# Poster Presentations

#### Ali Akil (University of Hong Kong):

**Coherent Entanglement Swapping in a Superposition of Black Hole Evaporations**

We revisit Hawking’s black hole evaporation process, allowing the black hole mass to be a quantum variable. We adopt a minimalistic approach, where the complications of the geometry are reduced to a mass-dependent horizon, the black hole matter is in a general, possibly entangled quantum state, and the Hawking radiation pairs are in a quantum superposition of the allowed energies. The particles created inside the black hole are assumed to annihilate with the black hole matter. Since the Hawking particles have an undetermined energy, the black hole gets in a superposition of being fully evaporated and not fully evaporated. We show, under natural assumptions, that in the branch of the superposition where the matter is annihilated to vacuum, the outgoing Hawking particles encode the initial state of the black hole matter. In the branch of the superposition where the black hole matter is not fully annihilated, more pairs continue to be created. We model this branch- dependent pair creation with controlled unitaries. With every burst of radiation the probability of the full annihilation strictly increases. As the number of bursts tends to infinity, the black hole is fully evaporated and its initial state is swapped to the outside particles in every branch of the quantum superposition. This repeated controlled operation accounts for the back-reaction of every burst of radiation on the black hole state. (In collaboration with Caslav BRUKNER, Giulio CHIRIBELLA, Oscar DAHLSTEN, Lorenzo GIANNELLI, and Leonardo MODESTO.)

#### Goncalo Araujo Regado (OIST):

**Could the Hilbert space of quantum gravity be trivial?**

In this talk I will discuss a conceptual paradox that emerges when we take the holographic principle seriously. If the universe has a closed spatial topology, then the holographic dual theory can only encode a unique global state of the universe. However, the experience of an observer in the universe suggests that their surroundings could be in many possible states. How do we reconcile this rich semiclassical physics with a potentially trivial Hilbert space for the universe as a whole? This points at the very intricate way in which information is encoded in quantum gravity.

#### Chen Bai (Kavli Institue for Theoretical Sciences):

**The dynamics of inhomogeneous time evolution in 2d CFTs**

TBD

#### Chiara Baracco (King's College London):

**2D Quantum Cosmology**

We consider two-dimensional quantum gravity with a positive cosmological constant coupled to a conformal field theory of large and positive central charge. Building on previous work, we study the cosmological properties of this model at the quantum level. We provide a complete ADM analysis of the classical phase space, revealing a discretuum of either bouncing or big bang/crunch type cosmologies. At the quantum level, one can solve the Wheeler-DeWitt equation exactly. In the semiclassical limit, the Wheeler-DeWitt state space is linked to the classical phase space. Wavefunctionals of the Hartle-Hawking and Vilenkin type are identified, and a quantum version of the bouncing spacetime is found. We retrieve the Hartle-Hawking wavefunction from a disk path integral of timelike Liouville theory. To do so, we must select a particular contour in the space of complexified fields. The quantum information content of the big bang cosmology is considered, and contrasted to the de Sitter horizon entropy as computed by a gravitational path integral over the two-sphere.

#### Jaydeep Kumar Basak (National Sun Yat Sen University, Taiwan):

**Timelike Entanglement Entropy and Constraints in Non-relativistic Anisotropic Theories**

I will discuss the behavior of timelike entanglement entropy (TEE) for holographic theories with general dynamical critical exponent $z$ and hyperscaling violation exponent $\theta$. Here TEE receives contributions from a set of spacelike surfaces and a finite timelike bulk surface with mirror symmetry. Utilizing various conditions on these surfaces in UV and IR regions, I will obtain basic constraints on $z$ and $\theta$. I will show that the parameter space confined by these constraints is a portion of the parameter space restricted by the null energy conditions and the stability condition.

#### Juan Pablo Bayona Pena (YITP, Kyoto)

**Entanglement Spectrum Dynamics as a Probe for Non-Hermitian Bulk-Boundary Correspondence in Periodic Systems**

In recent years, the investigation of non-Hermitian or open quantum systems has uncovered a remarkable phenomenon

known as the non-Hermitian (Liouvillian) skin effect, where the system exhibits spectral sensitivity to boundary conditions. This effect challenges conventional notions of Hermitian topological phases, where the presence of symmetry-protected edge states is typically inferred from properties of the Bloch Hamiltonian (bulk-boundary correspondence). Instead, in open quantum systems exhibiting the Liouvillian skin effect, redefining topological invariants in terms of the open boundary Hamiltonian becomes necessary (non-Hermitian bulk-boundary correspondence). In this study, we tackle the query: Can a topological transition in open boundary conditions be observed in a system with periodic boundary conditions? We affirmatively respond to this question. We show that the time evolution of the entanglement spectrum of a quenched periodic open quantum fermionic system serves as a dynamic probe for detecting non-Hermitian bulk-boundary correspondence. In particular, we demonstrate that the entanglement spectrum exhibits a zero-crossing only when the system is quenched from a topologically trivial to non-trivial phase defined from the spectrum in open boundary conditions, even in systems featuring the Liouvillian skin effect. Our results reveal that non-Hermitian topological phases leave a

distinctive imprint on the unconditional dynamics within a subregion of systems subject to dissipation.

#### Jordan Docter (Stanford University):

**Pseudorandom Unitaries from Random Matrix Sums**

Random unitaries are highly useful in quantum algorithms, with diverse applications to benchmarking, tomography, and communication. However, random unitaries are exponentially difficult to produce. The desire to spoof them efficiently in the past few decades has propelled the study of both statistical and computational notions of pseudorandom unitaries — constructions which are both “close” to Haar, and efficient to construct. We present new progress with respect to both notions of pseudorandomness: (i) A natural question is how efficiently one can produce unitary T-designs, the statistical notion of pseudorandom unitaries. The most efficient prior construction of unitary T-designs for n-qudit systems used O(T^5 n^2) quantum gates. In these works, we give new constructions of T-designs via random matrix sums which use merely O(T poly(n)) quantum gates, which yields optimal scaling in T. (ii) The notion of a computational pseudorandom unitary was proposed recently, but not shown to exist. In this work, we also provide the first construction of non-adaptive computational pseudorandom unitaries. Our constructions derive from random matrix sums, in comparison to commonly studied local random circuits. A central feature of our proof is a new connection between the polynomial method in quantum query complexity and the large-dimension (N) expansion in random matrix theory. In particular, we show that the polynomial method provides exponentially improved bounds on the high moments of certain random matrix ensembles, without requiring intricate Weingarten calculations. Note: Michelle Xu and I would like to jointly present these works. We believe that the content is suitable for two adjacent slots. In addition to several exciting results regarding a long standing open problem in quantum information, we would present a number of new techniques in random matrix theory that would be applicable to many subfields. We would be willing to share one slot otherwise.

#### Samuel Fedida (CQIF, DAMTP, University of Cambridge):

**The mixture equivalence principle and post-quantum theories of gravity**

We examine the mixture equivalence principle, which states that proper and improper mixed states are experimentally indistinguishable. We point out that semiclassical gravity and, more generally, nonlinear extensions of quantum mechanics violate the mixture equivalence principle. We further demonstrate that nonlinear modifications to the Born rule in quantum theory generically violate this principle. We show that such violations may lead to theoretical inconsistencies when modelling thermal baths, for example in black hole physics. We show that either semiclassical gravity is inconsistent, or standard derivations of Hawking radiation are unsound within this theory. Hence quantum field theory in curved fixed spacetime is not a limiting theory of semiclassical gravity in the context of black holes with negligible gravitational back-reactions. We argue that violations of the mixture equivalence principle imply that some post-quantum theories do not reduce to effective field theories or are simply theoretically inconsistent.

#### Mohammed Akram Fellah (Department of Physics, Badji Mokhtar University, Annaba, Algeria):

**The island Formula and Replica Wormholes**

The subject of the talk revolves around one of the paradoxes that plague our understanding of the nature of black holes: The Information Loss Paradox. These paradoxes emerge when the late Hawking partially combined Quantum Mechanics and Gravity in the study of black holes. Among the results of Hawking’s work is that Black Holes evolution seem to induce information loss in the universe: evolution is not a unitary operation. Gauge/Gravity duality gives promising paradigm to tackle the Information Loss Paradox as it relates theories with gravity and hence black holes with gauge theories that we understand their quantization very well. There has been some progress in recent years on how to incorporate black Hole evaporation process in such a paradigm. This led to some insights on how information might be retrieved and unitarity restored. The talk will build on these findings and try to make the process of information recovery clearer by investigating the island formula and replica wormholes method.

#### Honami Fukushima (Department of Physics, College of Humanities and Sciences, Nihon University):

**Pseudo entanglement entropy as a probe of quantum phase transitions: Matrix product state approach**

The concept of entanglement entropy is currently at the forefront of various fields of physics, serving as a fundamental measure of quantum information stored in a quantum state, playing a crucial role in the condensed-matter physics for phase identification, and establishing a holographic relation to the gravitational theory. Recently, a quantity extending the von Neumann entanglement entropy, termed "pseudo entanglement entropy," has been introduced within the framework of the anti-de Sitter/conformal field theory (AdS/CFT) correspondence [1,2]. While the pseudo entanglement entropy is associated with the area of minimal surfaces in a time-dependent Euclidean space in AdS/CFT, its utility as an indicator to distinguish between the phases of two different quantum states in lattice models has been explored [2], albeit in relatively small systems. In this study, we investigate the behavior of pseudo entanglement entropy and its related concept, singular value decomposition (SVD) entanglement entropy [3], in phase transition phenomena on a large number of lattice sites. Developing a method based on the matrix product state representation to compute these quantities in large-size systems, we present their behavior across the quantum critical point of the Ising chain model with transverse and longitudinal fields. The comparison between cases where the reference two states are in the same phase and in different phases reveals distinctly different features in the thermodynamic limit. This provides a new perspective in characterizing distinct phases in quantum many-body systems and offers profound insights into the role of the pseudo (and SVD) entanglement entropy in holographic correspondence. [1]: Y. Nakata et al., Phys. Rev. D 103, 026005 (2021). [2]: A. Mollabashi et al., Phys. Rev. Lett. 126, 081601 (2021). [3]: A. Parzygnat et al., JHEP 12, 123 (2023).

#### Hideo Furugori (Kyoto University):

**On the Aharonov-Bohm Type Memory Effect**

It is known that memory effects in electromagnetism and general relativity are mathematically equivalent to the soft photon and graviton theorems in quantum field theory, which are associated with infrared divergent S-matrix elements. The dressed state formalism in quantum field theory, which incorporates the interaction of soft particles into asymptotic states, enables the definition of a divergence- free S-matrix. In this formalism, the soft theorem can be viewed as a certain approximation of the dressed states, suggesting that dressed states offer a better perspective for considering memory effects. In this presentation, I will discuss a new type of memory effect related to the Aharonov-Bohm effect.

#### Dongsheng Ge (Osaka University):

**TBD**

TBD

#### Jan Głowacki (University of Oxford):

**Towards Relational Quantum Field Theory**

In would like to speak about a newly developed relational approach to relativistic quantum physics steaming from the theory of operational quantum reference frames (QRFs). Considering the QRF framework in the context of Special Relativity by taking the Poincare group as the underlying symmetry structure provides a novel relational perspective on the notion of a quantum field. This perspective is then extended to curved geometries by replacing the Poincare group with a Lorentz bundle. The formalism is also capable of dealing with indefinite background geometries when formulated in the context of the frame bundles.

#### KABERI GOSWAMI (Chennai Mathematical Institute):

**Small Schwarzschild de Sitter black holes, the future boundary and islands**

In arxiv: 2312.05604 we have studied 4-dimensional Schwarzschild de Sitter black holes in the regime where the black hole mass is small compared with the de Sitter scale, following arXiv:2207.10724 [hep-th]. The de Sitter temperature is very low compared with that of the black hole. We consider the future boundary as the location where the black hole Hawking radiation is collected. Using 2-dimensional tools, we find unbounded growth of the entanglement entropy of radiation as the radiation region approaches the entire future boundary. Self-consistently including appropriate late time islands emerging just inside the black hole horizon leads to a reasonable Page curve. We also discuss other potential island solutions which show inconsistencies.

#### Ryuki Ito (Tokyo Institute of Technology):

**real-space renormalization for analysis of critical points in a permutation model on hierarchical lattice**

Quantum circuits are expected to efficiently solve problems that are difficult to handle with classical computers. Since it is difficult to experiment with large-scale quantum circuits due to noise effects, theoretical analysis becomes necessary. Recently, a permutation spin model has been attracting attention in the fields of quantum computation because of a correspondence between the entanglement entropy of Random quantum circuits and the free energy of a permutation spin model.A previous study estimated the phase transition point of mn-th permutation spin model on square lattice by using the duality analysis and found the phase transition point of the entanglement entropy of RQC by taking the limit as mn→0. However, since this result is a prediction, the exact phase transition point has not been found yet. In this study, we aim to find the phase transition point of the mn-th permutation spin model on hierarchical lattice using real-space renormalization. This method reveals the flow of the relative Boltzmann factor of the spin model, rather than the flow of coupling constants as typically done. As a result, we found the exact phase transition point of mn-th permutation spin models on hierarchical lattice for small mn, and this result agrees with the previous studies.

#### Krishna Jalan (The Institute of Mathematical Sciences, Chennai, India):

**Generalized Second Law for Non-minimally Coupled Matter Theories**

We prove the generalized second law (GSL) for higher curvature gravity theories when the matter sector is non-minimally coupled. The validity of our proof is in the regime of linearized fluctuations about equilibrium black holes. We describe how to generalize the proof of linearized semi-classical GSL when the matter sector comes with non-minimal couplings. The proof proceeds by suitably evaluating the matter path integral in the stress tensor expectation value by treating the higher derivative couplings in an effective field theory setting.

#### Takuma Kaise (Graduate School of Science and Technology, Niigata University):

**Numerical analysis of the angular-time evolution for the S=1 Heisenberg chain**

The ground states of low-dimensional quantum many-body systems exhibit theoretically fascinating behaviors, such as quantum spin liquids and symmetry-protected topological orders. In their theoretical analysis, entanglement entropy(EE) and spectrum(ES) often play an essential role as a quantitative indicator of the quantum many-body entanglement. Meanwhile, verifying quantum many-body entanglement in realistic quantum spin systems is still a challenging problem because EE and ES are not directly observable quantities. In this work, we discuss the angular-time evolution approach for spin operators to detect the ES in the ground state of the S=1 Heisenberg spin chain, which is well-known as a Haldane state. Such a protocol for the ES utilizing the angular-time correlation function was initially introduced for the XXZ chain based on the theoretical analogy between the Unruh effect in quantum gravity and the quantum entanglement structure for its bipartitioned ground state[1]. Moreover, recently, we successfully applied the protocol to the Affleck-Kennedy-Lieb-Tasaki (AKLT) chain, which has symmetry-protected topological entanglement associated with Z2 x Z2 symmetry, and found that the angular-time evolution can be interpreted as a real-time evolution of the edge state induced by a uniform magnetic field in the system part with the use of a gauge transformation for the matrix product state[2]. However, the AKLT chain is a rather mathematical model with no experimental counterpart. Using the density matrix renormalization group, we thus analyze the angular-time evolution for the ground state of the S=1 Heisenberg chain and then discuss whether we can correctly capture the ES in a realistic experimental situation. [1] K. Okunishi and K. Seki, J.Phys. Soc. Jpn. 88, 114002 (2019) [2] K. Nakajima and K. Okunishi, Phys. Rev. B 106, 134304 (2022)

#### Kohtaro Kato (Nagoya University):

**Exact renormalization flow for matrix product density operators**

Matrix Product Density Operators (MPDO) is a class of one-dimensional (1D) tensor network typically used to describe thermal states and fixed points of dissipative dynamics. MPDO is a generalization of Matrix Product States (MPS), which can describe 1D pure states efficiently. MPS is known to be connected to 1D gapped ground states, and its classification is done by studying the fixed points of exact (spatial) renormalization flow. In this submission, we study exact renormalization flow for MPDO to characterize the descriptive capability. We find that unlike MPS, MPDO does not admit exact renormalization flows in general. We then analyze MPDO with a well-defined renormalization flow and show that these MPDO can be characterized by generalized non-invertible symmetries.

#### Taishi Kawamoto (Yukawa Institute of Theoretical Physics):

**To wards proof of ETH in AdS/CFT**

The eigenstate thermalization hypothesis (ETH) provides a sufficient condition for thermalization and equilibration from any initial states in isolated systems with a large number of degrees of freedom. One part of this statement is that for large systems, the diagonal matrix elements of typical observables in the Hamiltonian eigenstate basis, that is, the expectation values of the energy eigenstates, depend smoothly on the corresponding energy values. This statement is highly related to the fact that the variance of the energy eigenstate expectation values is small. Indeed, it is conjectured that this variance shows power-law decay with respect to the Hilbert space dimension. On the other hand, in general relativity, it is expected that heavy objects undergo gravitational collapse. Additionally, it is known that gravitational systems with black holes exhibit maximally chaotic properties. By using the holographic principle, or specifically the AdS/CFT correspondence, these facts imply that holographic theories dual to higher-dimensional Einstein gravity will show chaotic behavior and also thermalization from high-energy states. Thus, we expect that holographic theories exhibit ETH, although there is no definitive proof for this. In this talk, we discuss that the variance of the eigenstate expectation values of primary and descendant operators shows power-law decay with respect to the Hilbert space dimension. This fact is derived from the quantum mixing properties of holographic theories with black hole gravitational duals. We also discuss the consequences of this scaling on thermalization. Moreover we show that the holographic theory with generalized free fields theory on AdS black hole give the double exponential small number of the quantum scar states in large N limit. This talk is based on work in progress.

#### Christy Kelly (RIKEN, iTHEMS):

**Ollivier Curvature Bounds in the Brownian Continuum Random Tree**

Scaling limits of discrete models of (Euclidean) quantum gravity often exhibit a pathological branched polymer phase; for instance the branched polymer is often interpreted as a manifestation of the tachyonic instability arising in Liouville theory beyond the $c=1$ barrier, while Euclidean dynamical triangulations appears to interpolate between a branched polymer phase and a crumpled phase with infinite Hausdorff dimension in spacetime dimensions $D>2$. Whilst the Regge calculus has traditionally been employed to interpret the regularised Euclidean Einstein-Hilbert action in the context of triangulations, recent mathematical developments in optimal transport theory have lead to new synthetic notions of (Ricci) curvature valid in a variety of coarse spaces. Indeed computations using one of these new synthetic curvatures due to Yann Ollivier indicate that the branched polymer is infinitely hyperbolic and thus likely to be suppressed in the Euclidean path integral if an alternative regularisation of the Einstein-Hilbert action is adopted.

#### Keun-Young Kim (Gwangju Institute of Science and Technology):

**Comments on quantum chaos and complexity**

Quantum chaos is one of the essential concepts in the fundamentals of quantum physics and black holes, as well as in applications such as quantum control, information processing, and quantum computing. Quantum (computational) complexity, along with entanglement, is also a very important concept in developing quantum algorithms and understanding the interior of black holes and the nature of spacetime. Recently, there has been active research on quantum chaos and complexity in quantum many-body systems, black holes, and their relationship based on the holographic principle. In this talk, we plan to overview the key concepts of these new developments, focusing on Krylov (spread, spectral) complexity and spectral form factors, and introduce important results. We will explain them using simple but significant physical systems such as quantum billiards and quantum spin chains. We will also discuss their relation to black hole physics and the Sachdev-Ye-Kitaev (SYK) model.

#### Keisuke Kitayama (RIKEN):

**Nonlinear optical responses in α-type organic salt**

Nonlinear optical responses, such as shift current, have been extensively explored from the perspectives of both fundamental science and electronic applications. However, nonperturbative effects in multiband systems are not well understood. In this talk, we investigate the DC photocurrent induced by linearly polarized light in α-(BEDT-TTF)2I3 [1]. There are two topics: (1) Second-order responses: Using perturbation theory, we discover that the direction of DC photocurrent strongly depends on the frequency of light, and this unique dependence is attributed to multiband effects. (2) Nonperturbative effects: Using Floquet theory, we find a change in the sign of DC photocurrent. We discuss the limitations of both the equation derived by the perturbation theory and the one derived by Morimoto and Nagaosa [2] when the light intensity is large. [1] K. Kitayama and M. Ogata, arXiv:2311.07176 (2023). [2] T. Morimoto and N. Nagaosa, Science Advances 2, e1501524 (2016).

#### Kotaro Kondo (National Institutes for Quantum Science and Technology):

**Short focused laser wakefield electron acceleration for experimental verification of the Unruh effect**

Quantum field theory predicts the Unruh effect, which states that a uniformly accelerated observer will see thermal radiation with a temperature proportional to the acceleration. The Unruh effect is related to the Hawking radiation by the equivalence principle, which can bridge interfaces among quantum information, quantum gravity, and statistical mechanics. Laser wakefield acceleration (LWFA) is an attractive method to generate a high acceleration field with the typical acceleration gradient of 100 GV/m, which is three orders of magnitude higher than that of a conventional radio frequency (RF) electron accelerator. However, the radiation temperature by this field gradient is still less than the liquid nitrogen temperature, which indicates that the experimental verification in this condition is difficult. While a long focus optic with LWFA is practically applied for high energy gain, a high intensity of laser and high electron density are essential for a localized high acceleration gradient. Here, we propose a short focused LWFA for high acceleration field to verify the Unruh effect. Particle in cell simulations show a high acceleration field beyond TV/m with realistic PW class laser parameters.

#### Hiroki Kuji (Tokyo University of Science):

**Proposal for realizing quantum-spin systems on a two-dimensional square lattice with Dzyaloshinskii-Moriya interaction by the Fl**

Floquet engineering is one of the powerful tools for engineering Hamiltonians in quantum simulators. In the previous works about the Rydberg atom quantum simulator, the method for constructing the XYZ Hamiltonian [1] and the Hamiltonian with the XY interactions and mono-axial Dzyaloshinskii-Moriya (DM) interactions [2] have been proposed. In this poster, we will present a method for constructing Hamiltonians with Heisenberg interactions and bond-dependent DM interactions using Floquet engineering in a system with an optical tweezers array of Rydberg atoms on a two-dimensional square lattice. [1]S. Geier et al., Science 374, 1149 (2021). [2]N. Nishad, et al., Phys. Rev. A 108, 053318 (2023).

#### Julian Lang (OIST):

**The supersymmetric U(N) vector model and higher-spin algebra; Why twistor-space is bigger than you thought**

In this talk we will study free spin-0 and spin-1/2 U(N) vector models in 3d in the context of the holographically dual type-A and type-B higher-spin (HS) gravity in 4d. There exists a twistor-space description relating single-trace boundary operators of spin-0 fields on the boundary, and linearized bulk fields in type-A HS gravity, to spacetime independent twistor functions, whose HS-algebra products reproduce all boundary correlators. I will show in this talk, that the space of spacetime independent twistor functions is larger than this: it includes twistor functions dual to all single-trace operators in the full N=1 supersymmetric extension of the boundary theory, including the supersymmetry generators themselves. We will discuss the implications of this for the bulk theory and give an infinite family of new ½-BPS “black hole” solutions.

#### Simon Lin (NYU Abu Dhabi):

**TT bar and the black hole interior**

In this talk/poster, I will argue that it is possible to access the interior of a holographic black hole using a boundary protocol based on TTbar deformation on the boundary CFT. This will be based on a work in progress with A. Almheiri and S. Ali-Ahmad.

#### Reita Maeno (Department of Physics, School of Science, University of Tokyo):

**Exploring efficient basis for quantum simulation of (2+1)-dimensional U(1) lattice gauge theory with finite density and temperat**

Bosonic Hilbert space needs to be truncated to carry out quantum simulation of (2+1)-dimensional U(1) model lattice gauge theory since it has infinite degrees of freedom. Since the effects of this truncation depend on bases, it is important to search efficient basis to obtain desired accuracy and low computational cost. This work focuses on searching efficient basis in (2+1)-dimensional U(1) model with finite density and temperature. Specifically, we compute thermal density matrices in different bases by diagonalizing the truncated Hamiltonian in each basis. By calculating the accuracy and the speed of convergence of observables varying truncation parameters with those bases under some configurations such as chemical potential, temperature, and couplings, we search the efficient basis and evaluate the number of qubits to achieve desired accuracy.

#### Kosuke Makino (Kindai University):

**Probing energy conditions around hairy black holes by gravitational waves**

Recently, hairy black holes have attracted much attention, as they can be regarded as an effective model of a black hole surrounded with dark matter and/or a quantum black hole. It is known that certain energy conditions are violated in some hair black hole solutions. It is of great interest to consider how to probe such hairy black holes, if exist in our universe, and the violation of the energy conditions via gravitational waves. In this talk, I will first review some examples of hairy black holes, e.g., Bardeen black holes and Hayward black holes, and show which type of energy conditions are violated in those hairy black hole solutions. Then, I will discuss how to probe the violation of energy conditions via quasi-normal modes (QNMs) by using WKB approximation.

#### Weibo Mao (Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences.):

**Local operator quench induced by two-dimensional inhomogeneous and homogeneous CFT Hamiltonians**

We explore non-equilibrium processes in two-dimensional conformal field theories (2d CFTs) due to the growth of operators induced by inhomogeneous and homogeneous Hamiltonians by investigating the time dependence of the partition function, energy density, and entanglement entropy. The non-equilibrium processes considered in this paper are constructed out of the Lorentzian and Euclidean time evolution governed by different Hamiltonians. We explore the effect of the time ordering on entanglement dynamics so that we find that in a free boson CFT and RCFTs, this time ordering does not affect the entanglement entropy, while in the holographic CFTs, it does. Our main finding is that in the holographic CFTs, the non-unitary time evolution induced by the inhomogeneous Hamiltonian can retain the initial state information longer than in the unitary time evolution.

#### Giacomo Marmorini (Nihon University):

**Measurement of entanglement in a many-body quantum simulator via spiral quantum state tomography**

Spiral quantum state tomography is an efficient protocol of reconstruction of the density matrix, particularly suitable for cold-atom quantum simulators since it does not require single-atom addressing. Here we theoretically demonstrate the possibility to measure certain entanglement properties of interesting many-body quantum states, such as entanglement and Renyi entropy, with adequate accuracy, after taking into account the main sources of noise.

#### Satoshi Matsumoto (Kindai University):

**No-hair properties of static black holes with cosmological constant in higher dimension**

We study no-hair properties of static black holes in four and higher dimensional spacetimes with a cosmological constant, and establish several theorems, which correspond to generalizations of Pena-Sudarsky's no-hair theorem, Nunez-Quevedo-Sudarsky's no-short-hair theorem and Sudarsky-Gonzalez's no-hair theorem to heigher dimension. For the vanishing cosmological constant case, we show a no-hair theorem and also a no-short-hair theorem under certain conditions for the energy-momentum of matter fields. For the positive cosmological constant case, we discuss conditions for hairy static black holes to exist in terms of the energy density of matter fields evaluated at the black hole horizon and the cosmological horizon. For the negative cosmological constant case, we study conditions for hairy black holes by presenting a no-hair theorem in which the asymptotic structure is assumed to be determined by the true cosmological constant. This talk is based on the paper of A. Ishibashi, S. Matsumoto, Y. Yoneo, arXiv number 2310.16395 [gr-qc].

#### Akira Matsumoto (Yukawa Institute for Theoretical Physics, Kyoto University):

**Computing theta-dependent mass spectrum of the 2-flavor Schwinger model by tensor network**

We compute the theta-dependent mass spectrum of the 2-flavor Schwingr model using the density-matrix renormalization group. The composite particles of the model, the pion and the sigma meson, are identified as stable particles while the eta meson becomes unstable at nonzero theta. The meson masses are obtained from the one-point functions, using the meson operators defined by diagonalizing the correlation matrix to deal with the operator mixing. We also compute the dispersion relation directly by measuring the energy and momentum of the excited states, where the mesons are distinguished by the isospin quantum number. The meson masses computed by these methods agree with each other, and they are consistent with the calculation by the bosonized model as well. Furthermore, the one-point functions reproduce the expected CFT-like behavior at the critical point theta=pi, where the mesons become almost massless. These methods can be complementary approaches to the conventional Monte Carlo simulation when the sign problem is an obstacle.

#### Yoshinori Matsuo (Kindai University):

**Universal structure of islands in evaporating black holes**

We discuss universal behaviors of islands in black hole spacetimes. The entanglement entropy of Hawking radiation contains contributions from a region inside the horizon, which is called the island. Islands extend outside the horizon in the case of eternal black hole spacetimes, while are terminated behind the horizon in the case of evaporating black holes. This structure does not depend on details of the spacetime. We use the s-wave approximation for the matter part of the entanglement entropy, and see effects of islands explicitly. The gravity part pulls the quantum extremal surface outward while the matter part pushes it inward. We found that the effect of the matter part is stronger independent of details of the spacetime, and the island in evaporating black holes is always hidden behind the horizon.

#### Arpita Mitra (POSTECH, South Korea):

**Krylov complexity of deformed conformal field theories**

We consider a perturbative expansion of the Lanczos coefficients and the Krylov complexity for two-dimensional conformal field theories under integrable deformations. Under $T\bar{T}$ deformation, we demonstrate that the Lanczos coefficients exhibit unexpected behavior, deviating from linear growth within the valid perturbative regime. Notably, the Krylov exponent characterizing the rate of exponential growth of complexity surpasses that of the undeformed theory for positive value of deformation parameter, suggesting a potential violation of the conjectured operator growth bound within the realm of perturbative analysis. One may attribute this to the existence of logarithmic branch points along with higher order poles in the autocorrelation function compared to the undeformed case. In contrast to this, both $J\bar{J}$ and $J\bar{T}$ deformations induce no first order correction to either the linear growth of Lanczos coefficients at large-n or the Krylov exponent and hence the results for these two deformations align with those of the undeformed theory.

#### Akihiro Miyata (Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences):

**Hawking-Page and entanglement phase transition in 2d CFT on curved backgrounds**

The thermodynamics and the entanglement properties of two-dimensional conformal field theories (2d CFTs) on curved backgrounds are studied. By means of conformal mapping we study the equivalent system on flat space governed by the deformed Hamiltonian, which is a spatial integral of the Hamiltonian density modulated by an enveloping function. Focusing on holographic CFTs, we observe Hawking-Page like phase transition for the thermal and the entanglement entropy as we vary the background metric. We also compute the mutual information to study the information theoretic correlation between parts of the curved spacetime. The gravity dual of 2d CFTs on curved background is also discussed.

#### Yuki Miyazaki (Aoyama Gakuin University):

**Permutationally invariant part of a density matrix: Rényi entropy across quantum phase transitions**

It is becoming clear that the concepts originating from quantum information theory are useful for the analysis of quantum many-body physics. For example, it is known that the so-called topological entanglement entropy, which is a universal constant in the von Neumann entanglement entropy, characterizes topologically ordered phases [1, 2]. In modern condensed matter physics, there is a growing demand for both theoretical analysis and experimental measurement of quantities related to quantum information. Given the density matrix of a system, we can, in principle, obtain quantum information about the system, including its entanglement entropy, when the system is divided into two parts. However, in the field of solid state physics, experimentally obtaining the density matrix of a system is challenging because we can basically measure only macroscopic observables such as magnetization, electrical resistance, and so on. In artificial quantum systems including cold atomic gases in an optical lattice [3], trapped-ion systems [4], etc., the simulation of quantum many-body physics can be conducted in an ideal environment. Taking advantage of the cleanness and high controllability of such systems, the reconstruction of a density matrix of multi-qubit systems has been successfully achieved by preparing the identical state repeatedly and measuring the various microscopic observables. This process is known as quantum state tomography (QST). However, the QST for a density matrix of entire systems has been limited to small systems (at most 8 qubits so far [5]) due to the exponentially increasing cost with respect to the system size. In this work, we investigate the role of the permutationally invariant part of the density matrix (PIDM) in capturing the properties of the ground state of the system across a quantum phase transition [6]. PIDM is defined as the average over all possible site permutations of the density matrix. In the context of QST, it is recognized that PIDM requires only a polynomial number of measurements, in contrast to the exponential cost associated with reconstructing a full density matrix. Here, we examine the possible application of this experimentally tractable quantity to the analysis of phase transition phenomena. Specifically, considering the transverse-field Ising and XXZ chains as examples, we compute the second-order Rényi entropy of PIDM for the ground state by using the density matrix renormalization group algorithm. As a result, we find different size-scaling behaviors of the Rényi entropy of PIDM depending on the phase. We discuss the underlying causes of those behaviors by employing the second-order perturbation theory. [1] A. Kitaev and J. Preskill, Physical Review Letters 96, 110404 (2006). [2] M. Levin and X.-G. Wen, Physical Review Letters 96, 110405 (2006). [3] I. Bloch, Nature Physics 1, 23 (2005). [4] R. Blatt and C. F. Roos, Nature Physics 8, 277 (2012). [5] H. Häffner et al., Nature 438, 643 (2005). [6] Y. Miyazaki, G. Marmorini, N. Furukawa, and D. Yamamoto, arXiv:2404.08389.

#### Sukrut Dattaprasad Mondkar (Harisch-Chandra Research Institute):

**Learning Holographic Horizons**

We apply machine learning to understand fundamental aspects of holo- graphic duality, specifically the entropies obtained from the apparent and event horizon areas [1]. We show that simple features of only the time series of the pressure anisotropy can predict the areas of the apparent and event horizons in the dual bulk geometry at all times. Given that simple Vaidya-type metrics constructed just from the apparent and event horizon areas can be used to approximately obtain unequal time correlation functions [2], we argue that the corresponding entropy functions are the measures of information that need to be extracted from simple one-point functions to reconstruct specific aspects of correlation functions of the dual state with the best possible approximations. 1. V. Jejjala, S. Mondkar, A. Mukhopadhyay and R. Raj, arXiv:2312.08442v2 2. L. K. Joshi, A. Mukhopadhyay, F. Preis, P. Ramadevi, Phys. Rev. D 96 (10) (2017) 106006. arXiv:1704.02936

#### Javier Moreno (Universidad de Concepción):

**Higher-dimensional Willmore energy as holographic entanglement entropy**

We show that the finite universal part of the holographic entanglement entropy for Einstein-AdS gravity in 6D is equal to generalized Willmore energy in 4D, when considering the ground state of the CFT which is dual to the Poincaré patch of pure AdS. The generalized Willmore functional is evaluated on a doubled version of the same Ryu-Takayanagi surface considered in the entropy computation, but embedded in $\mathcal{R}^5$. The Willmore energy is shown to come from a conformal-invariant codimension-2 functional obtained by evaluating Conformal Gravity in 6D on the conically-singular orbifold of the replica trick. The finite universal part of the entanglement entropy is shown to come from the same conformal invariant, making the equality manifest. This equality is tested on several geometries including the half cylinder and the hemisphere Ryu-Takayanagi surfaces and some deformations thereof

#### Takato Mori (Perimeter Institute/Yukawa Institute for Theoretical Physics):

**Locally accessible information/quantum discord in holography and many-body systems**

We investigate the gravity dual of the locally accessible information (LAI). In contrast to entanglement quantities, the LAI is sensitive to the optimality of the subsystem measurements as well as the correlation of a quantum state. Moreover, it is related to quantum discord, which includes a quantum correlation beyond entanglement. We find that the semiclassical calculation corresponds to a simple measurement by comparing to a random unitary toy model. We also show that the result conflicts with quantum information theory and hence a large enhancement of quantum or nonperturbative corrections is expected. Inspired from the information recovery protocols for black holes, an explicit protocol for the enhancement is presented in the random unitary model and a possible gravitational interpretation is discussed. Finally, we study the properties of these gravity duals in many-body systems by translating them to the boundary quantities. This approach offers new efficiently-computable alternatives to the LAI and new connections to measurements, entropy, and complexity.

#### Debangshu Mukherjee (Asia Pacific Center for Theoretical Physics):

**Emergent factorization of Hilbert space at large N and black hole**

I plan to discuss the emergent factorization of Hilbert space in the low-energy description of a simple matrix model, addressing key aspects of the black hole information paradox. this toy model will lead to a concrete mechanism for constructing the truncated algebra of accessible observables, thus providing a better understanding of black hole complementarity. I will also comment on the island conjecture and holography of information.

#### Abhishek Navhal (Tata Institute of Fundamental Research (TIFR), Mumbai):

**Classification of Monodromies in Lorentzian 2D CFT Correlators**

In Euclidean space four point CFT correlators, f(z,\bar {z} = z*) (normalized by products of two point functions) are single valued functions of two cross ratios (z and \bar{z} = z*). As a mathematical exercise, consider the analytic continuation of Euclidean correlators where z and \bar{z} are independent complex variables. Then correlators are no longer single-valued, but have a rich branch structure, with (generically) exponential growth in the number of independent sheets as a function of monodromy number. It is natural to ask whether the value of f(z,\bar{z}) on every sheet is the answer to a physical question of interest such as ‘something happening’ in the bulk? It is well known that some sheets (e.g. the well studied Regge configurations) have a simple physical interpretation of going to Lorentzian space. In this poster, we enumerate all sheets that can be reached in this manner by studying time ordered correlators on the Lorentzian cylinder. It turns out this gives us access to an infinite sequence of branching sheets. Though our answer is an infinitesimal fraction of the full (generically exponentially growing) set of sheets of f(z,\bar{z}) . Turning the question around, we find a clear definitive answer to the question “On which sheet does a Lorentzian time-ordered correlator lie for arbitrary locations of the four insertion points in AdS boundary in 2D?”.

#### Ryo Nemoto (Nagoya University):

**Algebraic ER=EPR in LLM**

In recent years, in the field of quantum gravity, the theory of operator algebras which treats quantum entanglement strictly is becoming a useful tool for analyzing quantum systems. Discussions based on this method reveal some nontrivial features of concrete physical systems such as the de Sitter space or Black holes. Following this trend, the "Algebraic ER=EPR conjecture" was proposed last year, which might provide a unified understanding of the relation between quantum entanglement and quantum gravity by using the theory of operator algebras. In this poster, we will verify the claim of this conjecture using Lin-Lunin-Maldacena (LLM) geometry, a system whose correspondence between gravity theory and field theory is perfectly known, and aim to clarify the relationship between quantum entanglement and spacetime.

#### Soshun Ozaki (Basic Science, UTokyo):

**Disorder-free Sachdev-Ye-Kitaev models: Integrability and a precursor of chaos**

We introduce two disorder-free variants of the Sachdev-Ye-Kitaev (SYK) model, demonstrate their integrability, and study their static and dynamical properties. We find that out-of-time-order correlators (OTOCs) in these models exhibit exponential-like growth at early times while random-matrix behaviors in level statistics and the spectral form factor are absent. Our findings illustrate that the SYK variants represent simple but nontrivial examples of disorder-free quantum many-body systems displaying chaos-like behavior of OTOCs. We also discuss the dynamics of the SYK variants in the presence of dissipation.

#### Himanshu Parihar (National Center for Theoretical Sciences, National Tsing Hua University, Taiwan):

**Holography for Boundary Lifshitz Field Theory**

We propose a holographic duality for the boundary Lifshitz field theory (BLFT). Similar to holographic BCFT, holographic BLFT can be consistently defined by imposing either a Neumann boundary condition (NBC) or a conformal boundary condition (CBC) on the end of the world (EOW) brane. We propose g-functions and derive g-theorem for these two types of holographic BLFT. On the field theory side, we consider BLFT whose path integral is prescribed to include also paths bouncing off the boundary. The entanglement entropy for an interval for the Lifshitz invariant ground state is computed in the saddle point approximation, and is found to agree precisely with the holographic result in both limits when the interval is very close or very far away from the boundary.

#### Pranay Patil (Okinawa Institute of Science And Technology):

**Tunable scale of topological protection in a triangular lattice of Rydberg atoms**

Rydberg atom arrays have recently been conjectured to host $Z_2$ quantum spin liquids in certain parameter regimes. Due to the strong interactions between these atoms, it is not possible to analytically study these systems, and one must resort to Monte Carlo sampling of the path integral to reach definite conclusions. The complex landscape of path integral configurations prevents efficient sampling, and leads to a severe lack in ergodicity for the Monte Carlo simulation. Here we use the resonances expected between different configurations of a $Z_2$ spin liquid to design a sampling protocol which is especially suited to the expected path integral landscape. This allows us to reliably simulate Rydberg atoms on a triangular lattice in this regime, and identify a correlated paramagnetic phase at low temperatures which hosts topological protection similar to a $Z_2$ spin liquid upto a lengthscale tuned by Hamiltonian parameters.

#### Aaron Poole (National Taiwan University):

**Charges, conserved quantities, and fluxes in de Sitter spacetime**

This talk is motivated by the broad aim of a developing a fully nonlinear understanding of the nature of gravitational waves in asymptotically (locally) dS spacetimes. I will begin with a review of the asymptotics of dS spacetimes, before showing (via the covariant phase space formalism) that spacetimes admitting suitable symmetries have spatially conserved charges. Relaxing the global requirement of such symmetries, I will present flux formulae which capture the effects of outgoing gravitational radiation and illustrate these via application to exact solutions, with particular emphasis on the Robinson-Trautman dS class. This talk is based on Phys.Rev.D 106 (2022) 6, L061901 and upcoming work in collaboration with Kostas Skenderis and Marika Taylor.

#### Sneha Pradhan (BITS Pilani Hyderabad Campus):

**A Comprehensive Study of Massive Compact Star Admitting Conformal Motion Under Bardeen Geometry.**

This article primarily investigates the existence of the charged compact star under the conformal motion treatment within the context of f(Q) gravity. We have developed two models by implementing the power-law and linear form of conformal factor, enabling an in-depth comparison in our study. We have selected the MIT Bag model equation of state to describe the connection between pressure and energy density and matched the interior spherically symmetric space-time with the Bardeen space-time. In addition, the present research examines various physically valid characteristics of realistic stars, such as PSR J1614-2230, PSR J1903+327, Vela X-1, Cen X-3, and SMC X-1. We compare two constructed models by attributing the behavior of density, pressure, equilibrium conditions, and the adiabatic index. We have additionally included a brief analysis of the scenario involving Reissner-Nordstrom spacetime as an external geometry for the matching condition. In contrast to the Reissner-Nordstrom instance, the Bardeen model with the extra term in the asymptotic representations yields a more intriguing and viable result. The current analysis reveals that the resulting compact star solutions are physically acceptable and authentic when considering the presence of charge with conformal motion in f(Q) gravity.

#### Geet Rakala (OIST):

**Efficient Real Space SDRG for Disordered Ising Models at Finite Temperatures.**

We have developed a numerical algorithm for the efficient execution of real space strong disorder renormalization group (SDRG) in disordered systems with discrete variables. This algorithm is applied to investigate the entanglement properties of random transverse field Ising models at finite temperatures. The method achieves computational efficiency by leveraging the inherent commutativity of all RG steps, coupled with Dijkstra's algorithm for rapid identification of the next decimation step. Finite temperature behavior is examined by imposing a lower bound on the energy scales for decimation, set by the temperature itself. The potential for extending this methodology to systems with continuous variables will also be discussed.

#### Salvatore Ribisi (CPT - Marseille):

**Light-cone thermodynamics**

After a brief introduction of the previous works on Light-cone thermodynamics done by Perez and De Lorenzo, I will present the results of our last paper. Here, we explicitly express the Minkowski vacuum of a massless scalar field in terms of the particle notion associated with suitable spherical conformal killing fields. These fields are orthogonal to the light wavefronts originating from a sphere with a radius of rH in flat spacetime: a bifurcate conformal killing horizon that exhibits semiclassical features similar to those of black hole horizons and Cauchy horizons of spherically symmetric black holes. Our result highlights the quantum aspects of this analogy and extends the well-known decomposition of the Minkowski vacuum in terms of Rindler modes, which are associated with the boost Killing field normal to a pair of null planes in Minkowski spacetime (the basis of the Unruh effect). At last, I will briefly discuss the connection between this work and ongoing research in the fields of conformal quantum mechanics, the thermodynamic properties of causal diamonds in general spacetimes as well as recent works in emergent gravity.

#### Mayank Roy (requested to not publish in list of attendees):

**Transmission Resonance in Quantum Waveguides and Effect of Ultracold Materials**

Waveguides are commonly used structures for transmitting electromagnetic waves (and energy) through a medium, restricting transmission in a certain direction and mode of propagation. A previous work of mine studied propagation of EM waves through waveguides under TE and TM propagation modes under a regular temperature reduced graphene oxide medium and I also analyzed the mathematical boundary condition through weighted residual method for energy minimalization. In my current research, I am analyzing Quantum Waveguides in a rigorous mathematical approach. At this moment, my study pertains to perturbation with respect to Dirichlet Laplacians in R^3 and its quantum waveguide spectra. The main aim is to analyze flux distribution in the waveguide as a function of potential and understand the scattering problem and study the system in a ultracold simulation of various matter for analysis. The current simulation once again uses reduced graphene oxide to study the quantum scattering phenomena but with ultracold atoms. I may also extend the scope to other materials and study the developed system for quantum communications.

#### Snigdh Sabharwal (OIST):

**Witnessing Disorder in Spin Chains**

There are no clean samples in nature. Therefore, can one meaningfully quantify the effects of disorder on the entanglement structure of quantum states. In this work, we investigate the entanglement structure of Tomonaga-Luttinger liquids (TLL) and random singlet (RS) states using entanglement witnesses. Using quantum Fisher information (QFI) we demonstrate that both TLL and RS states exhibit multipartite entanglement. We attribute the observed multipartiteness in the RS state to the localization of multipartite clusters below the crossover lengths. Additionally, we explore how the order of disorder averaging affects the pairwise entanglement distribution as measured by concurrence. Finally, we show that the low-temperature behavior of these witnesses can characterize the effects of disorder. From the low-temperature behavior of concurrence, we extract the central charge information for the TLL state and conjecture this could be done for the RS state as well. Furthermore, using the equal-time structure factor as a multipartite entanglement witness, we demonstrate a distinct growth in multipartite entanglement in both states.

#### Sunil Kumar Sake (YITP):

**York slicing in JT gravity**

We construct states in JT gravity with extrinsic curvature of the slice playing the role of clock. In the path integral language, these states correspond to evaluating the path integral with an asymptotic boundary where dilaton and metric are held fixed and another boundary where the metric and extrinsic curvature of the curve are held fixed. We explicitly check that these states satisfy the WDW equation and thus are phyiscal states of the theory. We also show that the states we construct can be understood as the eigenstates of the Hamiltonian of the Lorentzian theory. We end with an interpretation of these states in the dual matrix model.

#### Yunseok Seo (Kookmin University, Seoul, Korea):

**Construction of Superconducting Dome and Emergence of Quantum Critical Region in Holography**

In this work, we investigate an extended model of holographic superconductor by a non- linear electrodynamic interaction coupled to a complex scalar field. This non-linear inter- action term can make a quantum phase transition at zero temperature with finite charge carrier density. By solving full equations of motion, we can construct various shapes of the superconducting phase in the phase diagram. With a specific choice of interaction coeffi- cients, we can construct a phase diagram with a superconducting dome. Also, we find a new geometric solution inside the superconducting dome, which turns out to be a Lifshitz-type geometry. This geometry is characterized by a dynamical critical exponent, which plays a crucial role near the quantum critical point. We refer to this region in the phase diagram as a ‘quantum critical region.’

#### Yuta Shingu (Tokyo University of Science):

**Controlled-time-evolution free imaginary time evolution**

Computing expectation values with the Gibbs state is a key application in many fields. Imaginary time evolution is a promising way to estimate the expectation values by preparing the thermofield double state. Error resilient Monte Carlo method is an accurate method to compute imaginary time evolution with quantum computation. However, this algorithm requires controlled real-time evolution, leading to a significantly deep circuit. Here, we propose a method to make the circuit quite shallower. We assume that we know an eigenstate (which does not have to be the ground state) of the Hamiltonian beforehand. By starting from the superposition of the eigenstate and the maximally entangled state, we can replace the controlled real-time evolution with just the real-time evolution.

#### Kotaro Shinmyo (Yukawa Institute for Theoretical Physics):

**Probing de Sitter Space Using CFT States**

We construct CFT states dual to local excitations in the three-dimensional de Sitter space (dS), called the bulk local states. We find that the conjugation operation in dS3/CFT2 is notably different from that in AdS3/CFT2. This requires us to combine two bulk local states constructed out of different primary states in a CPT-invariant way. This analysis explains why Green's functions in the dS Euclidean vacuum cannot simply be obtained from the Wick rotation of those in AdS. We also argue that this characteristic feature explains the emergence of time coordinate from the dual Euclidean CFT. We show that the information metric for the quantum estimation of bulk coordinate values replicates the de Sitter space metric.

#### Oded Shor (Tel Aviv university):

**Relational information framework: causality, unification of quantum interpretations and return to realism through non-ergodicity**

In the framework of relational information, we explore analogs of physical theories and their properties. Specifically, we investigate the causal characteristics of relational information, examining how initial knowledge impacts future relational understanding of the universe/system. To achieve this, we establish a parameter space defining relational structures called dendrograms, exhibiting causal properties akin to those of Minkowski metric. Subsequently, we propose a statistical-dynamical model on this Minkowski-like parameter space, unifying Bohmian and Many Worlds interpretations of quantum theory in the framework of relational information. Additionally, we provide an analytical proof of the non-ergodicity of the relational information framework, revealing CHSH inequality violations as an emergent phenomenon. Our focus on relational information underscores its significance across scientific disciplines, where a single measurement or observation lacks meaning without context.

#### Yu-ki Suzuki (Yukawa Institute for Theoretical Physics):

**TBA**

TBA

#### Hiromasa Tajima (Nagoya University):

**Stochastic inflation and entropy bound in de Sitter spacetime**

We analyze the entropy behavior of the de Sitter spacetime during the inflationary phase. In the de Sitter spacetime, a cosmological horizon that constrains the causal accessible region of an observer, exhibits thermal properties analogous to the event horizon of a black hole. From the principle of holography, the entropy within the causally connected region for an observer is constrained by the area of its boundary. This entropy bound is violated in the late stage of inflation. To address the issue of entropy bound violation from a perspective of quantum information, we adopt the stochastic approach to cosmic inflation. To reformulate the issue of entropy bound in the inflation, we follow the derivation of the Page curve in the black hole context. By adopting the volume-weighted probability distribution for the inflaton field, we obtain a meaningful entropy behavior in the de Sitter spacetime.

#### Yusuke Taki (YITP):

**The semi-classical saddles in three-dimensional gravity via holography and mini-superspace approach**

We determine the complex geometries dual to the semi-classical saddles in three-dimensional gravity with positive or negative cosmological constant. We examine the semi-classical saddles in Liouville field theory and interpret them in terms of gravity theory. For this, we describe the gravity theory by Chern Simons theory and classify the possible saddles based on the winding number. We further realize the semi-classical saddles using the mini-superspace model of quantum gravity and explicitly determine the integral contour. In the case of positive cosmological constant, we recovered the geometry used for no-boundary proposal of Hartle and Hawking. In the case of negative cosmological constant, the geometry can be identified with Euclidean anti-de Sitter space attached with imaginary radius spheres. The geometry should be unphysical and several arguments on this issue are provided.

#### Akane Tanaka (Kindai University):

**Quantum focusing conjecture and black hole/string transition**

In general relativity, the focusing theorem is key to understanding the basic properties of gravitation. By combining the Raychaudhuri equation and certain energy conditions, the focusing theorem plays a central role in establishing various important results in general relativity, such as the singularity theorems[1]. But the focusing theorem is violated with quantum effects taken into account. The quantum focusing conjecture(QFC) was devised to solve this problem[2]. In the context of the black hole evaporation, the entanglement entropy of the Hawking radiation is decreasing after the Page time[3], and therefore it is not obvious whether the QFC holds in the black hole evaporation process especially after the Page time. The previous study[4] showed that the QFC is indeed satisfied in this context. However the background considered in [4] was approximated by the Vaidya metric, and quantum effects of matters in the semiclassical regime were not fully taken into consideration. In this presentation, I address this problem in a two-dimensional dynamical black hole of the Russo-Susskind-Thorlacius (RST) model[5], which allows us to solve the semiclassical equations of motion exactly. I will first give a suitable definition of the quantum expansion in two-dimensions and then prove that the QFC is satisfied for evaporating black holes in the RST model with the island formation taken into account[6]. As an extension of the results of [6], I will discuss a possible endpoint for the black hole evaporation. Specifically, I will explore the possibility of the black hole/string transition. [1]R. Penrose, Phys. Rev. Lett. 14 (1965) 57-59. [2] R. Bousso, Z. Fisher, S. Leichenauer, and A.C. Wall, Phys. Rev. D93 (2016) 064044. [3] D.N. Page, Phys. Rev. Lett. 71 (1993) 3743. [4] Y. Matsuo, JHEP12 (2023) 050. [5] J.G. Russo, L. Susskind, and L. Thorlacius, Phys. Rev. D46 (1992) R1005. [6] A. Ishibashi, Y. Matsuo, A. Tanaka, arXiv:2403.19136[hep-th].

#### Kenya Tasuki (Yukawa Institute for Theoretical Physics, Kyoto University):

**Entropic g-theorem from strong subadditivity**

In the study of quantum field theory, constructing functions that represent effective degrees of freedom and demonstrating their monotonic decrease under the renormalization group (RG) flow is a significant problem. Recently, there has been increasing interest in constructing such monotonically decreasing functions from the quantum informational properties of quantum field theory. In this presentation, we demonstrate that a monotonically decreasing function (the g-function) can be constructed for boundary RG flows in two-dimensional conformal field theories, using the strong subadditivity of entanglement entropy.

#### Mritunjay Tyagi (University College Groningen, University of Groningen):

**Exploring the Husimi Q Function: Prospects, Challenges and connection with Deformation quantization**

If one could understand quantum states as encoding probability functions on phase space in analogy to probability distributions in classical statistical mechanics, this might be seen as providing an attractive solution to the measurement problem in quantum mechanics. Indeed phase space distribution functions are widely used in quantum mechanics as a powerful tool to calculate expectation values of operators corresponding to classical observables. However, the more commonly used phase space distribution function, Wigner function, is only interpreted as a quasi-probability function on phase space since it can take negative values. Another important phase space distribution function, the Husimi Q function, is positive semi-definite. Interpreting it as a proper probability distribution has recently been proposed by Drummond and Reid as well as Friederich. In this poster we discuss conceptual features of this interpretation and its empirical adequacy. We show that it is intricately related to a quantization scheme known as the Berezin (deformation) quantization (or, more popularly, anti-Wick quantization). We also emphasize the relationship between Berezin quantization and the more popular Weyl quantization on flat real phase space. For classical observables quantized through Berezin deformation quantization, Q functions are a natural choice of phase space distribution function, which indeed allows one to draw parallels to classical statistical mechanics. Moreover, considering the foundations of the quantization procedure also raises doubts on the assumptions of the Kochen-Specker theorem, and we try to address them coherently using the scheme of anti-Wick quantization.

#### Kenta Ueda (Department of Physics, Kindai University):

**Anomalous tunneling of collective excitations in a Rydberg atomic system described by a spin-1/2 XY model with dipole-dipole int**

We study tunneling properties of low-energy excitations through a potential barrier in a spin-1/2 ferromagnetic XY model with dipole-dipole interactions, which has been realized with Rydberg atoms in an optical tweezer array [1]. In a system with spontaneous breaking of U(1) symmetry and short-range interaction, it is known that low-energy excitations exhibit anomalous tunneling behavior, in which the transmission probability increases with decreasing the excitation energy and the barrier is completely transparent at the zero-energy limit [2]. We aim to elucidate how the long-range nature of the dipole-dipole interaction affects such tunneling properties of the low-energy excitations. Specifically, within a mean field theory, we numerically calculate the transmission probability as a function of the excitation energy in order to show that the anomalous tunneling indeed occurs in the present system. We also find that the width at half-maximum of the peak of the transmission probability is inversely proportional to the fourth root of the barrier strength, which is a unique behavior resulting from long-range interactions. [1] C. Chen et al., Nature, 616, 691 (2023). [2] Yu. Kagan et al., PRL 90, 130402 (2003).

#### Tatsuaki Wada (Ibaraki University):

**A Hamiltonian approach to the gradient-flow equations in information geometry**

Information geometry is a useful framework for studying some families of probability distributions. We have studied the gradient-flow equations in information geometry from different perspective, and related to the different fields in physics such as analytical mechanics, geometric optics, thermodynamics, general relativity, cosmology and so on. Based on the motion of a null (or light-like) particle in a curved space, we have derived the Hamiltonians which describe the gradient-flows in information geometry.

#### Gopal Yadav (Chennai Mathematical Institute):

**Probing the cosmological singularities with complexity and entanglement**

This talk is based on arXiv: 2404.00761. We studied holographic volume complexity for various families of holographic cosmologies with Kasner-like singularities, in particular with $AdS$, hyperscaling violating and Lifshitz asymptotics. We found through extensive numerical studies that the complexity surface always bends in the direction away from the singularity and transitions from spacelike near the boundary to lightlike in the interior. As the boundary anchoring time slice approaches the singularity, the transition to lightlike is more rapid, with the spacelike part shrinking. The complexity functional has vanishing contributions from the lightlike region so in the vicinity of the singularity, complexity is vanishingly small, indicating a dual Kasner state of vanishingly low complexity, suggesting an extreme thinning of the effective degrees of freedom dual to the near singularity region. We also developed further previous studies on extremal surfaces for holographic entanglement entropy, and found that in the IR limit they reveal similar behaviour as complexity.

#### Takaharu Yoshida (Tokyo University of Science):

**Proposal for experimental realization of quantum spin chains with quasiperiodic interaction using Rydberg atoms**

Ultracold atom experiment provides platforms to study nonequilibrium dynamics in isolated quantum systems such as many-body localization which occurs in disordered interacting systems. Systems with diagonal quasiperiodicity are considered to host conventional many-body localization. However, recent research reported that an anomalous localization phenomenon called many-body critical regime emerges in systems with off-diagonal quasiperiodic interaction. In our poster, we propose a quantum spin model where such a phenomenon was confirmed with a scheme for experimental realization using Rydberg atoms. We also show some results of our computational calculation.

#### Daisuke Yoshida (Nagoya University):

**First law and the weak cosmic censorship for de Sitter black holes**

We investigate the covariant phase space approach to de Sitter black hole. Evaluating the first order identity for the Noether charge associated with the static Killing vector of the background static black hole, we obtain the first law of the black hole thermodynamics with respect to the Abbott-Deser mass and the Wald entropy for black hole. We extend the discussion by Sorce-Wald about the gedanken experiment to destroy an asymptotically flat charged black hole to an asymptotically de Sitter one. Then, we find that the charged black hole in de Sitter space can not be overcharged by any energy sources if the null energy condition is satisfied.

#### Riku Yoshimoto (Nagoya university):

**Gravitational anomaly and Hawking radiation in quantum Hall system with an expanding edge**

The relationship between gravitational anomaly and Hawking radiation from black holes was revealed by Wilczek and Robinson. They considered the cancellation of gravitational anomaly arising from ignoring ingoing modes that do not affect external dynamics near the horizon of a black hole (BH), thereby demonstrating the occurrence of Hawking radiation. We apply this method to quantum Hall system with an expanding edge. This system has an edge excitation which corresponds to chiral scalar field in analog de Sitter spacetime. In such situation, it is known that gravitational anomaly exists. We can obtain boundary conditions between flat region and de Sitter region by considering the cancellation of gravitational anomaly for diffeomorphism invariance and it leads Hawking radiation.

#### Hirotaka Yoshino (Osaka Metropolitan University):

**Distorted static photon surfaces in electrovacuum spacetimes**

The photon surface is defined as a timelike surface S such that any photon emitted in arbitrary tangential direction to S from an arbitrary point on S continues to propagate on S. In this poster, I show that a static photon surface can be present in distorted electrovacuum spacetimes with perturbative approach, by constructing analytic solutions to the equations for static perturbations of a Reissner-Nordström spacetime that are regular outside the background photon surface. Our results imply that the uniqueness of the photon surface may not hold in electrovacuum spacetimes.

#### Atis Yosprakob (Niigata University):

**Toward tensor renormalization group study of quantum chromodynamics**

The tensor renormalization group (TRG) method is a powerful tool for studying lattice field theories and quantum many-body systems that is free from the sign problem. In this talk, I discuss two of the recent developments toward the TRG study of lattice QCD. The first is the proposal for incorporating multiple fermion flavors for 2D Abelian gauge theory, using the Grassmann tensor network. The second is the proposal for the reduced tensor network formulation for non-Abelian pure gauge theories in arbitrary dimensions. These two techniques are essential for the efficient computations of non-Abelian gauge theories with multiple flavors, including quantum chromodynamics.

#### Nicolò Zenoni (Yukawa Institute for Theoretical Physics, Kyoto University ):

**Multipartite information in sparse SYK**

The Sachdev-Ye-Kitaev (SYK) model, a quantum mechanical system involving N-flavoured Majorana fermions which interact with random couplings, has gained interest as a toy model for holography. Recently, a sparse version of the SYK model has been considered, in which some of the couplings are randomly set to zero. Up to some degree of sparseness, it has been argued that such a theory still admits a gravity dual. In the context of quantum field theories, multipartite information among disjoint spatial regions can detect the existence of a holographic dual. In this seminar, we discuss the SYK analog of multipartite information, which captures the entanglement among different flavours. In particular, we study how this notion of multipartite information behaves as a function of the sparseness and we comment on the possible outcomes regarding the presence of a gravity dual.