, we consider gluing two AdS spacetimes together along the timelike hypersurface by demanding the Israel junction condition.
From the viewpoint of the boundary field theory, the resulting bulk gravity will be dual to two TT\bar deformed field theory with induced gravity.
Moreover, we find the constraint of the boundary stress tensor and explicit configuration of the glued spacetime and its interface boundary surface in AdS3/CFT2.
- Josh Kirklin (Okinawa Institute of Science and Technology)
- "Emergent classical gauge symmetry from quantum entanglement"
[Abstract]
Abstract
We describe explicitly how entanglement between quantum mechanical subsystems can lead to emergent gauge symmetry in a classical limit. We first provide a precise characterisation of when it is consistent to treat a quantum subsystem classically in such a limit, namely: in any quantum state corresponding to a definite classical state in the classical limit, the reduced density matrix of the subsystem must be approximately proportional to a projection operator, and the projection operators for different classical subsystem states must obey an approximate mutual orthogonality condition. These are strong constraints on the entanglement structure of classical states. They generically give rise to fundamentally non-local classical degrees of freedom, which may nevertheless be accounted for using a completely local kinematical description, if one gauges this description in the right way. The mechanism we describe is very general, but for concreteness we exhibit a toy example involving three entangled spins at high angular momentum, and we also describe a significant group-theoretic generalisation of this toy example. Finally, we give evidence that this phenomenon plays a role in the emergence of bulk diffeomorphism invariance in gravity.
- Wen-Xin Lai (Yau Mathematical Sciences Center, Tsinghua University)
- "Glue-on AdS holography for TTbar-deformed CFTs"
[Abstract] [pdf]
Abstract
The $T\bar T$ (TTbar) deformation is a solvable irrelevant deformation whose properties depend on the sign of the deformation parameter $\mu$. In particular, $T\bar T$-deformed CFTs with $\mu<0$ have been proposed to be holographically dual to Einstein gravity where the metric satisfies Dirichlet boundary conditions at a finite cutoff surface. In this paper, we put forward a holographic proposal for $T\bar T$-deformed CFTs with $\mu>0$, in which case the bulk geometry is constructed by gluing a patch of AdS$_3$ to the original spacetime. As evidence, we show that the $T\bar T$ trace flow equation, the spectrum on the cylinder, and the partition function on the torus and the sphere, among other results, can all be reproduced from bulk calculations in glue-on AdS$_3$.
- Isaac Layton (University College London)
- "The quantum-quantum to classical-quantum limit"
[Abstract]
Abstract
We consider two interacting quantum systems and take the limit where one system remains quantum while the other is treated classically. This gives an effective theory in which a quantum system interacts with another system that exhibits classical behaviour. The resulting dynamics has a number of advantages over previous proposals, such as the semi-classical Einstein equations: (1) the semi-classical evolution is linear and valid for arbitrary superpositions of the quantum system; (2) the evolution includes the effect of back-reaction and quantum fluctuations on the classical system; (3) the size of these fluctuations determine the strength of decoherence on the quantum system. When the strength of quantum fluctuations is taken to be zero, our semi-classical limit recovers the standard classical limit. An interesting feature of this dynamics is that the quantum state remains pure at all times, conditioned on the effective classical evolution. We expect semi-classical limits of this kind to be important in studying the back-reaction of quantum fields on a classical spacetime in the context of inflation and black hole evaporation.
- Pompey Leung (University of British Columbia)
- "Horizons and Holographic Screen Sequestration" [pdf]
- Reishi Maeta (Hiroshima University)
- "2D gravity, matrix model, and JT gravity"
- Weibo Mao (Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences)
- "Local operator quench and inhomogeneous time evolution"
[Abstract] [pdf]
Abstract
We studied the non-equilibrium processes in two-dimensional conformal field theories due to the growth of operators induced by inhomogeneous and homogeneous Hamiltonians by investigating the time dependence of entanglement entropy and energy density. When we change the time order of the unitary evolution and regularization process, we studied how this change of time order affects the dynamical processes.
Consequently, we found that if we regulate the state after the operator grows with time, the time dependence of these quantities exhibits behaviors that have not been found so far.
Furthermore, we explored the gravity duals of the systems considered.
In this talk, I will report the details of these results.
- Shoichiro Miyashita (National Dong Hwa University)
- "Thermodynamics of Einstein-Maxwell system in a box"
[Abstract]
Abstract
At first sight, thermodynamical properties of gravity with asymptotically AdS condition and
ones with box boundary condition are similar. In pure gravity system, both exhibit a similar phase structure, that is, Hawking-Page phase transition occurs. However, when we include Maxwell field in the system, some discrepancies in thermodynamical properties between two cases were reported(JHEP 11 (2016) 041). Especially, their result indicates that thermodynamics of Einstein-Maxwell system in a box is in some sense ill-defined.
In this work, I propose a resolution of the problem of this ill-definedness by considering the contributions of the class of Euclidean geometries whose area of a bolt is larger than that of the boundary. Although one may feel strange because their Lorentzian continuations do not describe the exterior of Reissner-Nordstrom BH but a part of the interior of the inner horizon, the partition function and thermodynamics of the system turn out to be well-defined due to their contributions.
- Souparna Nath (Tata Institute of Fundamental Research, Mumbai)
- "The free energy of the large-N fermionic Chern-Simons theory in the 'temporal' gauge"
[Abstract]
Abstract
Most of the concrete evidence in support of the conjectured duality between Fermions coupled to U(N) Chern Simons theories, and Bosons coupled to level rank dual Chern Simons theories in 3 dimension has been obtained from large N computations performed in the 'lightcone' gauge.
In this paper we compute the thermal free energy for regular and critical bosons coupled to U(N) Chern Simons theory in the 'temporal' gauge (\partial_3 A_3 = 0). A key technical step in our computation is the consistent regulation of an unusual and highly divergent gauge determinant. Our final results are in perfect agreement with computations performed in the 'lightcone' gauge, providing a consistency check of earlier results, and potentially opening the door to new computations, for instance the computation of the thermal free energy on an arbitrary genus-g Riemann surface.
This work is done in collaboration with Shiraz Minwalla, Nikhil Tanwar and Vatsal
- Masato Nozawa (Osaka Institute of Technology)
- "C-metric wormholes"
[Abstract]
Abstract
We present a new family of AdS C-metric solutions in Einstein-phanton scalar system. The global causal structure is discussed in detail.
- Chintan Ashokkumar Patel (Tata Institute of Fundamental Research)
- "3 dimensional Bose-Fermi dualities in non-relativistic limit"
[Abstract]
Abstract
We find a non-relativistic description of matter Chern Simons theories on a sphere. We argue that the $n$ particle Hamiltonian is the Laplacian for $n$ particles moving on a sphere in the background of a ‘Knizhnik–Zamolodchikov' gauge field. We argue that the inner product on the $n$ particle Hilbert space is given in terms of the inner product on the space of conformal blocks. Using the pairing of conformal blocks under level-rank duality, we find a dual description of the $n$ particle wavefuntion which is that of $n$ particles coupled to the level-rank dual Chern Simons gauge boson. When all the particles are in fundamental or antifundamental representation, we demonstrate that the parity of the wavefunction changes under this duality, which clearly is a demonstration of the Bose-Fermi duality.
- Wyatt Reeves (University of British Columbia)
- "Symmetries and spectral statistics in chaotic conformal field theories"
[Abstract]
Abstract
We discuss spectral correlations in coarse-grained chaotic two-dimensional CFTs with large central charge. We study a partition function describing the dense part of the spectrum of primary states in a way that disentangles the chaotic properties of the spectrum from those which are a consequence of Virasoro symmetry and modular invariance. We argue that random matrix universality in the near-extremal limit is an independent feature of each spin sector separately; this is a non-trivial statement because the exact spectrum is fully determined by only the spectrum of spin zero primaries and those of a single non-zero spin (“spectral determinacy”). We then describe an argument analogous to the one leading to Cardy’s formula for the averaged density of states, but in our case applying it to spectral correlations: assuming statistical universalities in the near-extremal spectrum in all spin sectors, we find similar random matrix universality in a large spin regime far from extremality.
Based on arXiv:2302.14482 [hep-th] with Felix M. Haehl, Charles Marteau, and Moshe Rozali.
- Alan Rios Fukelman (King's College London)
- "From Group Theory to Spheres: Novel Features of Quantum Fields in dS"
[Abstract]
Abstract
In this talk we review some recent developments on the free field realization of the Gravitino in pure de Sitter spacetimes. We comment on the connection with the unitary irreducible representations of SO(1,d+1) and discuss the Harish-Chandra character as well as the 1-loop sphere path integral computation that allows us to compute corrections to the Gibbons-Hawking entropy of dS. Based on upcoming work with G. Silva, M. Sempe and D. Anninos.
- Francesco Sartini (Okinawa Institute of Science and Technology)
- "Hidden symmetries in cosmology and black holes"
[Abstract]
Abstract
Cosmological models and black holes belong to classes of space-time metrics defined in terms of a finite number of degrees of freedom, for which the Einstein–Hilbert action reduces to a one-dimensional mechanical model. We investigate their classical symmetries and the algebra of the corresponding Noether charges. These dynamical symmetries have a geometric interpretation, not in terms of spacetime geometry, but in terms of motion on the field space. Moreover, they interplay with the fiducial scales, introduced to regulate the homogeneous model, suggesting a relationship with the boundary symmetries of the full theory.
Finally, the existence of these symmetries unravels new aspects of the physics of black holes and cosmology. It opens the way towards a rigorous group quantization of the reduced models, to the study of their holographic properties. It might have significant consequences on the propagation of test fields and the corresponding perturbation theory.
- Yu-ki Suzuki (Yukawa Institute for Theoretical Physics, Kyoto University)
- "Information metric on the boundary"
[Abstract]
Abstract
The information metric on the space of boundary coupling constants in two-dimensional conformal field theories is studied. Such a metric is related to the Casimir energy difference of the theory defined on an interval. We concretely compute the information metric on the boundary conformal manifold of free boson CFT as well as SU(2)k WZW theory, obtaining the result expected from the symmetry of the systems. We also consider the holographic dual of the information metric.
- Vineeth Krishna Talasila (Tata Institute of Fundamental Research, Mumbai)
- "Supersymmetric Grey Galaxies and Revolving Black Holes"
[Abstract]
Abstract
In this presentation, I will talk about measures of multi-partite entanglement with the aim of constructing measures that can be computed in probe approximation in AdS/CFT. I will classify and count general measures as invariants of local unitary transformations. After formulating these measures in terms of permutation group elements, I will derive conditions that a probe measure should satisfy and find that a large class of solutions exist. Further, their holographic duals are computed with the assumption that the replica symmetry is unbroken in the bulk and give a check of this prescription with explicit computations in 2d CFTs. In the end, I will comment on the replica symmetry assumption and also how the already known entanglement measures, such as entanglement negativity and reflected entropy fit in this framework. Based on the work arXiv:2304.06082.
- Nikhil Tanwar (Tata Institute of Fundamental Research, Mumbai)
- "The free energy of the large-N fermionic Chern-Simons theory in the 'temporal' gauge"
[Abstract]
Abstract
There is now considerable evidence in support of the conjectured duality between fermions coupled to U(N) Chern-Simons theories, and Bosons coupled to level rank dual Chern-Simons theories in 3 dimension. Much of the concrete computational evidence for this conjecture comes from explicit computations in the large $N$ limit, almost all of which have, so far, been performed in lightcone gauge. In this paper we follow [arXiv:1410.0558] to compute the thermal free energy for regular and critical fermions coupled to $U(N)$ Chern-Simons theory in the `temporal' $\partial_3 A_3=0$ gauge.
Our final results are in perfect agreement with computations performed in the lightcone gauge, providing a consistency check of earlier results, and potentially opening the door to new computations, for instance the computation of the thermal free energy on an arbitrary Reimann surface.
This work is done in collaboration with Shiraz Minwalla, Souparna Nath and Vatsal.
- Kenya Tasuki (Yukawa Institute for Theoretical Physics, Kyoto University)
- "Evolution of Pseudo Entropy under Local Quenches"
[Abstract]
Abstract
We investigate the behavior of pseudo entropy, a generalization of entanglement entropy that depends on two quantum states, under local quantum quenches in two-dimensional conformal field theories (CFTs). We calculate the time evolution of pseudo entropy using conformal map methods and holographic analysis, respectively. Our investigation focuses on examining whether pseudo entropy exhibits enhancement compared to ordinary entanglement entropy. This presentation is based on our ongoing collaborative work with Kotaro Shinmyo and Tadashi Takayanagi.
- Bilyana Lyudmilova Tomova (Departement of Appied Mathematics and Theoretical Physics University of Cambridge)
- "Phase Space Renormalization and Finite BMS Charges in Six Dimensions"
[Abstract]
Abstract
We perform a complete and systematic analysis of the solution space of six-dimensional Einstein gravity. We show that a particular subclass of solutions -- those that are analytic near null infinity -- admit a non-trivial action of the generalized Bondi-Metzner-van der Burg-Sachs (GBMS) group which contains infinite-dimensional supertranslations and superrotations. The latter consists of all smooth volume-preserving Diff x Weyl. Using the covariant phase space formalism and a new technique (phase space renormalization), we are able to renormalize the symplectic potential using counterterms which are local and covariant. We then construct charges which faithfully represent the GBMS algebra and in doing so, settle a long-standing open question regarding the existence of GBMS symmetries in higher dimensional non-linear gravity. Finally, we show that the semi-classical Ward identities for the supertranslations and superrotations are precisely the leading and subleading soft-graviton theorems respectively.
- Takashi Tsuda (Yukawa Institute for Theoretical Physics, Kyoto University)
- "Multi-entropy in 2-dimensional CFT"
- Niloofar Vardian (International School for advanced study (Scuola Internazionale Superiore di Studi Avanzati))
- "Entanglement Renormalization of the class of Continuous Matrix Product States"
[Abstract]
Abstract
Continuous tensor network gives a variational ansatz for the ground state of the quantum field theories (QFTs). The notable examples are the continuous matrix product state (cMPS) and the continuous multiscale entanglement renormalization ansatz (cMERA). While cMPS is just adapted to the non-relativistic QFTs, only the Gaussian cMERA is well-understood which we can not use to approximate the ground state of the interacting relativistic QFTs. But instead, cMERA also corresponds to a real-space renormalization group flow in the context of the wave functions. In this talk, we investigate the backward Gaussian cMERA renormalization group flow of the class of cMPS by putting the standard cMPS at the IR scale. At the UV scale, for the bosonic systems in the thermodynamic limit, we achieve the variational class of states that has been proposed recently as the relativistic cMPS (RCMPS) is adapted to the relativistic QFTs without requiring to introduce of any additional IR or UV cut-off. We also extend the RCMPS to fermionic systems and theories on a finite circle.
- Dorin Weissman (Asia Pacific Center for Theoretical Physics)
- "Chaotic behavior of string scattering amplitudes"
[Abstract]
Abstract
Scattering of highly excited string (HES) states offers a unique opportunity to study chaotic dynamics in quatum scattering amplitudes. We present three- and four-point scattering amplitudes involving one HES state. These amplitudes can be computed exactly at tree level using the DDF formalism, and have compact analytic forms. We show that they are chaotic, in the sense that the spacings between successive peaks in the angular dependence of the amplitude have the same behavior as level spacings of chaotic Hamiltonian systems, i.e. they are distributed as predicted by random matrix theory.
Based on [Phys.Rev.Lett. 129 (2022) 26] and [hep-th/2303.17233]
- Qiang Wen (Shing-Tung Yau Center of Southeast University)
- "Island phase as a property of quantum state and Hilbert space"
[Abstract]
Abstract
I will give a purely quantum information perspective for the Island formula. In a quantum system when the state of a subset is totally encoded in the state of another subset, the Hilbert space of the system will reduce, and the way we compute the reduced density matrix and related entropy quantities will also change essentially. Such reductions of the Hilbert space result in a new island formula in quantum systems, which we conjecture to be the same island formula in gravity recently proposed to reproduce the Page curve. Furthermore, we propose a non-gravitational field theory configuration where entanglement islands emerge, give a description for the entanglement structure of the island phase.
- Yuki Yokokura (iTHEMS, RIKEN)
- "A Semi-classical Spacetime Region with Maximum Entropy"
[Abstract]
Abstract
For a spherical static spacetime with no trapped surface, we study the entropy of many semi-classical degrees of freedom taking into account the full self-gravity in the semi-classical Einstein equation. We consider typical behaviors of highly excited quanta to find an entropy upper bound fixed by the region size and the energy density. Then, the saturating condition determines the physical spacetime uniquely as a dense configuration with near-Planckian curvatures, and the maximum entropy agrees with the Bekenstein-Hawking formula exactly.
- Yu-Xuan Zhang (Jilin University)
- "Pseudo entropy under local operator quenches in two-dimensional conformal field theories"
[Abstract] [pdf]
Abstract
Pseudo entropy is a generalization of entanglement entropy that has recently been proposed via AdS/CFT correspondence and post-selection processes. It possesses a complex-valued nature and exhibits promising research and application prospects in holography, quantum field theory, quantum information, and quantum many-body physics. In this presentation, I will discuss the behavior of pseudo entropy under the local operator quenches in various two-dimensional conformal field theories. The local operators under consideration include primary operators, descendant operators, and their linear combinations. I will compare the similarities and differences between pseudo entropy and entanglement entropy and demonstrate the symmetry exhibited by pseudo entropy under specific configurations. Finally, I will discuss how these symmetries closely relate to pseudo-Hermiticity in non-Hermitian physics.
- Rana Zibakhsh (University of British Columbia)
- "Cosmology sourced by holographic matter in the quasi-static regime"
[Abstract]
Abstract
This study focuses on the application of holographic techniques to explore the equation of state governing relevant deformations of conformal field theories (CFTs) and their impact on cosmological dynamics by sourcing the stress tensor. By leveraging holographic duality, which connects quantum field theories to gravitational theories in higher-dimensional spacetimes, we aim to elucidate the behaviour of these theories within a cosmological context. Our investigation focuses on the effects of turning on relevant operators and their implications for the energy and pressure within the CFT. We parametrize a class of quantum field theories at various temperatures by utilizing holographic renormalization techniques and analyze the corresponding thermodynamic equation of state governing the evolution of the scale factor in cosmological scenarios The outcomes of this research have the potential to advance our understanding of the overlap between holography and cosmology while offering valuable implications for studying inflationary models in the presence of strongly interacting quantum fields.