Koji Hashimoto

The motion of a particle near a horizon of a spherically symmetric static black hole is shown to possess a universal Lyapunov exponent of chaos bounded by its surface gravity. To probe the horizon, we introduce an electromagnetic or scalar force to the particle so that it does not fall into the horizon. There appears an unstable maximum of the total potential where the evaluated maximal Lyapunov exponent is found to be to the surface gravity of the black hole. This value is independent of the ex

In this paper, we study properties of baryons by using a holographic dual of QCD on the basis of the D4/D8-brane configuration, where baryons are described by a soliton. We first determine the asymptotic behavior of the soliton solution, which allows us to evaluate welldefined currents associated with the U(Nf)L × U(Nf)R chiral symmetry. Using the currents, we compute static quantities of baryons such as charge radii and magnetic moments, and make a quantitative test with experiments. It is emph

We present a deep neural network representation of the $\mathrm{AdS}/\mathrm{CFT}$ correspondence, and demonstrate the emergence of the bulk metric function via the learning process for given data sets of response in boundary quantum field theories. The emergent radial direction of the bulk is identified with the depth of the layers, and the network itself is interpreted as a bulk geometry. Our network provides a data-driven holographic modeling of strongly coupled systems. With a scalar ${\ensu

Quantum complexity is conjectured to probe inside of black hole horizons (or wormholes) via gauge gravity correspondence. In order to have a better understanding of this correspondence, we study time evolutions of complexities for Abelian pure gauge theories. For this purpose, we discretize the $U(1)$ gauge group as ${\mathbf{Z}}_{N}$ and also the continuum spacetime as lattice spacetime, and this enables us to define a universal gate set for these gauge theories and to evaluate time evolutions

Cosmic strings in non-abelian gauge theories naturally gain a spectrum of massless, or light, excitations arising from their embedding in color and flavor space. This opens up the possibility that colliding strings miss each other in the internal space, reducing the probability of reconnection. We study the topology of the non-abelian vortex moduli space to determine the outcome of string collision. Surprisingly we find that the probability of classical reconnection in this system remains unity,

We apply the relation between deep learning (DL) and the $\mathrm{AdS}/\mathrm{CFT}$ correspondence to a holographic model of QCD. Using lattice QCD data of the chiral condensate at a finite temperature as our training data, the deep learning procedure holographically determines an emergent bulk metric as neural network weights. The emergent bulk metric is found to have both a black hole horizon and a finite-height IR wall, so it shares both the confining and the deconfining phases, signaling th

Using holographic QCD based on D4-branes and D8-anti-D8-branes, we have computed couplings of glueballs to light mesons. We describe glueball decay by explicitly calculating its decay widths and branching ratios. Interestingly, while glueballs remain less well understood both theoretically and experimentally, our results are found to be consistent with the experimental data for the scalar glueball candidate ${f}_{0}(1500)$. More generally, holographic QCD predicts that decay of any glueball to $

We study an exotic state which is localized only at an intersection of edges of a topological material. This ``edge-of-edge'' state is shown to exist generically. We construct explicitly generic edge-of-edge states in five-dimensional Weyl semimetals and their dimensional reductions, such as four-dimensional topological insulators of class A and three-dimensional chiral topological insulators of class AIII. The existence of the edge-of-edge state is due to a topological charge of the edge states

A bstract Recently, Krylov complexity was proposed as a measure of complexity and chaoticity of quantum systems. We consider the stadium billiard as a typical example of the quantum mechanical system obtained by quantizing a classically chaotic system, and numerically evaluate Krylov complexity for operators and states. Despite no exponential growth of the Krylov complexity, we find a clear correlation between variances of Lanczos coefficients and classical Lyapunov exponents, and also a correla

We provide a deep Boltzmann machine (DBM) for the $\mathrm{AdS}/\mathrm{CFT}$ correspondence. Under the philosophy that the bulk spacetime is a neural network, we give a dictionary between those, and obtain a restricted DBM as a discretized bulk scalar field theory in curved geometries. The probability distribution as training data is the generating functional of the boundary quantum field theory, and it trains neural network weights which are the metric of the bulk geometry. The deepest layer i

Thermal states in some quantum field theories (QFTs) correspond to black holes in asymptotically AdS spacetime in the $\mathrm{AdS}/\mathrm{CFT}$ correspondence. We propose a direct procedure to construct holographic images of the black hole in the bulk from a given response function of the QFT on the boundary. The response function with respect to an external source corresponds to the asymptotic data of the bulk field generated by the source on the AdS boundary. According to the wave optics, we

Clarifying conditions for the existence of a gravitational picture for a given quantum field theory (QFT) is one of the fundamental problems in the AdS/CFT correspondence. We propose a direct way to demonstrate the existence of the dual black holes: imaging an Einstein ring. We consider a response function of the thermal QFT on a two-dimensional sphere under a time-periodic localized source. The dual gravity picture, if it exists, is a black hole in an asymptotic global AdS_{4} and a bulk probe

Using a distributed multimedia system that can integrate various real-time and nonreal-time media data, when the system users communicate with each other by real-time audio video data, the system must guarantee end-to-end QoS (quality of service) according to requirements from the system users and available resources. If the system can dynamically use translator or mixer functions defined by RTP, more flexible peer-to-peer communication is realized. In this paper, we design a new middleware syst