arXiv subjects

Daichi Takeda

Publications and source records attributed to Daichi Takeda.

15 recordsLinked to original sources

arXiv2026

A Lindbladian for holographic Brownian motion

We derive a Lindbladian description of holographic Brownian motion in the high-temperature regime. Starting from the influence functional for a trailing string endpoint, we identify the corresponding quantum master equation and prove that it is completely positive and trace-preserving. We determine the coefficients of the Lindbladian explicitly for two holographic backgrounds: the BTZ black hole and the AdS$_5$ black brane, restricting in the latter case to the endpoint fluctuation along the $x^1$-direction. We then analyze the time evolution of phase-space moments, energy relaxation, and steady states.

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arXiv2026

Holographic Schwinger-Keldysh effective action for heavy quarks in confinement and deconfinement phases

The holographic Schwinger-Keldysh (SK) prescription proposed by Skenderis and van Rees (SvR) has the advantage of being applicable whether or not the gravity dual contains a black hole. Taking advantage of this feature, we derive the quadratic effective action for a quark-antiquark pair in the confinement phase within the holographic SK framework of SvR. We also apply the SvR prescription to derive the quadratic effective action for a single heavy quark moving at a constant velocity in a nonequilibrium steady state in the deconfinement phase.

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arXiv2026

Black-hole formation and thermalization in open JT gravity

Black-hole formation is expected, via holography, to correspond to thermalization in the boundary theory. For open quantum systems, an initial pure state generically evolves into a mixed state irreversibly, suggesting that horizon formation in the bulk should arise. In this paper, we extend the holographic Lindblad prescription to a non-Markovian setting and apply it to JT gravity coupled to a scalar field. Using numerical simulations in the semiclassical and high-temperature regime, we demonstrate the dynamical formation of black holes.

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arXiv2025

Work distribution and fluctuation theorem in AdS/CFT

From the AdS/CFT dictionary, we derive a bulk dual of the work distribution defined by the two-point measurement on the boundary, yielding a bulk formulation of the Tasaki-Crooks fluctuation theorem. We argue that this does not merely supply a holographic prescription for the work distribution; it encodes the mean energy change and fluctuations of bulk real-time dynamics associated with the two-point measurement.

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arXiv2025

Lindblad dynamics in holography

We develop, in the AdS/CFT correspondence, a method to compute correlation functions when the CFT is governed by the Lindblad equation for open quantum systems, via the AdS theory. Using a simple example in AdS$_3$/CFT$_2$, we demonstrate that the predictions of the AdS theory based on our method match the direct computations in the dual CFT. We also briefly discuss the relaxation problem and the holographic entropy in this example.

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arXiv2024

Heat and work in black hole thermodynamics via holography

We propose a formulation of black hole thermodynamics that incorporates the notions of heat and work, based on the thermodynamics in quantum theory and the AdS/CFT correspondence. First, for coupled holographic CFTs, we define a coarse-graining procedure adopting the principle of maximum entropy. Employing this approach, when the system is divided into a target system and thermal baths, we formulate the first and second laws, as well as the fundamental thermodynamic relation. Then, by translating the resulting thermodynamics into the AdS gravity language, we construct a thermodynamic framework for composite black hole systems that encompasses both heat and work. This formulation relies on holography, but not on energy conditions on the gravity side. We also argue that the second law serves as a necessary criterion for the UV completeness of gravitational theories.

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arXiv2024

Machine-learning emergent spacetime from linear response in future tabletop quantum gravity experiments

We introduce a novel interpretable Neural Network (NN) model designed to perform precision bulk reconstruction under the AdS/CFT correspondence. According to the correspondence, a specific condensed matter system on a ring is holographically equivalent to a gravitational system on a bulk disk, through which tabletop quantum gravity experiments may be possible as reported in arXiv:2211.13863. The purpose of this paper is to reconstruct a higher-dimensional gravity metric from the condensed matter system data via machine learning using the NN. Our machine reads spatially and temporarily inhomogeneous linear response data of the condensed matter system, and incorporates a novel layer that implements the Runge-Kutta method to achieve better numerical control. We confirm that our machine can let a higher-dimensional gravity metric be automatically emergent as its interpretable weights, using a linear response of the condensed matter system as data, through supervised machine learning. The developed method could serve as a foundation for generic bulk reconstruction, i.e., a practical solution to the AdS/CFT correspondence, and would be implemented in future tabletop quantum gravity experiments.

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arXiv2024

Coarse-graining black holes out of equilibrium with boundary observables on time slice

In black hole thermodynamics, defining coarse-grained entropy for dynamical black holes has long been a challenge, and various proposals, such as generalized entropy, have been explored. Guided by the AdS/CFT, we introduce a new definition of coarse-grained entropy for a dynamical black hole in Lorentzian Einstein gravity. On each time slice, this entropy is defined as the horizon area of an auxiliary Euclidean black hole that shares the same mass, (angular) momenta, and asymptotic normalizable matter modes with the original Lorentzian solution. The entropy is shown to satisfy a generalized first law and, through holography, the second law as well. Furthermore, by applying this thermodynamics to several Vaidya models in AdS and flat spacetime, we discover a connection between the second law and the null energy condition.

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arXiv2023

Spacetime-Localized Response in Quantum Critical Spin Systems: Insights from Holography

According to the AdS/CFT correspondence, certain quantum many-body systems in $d$-dimensions are equivalent to gravitational theories in $(d+1)$-dimensional asymptotically AdS spacetimes. When a massless particle is sent from the AdS boundary to the bulk curved spacetime, it reaches another point of the boundary after a time lag. In the dual quantum system, it should appear as if quasiparticles have been transferred between two separated points. We theoretically demonstrate that this phenomenon, which we call "spacetime-localized response," is actually observed in the dynamics of the one-dimensional transverse-field Ising model near the quantum critical point. This result suggests that, if we can realize a holographic spin system in a laboratory, the experimental probing of the emergent extra-dimension is possible by applying a designed stimulus to a quantum many-body system, which is holographically equivalent to sending a massless particle through the higher-dimensional curved bulk geometry. We also discuss possible experimental realizations using Rydberg atoms in an optical tweezers array.

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arXiv2023

Shooting null geodesics into holographic spacetimes

We find, in the AdS/CFT, a source on the boundary which generates one wave packet drawing a null geodesic inside the bulk. Once such a wave packet dives into the bulk, it comes back to the boundary after a specific time, at which the expectation value of the corresponding boundary operator finally stands up. Since this behavior strongly reflects the existence of the holographic spacetime, our technique will be helpful in identifying holographic materials.

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arXiv2023

Bulk reconstruction of AdS$_{d+1}$ metrics and developing kinematic space

The metrics of the global, Poincaré, and Rindler AdS$_{d+1}$ are explicitly reconstructed with given lightcone cuts. We first compute the metric up to a conformal factor with the lightcone cuts method introduced by Engelhardt and Horowitz. While a general prescription to determine the conformal factor is not known, we recover the factor by identifying the causal information surfaces from the lightcone cuts and finding that they are minimal. In addition, we propose a new type of kinematic space as the space of minimal surfaces in AdS$_{d+1}$, where a metric is introduced as a generalization of the case of $d=2$. This metric defines the set of bulk points, which is equivalent to that of lightcone cuts. Some other properties are also studied towards establishing a reconstruction procedure for general bulk metrics.

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arXiv2022

Spacetime-emergent ring toward tabletop quantum gravity experiments

We propose a way to discover, in tabletop experiments, spacetime-emergent materials, that is, materials holographically dual to higher-dimensional quantum gravity systems under the AdS/CFT correspondence. The emergence of the holographic spacetime is verified by a mathematical imaging transform of the response function on the material. We consider theories on a 1-dimensional ring-shaped material, and compute the response to a scalar source locally put at a point on the ring. When the theory on the material has a gravity dual, the imaging in the low temperature phase exhibits a distinct difference from the ordinary materials: the spacetime-emergent material can look into the holographically emergent higher-dimensional curved spacetime and provides an image as if a wave had propagated there. Therefore the image is an experimental signature of the spacetime emergence. We also estimate temperature, ring size and source frequency usable in experiments, with an example of a quantum critical material, TlCuCl$_3$.

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arXiv2022

Generating string field theory solutions with matter operators from $KBc$ algebra

The $KBc$ algebra is a subalgebra that has been used to construct classical solutions in Witten's open string field theory, such as the tachyon vacuum solution. The main purpose of this paper is to give various operator sets that satisfy the $KBc$ algebra. In addition, since those sets can contain matter operators arbitrarily, we can reproduce the KOS and the Erler-Maccaferri solutions. Starting with a single D-brane solution on the tachyon vacuum, we replace the original $KBc$ in it with an appropriate set to generate each of the above solutions. Thus, it is expected that the $KBc$ algebra, combined with the single D-brane solution, leads to a more unified description of classical solutions.

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arXiv2022

Light-cone cuts and hole-ography: explicit reconstruction of bulk metrics

In this paper, the two reconstruction methods, light-cone cuts method and hole-ography, are combined to provide complete bulk metrics of locally AdS$_3$ static spacetimes. As examples, our method is applied to the geometries of pure AdS$_3$, AdS$_3$ soliton, and BTZ black hole, and we see them successfully reconstructed. The light-cone cuts method is known to have difficulty in obtaining conformal factors, while the hole-ography in describing temporal components. Combining the two methods, we overcome the disadvantages and give complete metrics for a class of holographic theories such that entanglement wedge and causal wedge coincide. Light-cone cuts are identified by entanglement entropy in our method. We expect our study to lead to the discovery of a universal relation between the two methods, by which the combination would be applied to more generic cases.

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arXiv2021

Interior Product, Lie Derivative and Wilson Line in the $KBc$ Subsector of Open String Field Theory

The open string field theory of Witten (SFT) has a close formal similarity with Chern-Simons theory in three dimensions. This similarity is due to the fact that the former theory has concepts corresponding to forms, exterior derivative, wedge product and integration over the manifold. In this paper, we introduce the interior product and the Lie derivative in the $KBc$ subsector of SFT. The interior product in SFT is specified by a two-component "tangent vector" and lowers the ghost number by one (like the ordinary interior product maps a $p$-form to $(p-1)$-form). The Lie derivative in SFT is defined as the anti-commutator of the interior product and the BRST operator. The important property of these two operations is that they respect the $KBc$ algebra. Deforming the original $(K,B,c)$ by using the Lie derivative, we can consider an infinite copies of the $KBc$ algebra, which we call the $KBc$ manifold. As an application, we construct the Wilson line on the manifold, which could play a role in reproducing degenerate fluctuation modes around a multi-brane solution.

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