Program
2024/06/28 15:37 updated
Schedule
7/1 (Monday)
(Chair: Nozaki)
10:30-11:30 Masataka Watanabe
11:30-13:00 Lunch
13:00-14:00 Shan-Ming Ruan
14:00-15:00 Song He
15:00-16:00 Tokiro Numasawa
16:00-17:00 Xuanhua Wang
7/2 (Tuesday)
(Chair: Tamaoka)
10:30-11:30 Keiju Murata
11:30-13:00 Lunch
13:00-14:00 Chushun Tian
14:00-15:00 Mitsuhiro Nishida
15:00-16:00 Sotaro Sugishita
16:00-17:00 Free discussion
7/3 (Wednesday)
(Chair: Wang)
10:30-11:30 Bartek Czech
11:30-13:00 Lunch
13:00-14:00 Pengfei Zhang
14:00-15:00 Masazumi Honda
15:00-16:00 Pratik Nandy
16:00-17:00 Tomonori Ugajin
7/4 (Thursday)
(Chair: Watanabe)
10:30-11:30 Kotaro Tamaoka
11:30-13:00 Lunch
13:00-14:00 Yiming Chen
14:00-15:00 Akihiro Miyata
15:00-16:00 Wei Song
16:00-17:00 Free discussion
7/5 (Friday)
(Chair: Miyata)
10:30-11:30 Jinzhao Wang
11:30-13:00 Lunch
13:00-14:00 Masamichi Miyaji
14:00-15:00 Ling-Yan Hung
15:00-16:00 Kanato Goto
16:00-17:00 Free discussion
7/1 (Monday)
10:30-11:30
Speaker: Masataka Watanabe
Title: Physics of the Split Property
Abstract: I will give a concrete physical procedure which obtains the intermediate Type I factor of von Neumann algebras of quantum field theories, used in defining the reduced density matrix and in computing the entanglement entropy.
11:30-13:00 Lunch
13:00-14:00
Speaker: Shan-Ming Ruan
Title: A Half de Sitter Holography
Abstract: To explore de Sitter holography, we consider a half dS spacetime in which a time-like boundary encloses the bulk spacetime. By analyzing the holographic entanglement entropy in this space, we argue that gravity on a half dS_{d+1} is dual to a highly non-local field theory residing on the dS_d boundary. This non-locality illustrates the violation of the subadditivity of the holographic entanglement entropy. To probe the half de Sitter space, we glue it with a non-gravitational bath spacetime. However, we show that the quantum extremal surface is generally absent in this situation due to the fact that the island anchored on de Sitter space cannot dominate. By applying double holography, we further illustrate that the island should be smeared over de Sitter space and the entanglement wedge will include whole de Sitter gravity region.
14:00-15:00
Speaker: Song He
Title: Holographic correlators on higher genus Riemann surface with/without TTbar
Abstract: In this work, we present a comprehensive study of holographic stress tensor correlators on general Riemann surfaces, extending beyond the previously well-studied torus cases to explore higher genus conformal field theories (CFTs) within the framework of the Anti-de Sitter/conformal field theory (AdS/CFT) correspondence. We develop a methodological approach to compute holographic stress tensor correlators, employing the Schottky uniformization technique to address the handlebody solutions for higher genus Riemann surfaces. {Through rigorous calculations, we derive four-point stress tensor correlators,} alongside recurrence relations for higher-point correlators, within the AdS3/CFT2 context. Additionally, our research delves into the holography of cutoff AdS3 spaces, offering novel insights into the lower-point correlators of the TTbar-deformed theories on higher genus Riemann surfaces up to the first deformation order.
15:00-16:00
Speaker: Tokiro Numasawa
Title: Gauging spacetime Inversions in quantum gravity
Abstract: Spacetime inversion symmetries such as parity and time reversal play a central role in physics, but they are usually treated
as global symmetries. In quantum gravity there are no global symmetries, so any spacetime inversion symmetries must be gauge symmetries.
In particular this includes CRT symmetry (in even dimensions usually combined with a rotation to become CPT), which in quantum field theory is always a symmetry and seems likely to be a symmetry of quantum gravity as well. In this talk, we will discuss what it means to gauge a spacetime inversion symmetry and explain some of the more unusual consequences of doing this. In particular, I will argue that the gauging of CRT is automatically implemented by the sum over topologies in the Euclidean gravity path integral, that in a closed universe the Hilbert space of quantum gravity must be a real vector space, and that in Lorentzian signature manifolds which are not time-orientable must be included as valid configurations of the theory.
16:00-17:00
Speaker: Xuanhua Wang
Title: Page time as transition of information channels
Abstract: In the holographic code space, the dynamics of a black hole is unitary. Information recovery is guaranteed and the corresponding decoding methods were proposed based on this assumption. In the effective field theory picture involving Hawking pair production, redundant modes are annihilated in final-state-projection models and the viability of information recovery is no longer guaranteed. This talk will be focused on the information recoverability based on the final-state projection and non-isometric mapping proposals and show the emergence of Page time as a transition of information channels in this setup.
7/2 (Tuesday)
10:30-11:30
Speaker: Keiju Murata
Title: Observing black holes through AdS/CFT
Abstract: The AdS/CFT correspondence predicts that the thermal states of certain field theories correspond to black holes in asymptotically AdS spacetime. Can we observe "black hole-like" phenomena of through thermal states of realistic systems? In this talk, I will discuss examples of methods to achieve this, including the measurement of Einstein rings produced by AdS black holes and the creation of geodesics in AdS spacetime. These measurements of "black hole-like" phenomena would be used to test whether the underlying description of a given material involves a black hole.
11:30-13:00 Lunch
13:00-14:00
Speaker: Chushun Tian
Title: Quantum Hall physics in skew-product dynamical systems
Abstract: Since the inception ofthe Kolmogorov-Arnold-Moser theorem, skew-product dynamical systems play vital roles in the development of modern dynamical system theory. In this talk, I shall discuss how a special class of such classical dynamical systems, i.e. the skew productsover $\mathbb{T}^2\times SU(2)$, may allow one to explore quantum Hall physics. In particular, I shall show how the quantum Hall transition is translated into the transition in the stability of classical trajectories in phase space in skew-product systems.
14:00-15:00
Speaker: Mitsuhiro Nishida
Title: Krylov complexity as an order parameter for deconfinement phase transitions at large $N$
Abstract: Krylov complexity has been proposed as a diagnostic of chaos in non-integrable lattice and quantum mechanical systems, and if the system is chaotic, Krylov complexity grows exponentially with time. However, when Krylov complexity is applied to quantum field theories, even in free theory, it grows exponentially with time. This exponential growth in free theory is simply due to continuous momentum in non-compact space and has nothing to do with the mass spectrum of theories. Thus by compactifying space sufficiently, exponential growth of Krylov complexity due to continuous momentum can be avoided. In this paper, we propose that the Krylov complexity of operators such as $\mathcal{O}=\Tr[F_{\mu\nu}F^{\mu\nu}]$ can be an order parameter of confinement/deconfinement transitions in large $N$ quantum field theories on such a compactified space. We explicitly give a prescription of the compactification at finite temperature to distinguish the continuity of spectrum due to momentum and mass spectrum. We then calculate the Krylov complexity of $\mathcal{N}=4, 0$ $SU(N)$ Yang-Mills theories in the large $N$ limit by using holographic analysis of the spectrum and show that the behavior of Krylov complexity reflects the confinement/deconfinement phase transitions through the continuity of mass spectrum.
15:00-16:00
Speaker: Sotaro Sugishita
Title: Subregion Complementarity in AdS/CFT
Abstract: We examine the bulk reconstruction in the AdS/CFT correspondence. We point out the problems in the causal wedge reconstruction and argue that the subregion duality fails to hold. Nevertheless, we propose the subregion complementarity, illustrating that different CFT operators can describe a bulk subregion. While we expect that this complementarity is valid outside the horizon in general eternal black holes, it is inapplicable for single-sided black holes where a semi-classical description at the stretched horizon is absent.
16:00-17:00 Free discussion
7/3 (Wednesday)
10:30-11:30
Speaker: Bartek Czech
Title: Everything Everywhere All at Once: Holographic Entropy Inequalities, the Topology of Error Correction, Black Holes, Cubohemioctahedron, and (maybe) the Toric Code
Abstract: An important class of quantum states are those whose entanglement entropies can be computed by minimal cuts through some bulk structure---a holographic spacetime or a random tensor network. Such states obey linear constraints on their entanglement entropies, which are known as holographic entropy inequalities. I present two new infinite families of holographic entropy inequalities. The entropies featured in these inequalities are best visualized on graphs whose incidence relations reflect subsystem inclusion. These graphs turn out to be tessellations of the torus and the projective plane. The non-contractible cycles on these manifolds play an indispensable role in proving the inequalities, which shows that they hold for essentially topological reasons. Physically, the inequalities suggest a novel, topological aspect of holographic error correcting codes; they also characterize the entropy of two-sided black holes. If time allows it, I will sketch bonus applications, which involve a non-planar polytope called "cubohemioctahedron" and (more speculatively) the toric code.
11:30-13:00 Lunch
13:00-14:00
Speaker: Pengfei Zhang
Title: Operator size dynamics: theory and application
Abstract: In closed many-body systems, initially localized quantum information spreads throughout the entire system, a phenomenon known as information scrambling. This is typically quantified by the growth in operator size. After introducing the concept of operator size growth in both closed and open systems, we discuss how studying this growth can advance quantum science and technology. Specifically, we provide examples related to quantum neural networks and state tomography. In both cases, understanding operator size dynamics offers a novel perspective for realizing algorithms with higher expressivity or efficiency. We also discuss the implications of dynamical transitions in operator size for many-body quantum teleportation.
14:00-15:00
Speaker: Masazumi Honda
Title: Jackiw-Teitelboim gravity with matter on quantum computer
Abstract: Recently there is much attention to a (1+1) dimensional gravity called Jackiw-Teitelboim (JT) gravity in various contexts such as holography, black hole and wormhole. When JT gravity is coupled to matter, it becomes much harder to handle the theory analytically. Furthermore, it is expected that the conventional numerical approach by Monte Carlo method is not practically applicable to simulate real time dynamics due to infamous sign problem. In my talk, I will discuss how to simulate JT gravity with matter by quantum computer. This talk is based on a joint work in progress with Rumi Hasegawa.
15:00-16:00
Speaker: Pratik Nandy
Title: An Operator growth hypothesis for open quantum systems
Abstract: Under the Hamiltonian evolution, a simple operator turns into a complicated operator. The growth of such an operator is drastically different when the system is connected to a dissipative environment than in a typical closed system. We probe such growth via a recently explored measure of scrambling known as Krylov complexity and aim to propose an operator growth hypothesis in open quantum systems. We review the current progress and challenges of applying this approach to open systems and illustrate some examples from the dissipative SYK model.
16:00-17:00
Speaker: Tomonori Ugajin
Title: Double Holography of Entangled Universes
Abstract: We employ double holography to examine a system of two entangled gravitating universes that live on two codimension-one branes in an asymptotically AdS3 spacetime with two disjoint conformal boundaries. There are distinct brane configurations depending on the temperature of the thermofield double (TFD) state between the left and right systems. The topology transition between two branes is naturally identified with the emergence of an Einstein-Rosen bridge connecting the two entangled universes. This doubly holographic construction offers a holographic perspective on gravitational collapse and black hole formation in brane universes. Through this holographic framework, we analyze the quantum information structure of the two gravitating universes. Specifically, we calculate the mutual information between defects present in the boundary theories on the left and right sides. Furthermore, we investigate the decoupling process in the Hayden-Preskill protocol applied to the two copies of the defect field theory and discuss the interpretation of the Yoshida-Kitaev decoding protocol.
7/4 (Thursday)
10:30-11:30
Speaker: Kotaro Tamaoka
Title: Black Hole Singularity and Timelike Entanglement
Abstract: We study timelike and conventional entanglement entropy as potential probes of black hole singularities via the AdS/CFT correspondence. Using an analytically tractable example, we find characteristic behavior of holographic timelike entanglement entropy when the geometry involves a curvature singularity. We also observe interesting phenomena that, in some particular setups, holographic timelike and conventional entanglement entropy are determined from multiple complex saddle points, which fall outside the assumptions of the Lewkowycz-Maldacena type argument.
11:30-13:00 Lunch
13:00-14:00
Speaker: Yiming Chen
Title: Chaos and BPS states
Abstract: In this talk, I will review a prescription to generalize the notion of quantum chaos to BPS states in supersymmetric theories, first discussed by Lin-Maldacena-Rozenberg-Shan. Using their prescription, we examine whether various BPS sectors in \mathcal{N}=4 SU(N) SYM exhibit chaos. Through explicit computations at weak coupling in the gauge theory, we show that the BPS sectors are non-chaotic when they are dual to horizonless geometries in the bulk. On the other hand, for the 1/16-BPS sector which is dual to macroscopic black holes, I will argue for the existence of chaos based on recent insights on the fortuity phenomenon in this sector. The talk will be based on upcoming work with Henry Lin and Stephen Shenker.
14:00-15:00
Speaker: Akihiro Miyata
Title: Black hole states in non-gravitating and non-gravitating baths
Abstract: We study the distinguishability between black hole states with non-gravitating and gravitating baths in the PSSY model and the doubled PSSY model. By checking the entanglement entropies of black holes in their cases, one can see that the leading results are the same, but the sub-leading results are different due to a difference in partially-connected replica saddles. We qualitatively investigate the difference between them using relative entropy. In this talk, I will explain the behavior of the relative entropy and its possible interpretation.
15:00-16:00
Speaker: Wei Song
Title: Asymptotic symmetries from the string worldsheet
Abstract: Symmetry has been a guiding principle in modern theoretical physics. In particular, the study of asymptotic symmetry is very useful in setting up holographic dualities in the bottom-up approach. In this talk, we will discuss asymptotic symmetries in a top-down approach, from worldsheet string theory.
We will study several examples including string theory on the backgrounds of AdS3 with NS-NS flux, flat spacetime, and the TsT/TTbar correspondence.
16:00-17:00 Free discussion
7/5 (Friday)
10:30-11:30
Speaker: Jinzhao Wang
Title: Quantum Energy Teleportation versus Information Teleportation
Abstract: Quantum energy teleportation (QET) is the phenomenon in which locally inaccessible energy is activated as extractable work through collaborative local operations and classical communication (LOCC) with an entangled partner. It closely resembles the more well-known quantum information teleportation (QIT) where quantum information can be sent through an entangled pair with LOCC. It is tempting to ask how QET is related to QIT. Here we report a first study of this connection. Despite the apparent similarity, we show that these two phenomena are not only distinct but moreover are mutually exclusive to each other. We show a perturbative trade-off relation between their performance in a thermal entangled chaotic many-body system, in which both QET and QIT are simultaneously implemented through a traversable wormhole in an emergent spacetime. To better understand their competition, we study the finite-dimensional counterpart of two entangled qudits and prove a universal non-perturbative trade-off bound. It shows that for any teleportation scheme, the overall performance of QET and QIT together is constrained by the amount of the entanglement resource. (Based on the joint work https://arxiv.org/abs/2405.13886 with Shunyu Yao)
11:30-13:00 Lunch
13:00-14:00
Speaker: Masamichi Miyaji
Title: Codimension-Zero Observables at Late Time
Abstract: Classically, the volume of the Einstein-Rosen bridge of the two-sided black hole grows linearly in time. Such linear increase is in conflict with the finite black hole entropy S, thus at late time, the volume should be upper-bounded and saturate at the time scale O(e^S). The bulk mechanism of such saturation is due to the production of baby universes which shorten the ER bridge. In this talk, we construct a family of codimension-zero observables non-perturbatively that probe the quantum properties of the ER bridge at late time. This construction allows us, for example, to study the late-time behavior of the Wheeler-de-Witte action which is conjectured to be dual to the state complexity. The new important element in the codimension-zero observables is the presence of "operator wormholes," which are the baby universes emanating from the codimension-zero region. We find that along with the bra-ket wormholes that shorten the ER bridge, these operator wormholes have a significant impact on the late-time behavior of the codimension-zero observables.
14:00-15:00
Speaker: Ling-Yan Hung
Title: Building Up Quantum Spacetimes with BCFT Legos
Abstract: Is it possible to read off the quantum gravity dual of a CFT directly from its operator algebra? In this talk, I will present a step-by-step recipe for building up 3D quantum spacetimes dual to 2D CFTs, synthesizing results and techniques from conformal bootstrap, topological symmetries, real-space tensor network renormalization, and the asymptotics of quantum 6j symbols. Quantum Liouville theory serves as a simple and explicit example, illustrating how the exact CFT/gravitational path integral can be built up from triangulation and local pieces of BCFT correlation functions, which we call the ``BCFT Legos''. This is essentially a tensor network that admits an interpretation of a state-sum of a 3D topological theory constructed with quantum 6j symbols of Uq(SL(2,R)) with non-trivial boundary conditions, and it reduces to a sum over 3D geometries weighted by the Einstein-Hilbert action to leading order in large c. The triangulation coincides with producing a network of geodesics in the AdS bulk, which can be changed making use of the pentagon identity and orthogonality condition satisfied by the 6j symbols, and arranged into a precise holographic tensor network. The constructive map between gravity and CFT naturally and explicitly bridges local geometrical data, algebraic structures, and quantum entanglement.
15:00-16:00
Speaker: Kanato Goto
Title: Holography of Subregion Algebra
Abstract: Quantum field theories (QFTs) have played a pivotal role in describing minuscule realms that constitute our world over the past century. Nonetheless, local QFTs, which allow quantum fluctuations infinitely small regions, have consistently wrestled with infinite quantities and the complexity of their mathematical structure. In particular, a QFT has an uncountably infinite amount of entanglement near the boundary of a local region, preventing the introduction of the finite, mathematically tractable notion of von Neumann entropies. This is manifested in the fact that the algebras of a QFT in a local region is classified as Type III, which is the most mathematically challenging type of von Neumann algebra.
The AdS/CFT correspondence typically establishes a profound connection between quantum gravity on anti-de Sitter (AdS) spacetime and a non-gravitational local QFT, specifically a conformal field theory (CFT), on the spacetime boundary placed at "infinity" of AdS. The Ryu-Takayanagi formula for holographic entanglement entropy in AdS/CFT manifests the importance of a CFT in a local region for understanding quantum gravity. Ultraviolet divergence of entanglement entropy in CFT (and its holographic dual) reflects that the von Neumann algebras of a CFT in a subregion are Type III. Usually, when computing the entanglement entropy, one introduces a UV cutoff (or IR cutoff of the dual spacetime) by hand, making the entanglement entropy a finite quantity with cutoff dependence. However, this drastically breaks the local (and causal) properties that QFT originally had.
In this talk, I will propose how to obtain the Type II subregion algebras by modifying the original CFT using a natural prescription under the AdS/CFT correspondence without violating the causality that the original local CFT has. I will explain in detail why this prescription yields Type II algebras, using an example of two-dimensional CFTs. We then generalize the recent argument of Witten et al. and derive the Ryu-Takayanagi formula from the operator algebras.
16:00-17:00 Free discussion