arXiv subjects

Daisuke Yoshida

Publications and source records attributed to Daisuke Yoshida.

At least 19 recordsLinked to original sources

arXiv2026

Trapped Surface as a Cosmic Censor

We formulate a local geometric criterion for weak cosmic censorship in black hole overcharging and overspinning thought experiments. Under the null convergence and generic conditions, matter injection turns a horizon cross section into a closed trapped surface. Any final spacetime unable to accommodate this surface is ruled out. This trapped surface criterion excludes superextremal Reissner-Nordstr\"om, Reissner-Nordstr\"om-de Sitter, and Kerr-Newman final states, as well as Weyl-class naked singularities. Our criterion does not rely on asymptotic charges or on an extremal condition characterizing naked singularities.

gr-qc↗

arXiv2026

Charged multi-sheet wormhole solutions

We construct charged wormhole solutions with an even number of asymptotically flat regions in the four-dimensional Einstein-Maxwell-massless phantom scalar system via the Harrison transformation. The solutions are characterized by five parameters: the mass $M$, the electric charge $Q_\mathrm{e}$, the magnetic charge $Q_\mathrm{m}$, the scalar charge $P$ and the number of sheets $2n$. The regularity condition then determines the throat radius. Although the Harrison transformation directly generates the solutions only in the parameter region $Q_{\mathrm{e}}^2 + Q_{\mathrm{m}}^2 < M^2$, we show that regular solutions exist in a wider parameter region beyond this bound. In addition, we introduce a spheroidal coordinate system that covers one complete asymptotically flat region and its adjacent ones, and allows the solution to be expressed in a simple form.

gr-qc↗

arXiv2026

Rotating wormholes in five dimensions with equal angular momenta: large asymmetry regime

We clarify the relationship between rotation and the energy condition for stationary rotating wormhole solutions of the Einstein equations coupled to a phantom field in five-dimensional spacetime with equal angular momenta, particularly with large asymmetry between the two sides. It was shown by Dzhunushaliev et al. that the violation of the null energy condition can become arbitrarily small due to rotation. We find that the degree of violation of the null energy condition is essentially determined by the angular momentum and shows little dependence on asymmetry, that is, the mass difference between the two asymptotic regions. We also discuss the relation between the wormhole spacetime and the Myers-Perry black hole. We find that the geometry asymptotes to the extremal Myers-Perry spacetime in the limit of large angular momentum, while the non-extremal black hole geometry cannot be reproduced in any limit.

gr-qc↗

arXiv2026

Assessment of Display Performance and Comparative Evaluation of Web Map Libraries for Extensive 3D Geospatial Data

Large-scale 3D geospatial data visualization has become increasingly critical for the development of the digital society infrastructure in Japan. This study conducted a comprehensive performance evaluation of two major WebGL-based web mapping libraries, CesiumJS and MapLibre GL JS, using large-scale 3D point-cloud data from the VIRTUAL SHIZUOKA and PLATEAU building models. The research employs standardized 3D Tiles 1.1, and Mapbox Vector Tiles (MVT) formats, comparing performance across different data scales (2nd and 3rd grid levels) using Core Web Vitals metrics, including First Contentful Paint (FCP), Largest Contentful Paint (LCP), Speed Index, Total Blocking Time (TBT), and Cumulative Layout Shift (CLS). The results demonstrate that MVT-based building visualization with MapLibre GL JS achieves optimal performance (FCP 0.8s, TBT 0ms), whereas MapLibre GL JS combined with deck.gl shows superior performance for large-scale point cloud processing (TBT: 3ms, CesiumJS: 21,357ms). This study provides data-driven selection guidelines for appropriate technology choices according to use cases, establishing reproducible performance evaluation frameworks for 3D web mapping technologies during the WebGPU and OGC 3D Tiles 1.1 standardization era.

cs.CY↗

arXiv2026

Dynamical Formation of Self-Similar Wormholes

We study spherically symmetric, self-similar wormhole solutions supported by colliding streams of negative-energy null dust, and their dynamical formation. Under the assumption of self-similarity, the Einstein equations reduce to a system of ordinary differential equations, which we solve numerically under boundary conditions enforcing the existence of a minimal areal radius (the throat) on constant-time hypersurfaces. For a sufficiently large throat radius, the resulting geometries remain regular at both spatial and future null infinity, while a singularity is retained in the past direction. We then construct a dynamical formation scenario by patching together three regions: a Schwarzschild black hole, negative-energy Vaidya spacetimes, and the self-similar wormhole geometry. These regions are joined across null shells using the Barrabes--Israel formalism, which provides explicit relations among the throat radius, the black hole's mass and the energy injection by the shell, demonstrating that an initial black hole can evolve into a wormhole. Our analysis generalizes the formation model for static wormhole solutions proposed by Hayward and Koyama in 2004 to non-static wormhole solutions, offering a novel perspective on the formation of regular traversable wormholes.

gr-qc↗

arXiv2025

Wormholes as perturbations of near-horizon black hole geometries: no-go theorems within effective field theories

We reformulate the construction of wormhole solutions as perturbations around near-horizon geometries of near-extremal Reissner-Nordstr\"{o}m black holes in four dimensions and equal-angular-momenta Myers-Perry black holes in five dimensions. When the negative Casimir energy is taken as the source, this framework reduces to the Maldacena-Milekhin-Popov construction for magnetically charged wormholes. We then show that, in contrast, such perturbative constructions cannot be realized within the effective field theory approach to higher-derivative corrections. Remarkably, this conclusion holds irrespective of the specific form of the correction terms. The key observation is that the enhanced symmetries in the near-horizon region severely constrain the effective energy-momentum tensor near the throat. This prevents the formation of the traversable throat structure. Our analysis therefore establishes no-go theorems: traversable wormholes cannot arise perturbatively from Reissner-Nordstr\"{o}m or Myers-Perry black holes in an effective field theory approach. Their realization would require either new ingredients, such as Casimir energy, or black holes with reduced symmetry.

gr-qc↗

arXiv2025

Quantum Storage of Frequency-Multiplexed Photons Exhibiting Nonclassical Correlations with Telecom C-Band Photons

Multiplexing is essential for improving entanglement distribution rates in quantum communication. Frequency multiplexing provides a promising and scalable path toward large-capacity quantum networks. Further progress requires increasing the number of frequency modes and developing broadband photon-pair sources and quantum memories that are spectrally compatible. Here, we report the integration of a cavity-enhanced spontaneous parametric down-conversion source in the telecom C-band with a frequency-multiplexed atomic frequency comb memory. The bow-tie cavity source was simultaneously resonant at 606 nm and 1550 nm, generating non-degenerate photon pairs exhibiting a clustered frequency-comb spectrum. The atomic frequency comb memory, implemented in Praseodymium-doped Yttrium Orthosilicate crystals, provided up to 83 frequency modes with 123 MHz spacing and enabled broadband storage of 606 nm signal photons. By filtering the main cluster, we obtained $32.7 \pm 4.8$ effective modes, as confirmed from coincidence measurements. Importantly, we observed strong nonclassical correlations after storage, with cross-correlation values of $g_{s,i}^{(2)} = 8.1\pm0.7$. Our experimental results demonstrate the feasibility of integrating cavity-enhanced photon-pair sources with rare-earth-ion-doped solid-state memories. The integration reveals a high frequency multiplicity that is essential for scalable quantum networks.

quant-ph↗

arXiv2025

Apparent Horizons Associated with Dynamical Black Hole Entropy

We define entropic marginally outer trapped surfaces (E-MOTSs) as a generalization of apparent horizons. We then show that, under first-order perturbations around a stationary black hole, the dynamical black hole entropy proposed by Hollands, Wald, and Zhang, defined on a background Killing horizon, can be expressed as the Wall entropy evaluated on an E-MOTS associated with it. Our result ensures that the Hollands-Wald-Zhang entropy reduces to the standard Wald entropy in each stationary regime of a dynamical black hole, thereby reinforcing the robustness of the dynamical entropy formulation.

gr-qc↗

arXiv2025

Dynamical Formation of Charged Wormholes

We construct static, spherically symmetric, charged traversable wormhole solutions to the Einstein--Maxwell equations, supported by bidirectional (ingoing and outgoing) null dust with negative energy, and discuss a scenario for their dynamical formation from a black hole. Our solution contains a traversable throat, where the areal radius takes a minimum, although the spacetime is not asymptotically flat. In our formation scenario, the spacetime evolves sequentially from a black hole to Vaidya regions and finally to a wormhole, with each transition mediated by an impulsive null shell. We find that the radius of the wormhole throat is determined by the mass and charge of the initial black hole as well as those of the injected shell.

gr-qc↗

arXiv2025

Multi-Sheet Wormholes in the Gravitational Soliton Formalism

We analytically construct static regular solutions describing wormholes that connect multiple asymptotic regions, supported by a phantom scalar field. The solutions are static and axially symmetric, and are constructed using the gravitational soliton formalism, in which the equations of motion reduce to the Laplace equations on a two-dimensional sheet. However, the presence of multiple asymptotic regions necessitates the introduction of multiple such sheets. These sheets are appropriately cut and glued together to form a globally regular geometry. This gluing procedure represents the principal distinction from conventional Weyl-type solitonic solutions and is a characteristic feature of the wormhole geometries studied in this paper.

gr-qc↗

arXiv2025

CNN-based Image Models Verify a Hypothesis that The Writers of Cuneiform Texts Improved Their Writing Skills When Studying at the Age of Hittite Empire

A cuneiform tablet KBo 23.1 ++/KUB 30.38, which is known to represent a text of Kizzuwatna rituals, was written by two writers with almost identical content in two iterations. Unlike other cuneiform tablets that contained information such as myths, essays, or business records, the reason why ancient people left such tablets for posterity remains unclear. To study this problem, we develop a new methodology by analyzing images of a tablet quantitatively using CNN (Convolutional Neural Network)-based image models, without segmenting cuneiforms one-by-one. Our data-driven methodology implies that the writer writing the first half was a `teacher' and the other writer was a `student' who was training his skills of writing cuneiforms. This result has not been reached by classical linguistics. We also discuss related conclusions and possible further directions for applying our method and its generalizations.

cs.CL↗

arXiv2025

Consistency between Bulk and Boundary Causalities in Asymptotically Anti-de Sitter Spacetimes

We investigate the consistency between bulk and boundary causalities in static, spherically symmetric, asymptotically anti-de Sitter (AdS) spacetimes. We derive a general formula that provides sufficient conditions for time advance, where bulk propagation arrives earlier than any boundary propagation. As an application, we show that in Reissner--Nordstr\"{o}m--anti de Sitter spacetime, no geodesic satisfies the sufficient conditions for time advance even in the super-extremal case. Furthermore, we demonstrate that the Einstein--Euler--Heisenberg theory exhibits time advance when one or a linear combination of the coupling constants is positive and below an upper bound determined by the AdS length scale.

gr-qc↗

arXiv2024

The First Law and Weak Cosmic Censorship for de Sitter Black Holes

We apply Iyer-Wald's covariant phase space formalism to asymptotically de Sitter spacetimes and establish the thermodynamic first law, expressed in terms of the Abbott-Deser mass. Similar to Iyer-Wald's first law for asymptotically flat black holes, our first law applies to general asymptotically de Sitter perturbations around a Reissner-Nordstr\"{o}m-de Sitter black hole, without imposing any symmetry for the perturbations. We explicitly derive the first law up to the second order in perturbation. Additionally, we apply this first law to a thought experiment involving the overcharging of a Reissner-Nordstr\"{o}m-de Sitter black hole by injecting energy and charge sources. We find that asymptotically de Sitter black holes cannot be overcharged, provided that the null energy condition holds, thereby reinforcing the weak cosmic censorship conjecture.

gr-qc↗

arXiv2024

Removing naked singularities in static axially symmetric spacetimes by patching with the flat spacetimes

We investigate static, axially symmetric spacetimes without naked singularities that are constructed by patching Weyl class spacetimes with the flat spacetimes. Once the exterior geometry is specified, the junction conditions determine the shape of a thin shell, which is the boundary between the two patched spacetimes, and the distribution of the energy and pressure on this shell, leaving a parameter representing the shell size free. We examine the cases where the exterior of the shell is given by Curzon--Chazy or Zipoy--Voorhees spacetimes. For each case, we find a lower bound on the shell size. Additionally, we find that the weak and null energy conditions are satisfied for any shell size, while the dominant energy condition is satisfied for sufficiently large shells. These results provide concrete examples of non-singular spacetimes with non-spherically symmetric exteriors that respect the energy conditions.

gr-qc↗

arXiv2024

Loosely trapped surface for slowly rotating black hole

We construct the marginal loosely trapped surface (marginal LTS) for the Kerr spacetime with a small Kerr parameter perturbatively, where the LTS condition is saturated. An LTS is a surface that specifies the strong gravity region, which is a generalization of the photon sphere in the Schwarzschild spacetime. It turns out that there are an infinite number of marginal LTSs. At the leading order of the small Kerr parameter, all of the marginal LTSs have the same area. However, one can see that the maximal marginal LTS among them is uniquely determined at the higher order.

gr-qc↗

arXiv2024

Cutoff Scale of Quadratic Gravity from Quantum Focusing Conjecture

We derive the cutoff length scale of the quadratic gravity in $d \geq 5$ dimensional spacetime by demanding that the quantum focusing conjecture for the smeared quantum expansion holds at the classical level. The cutoff scale has different dependence on the spacetime dimension depending on the sign of the coupling constant of the quadratic gravity. We also investigate a concrete example of the 5-dimensional Schwarzschild spacetime and directly confirm that the quantum focusing conjecture holds when the quantum expansion is smeared over the scale larger than our cutoff scale.

hep-th↗

arXiv2024

Gedanken Experiments to Destroy a Black Hole by a Test Particle: Multiply Charged Black Hole with Higher Derivative Corrections

We investigate a gedanken experiment to destroy an extremally charged black hole by dropping a test particle, provided that there are multiple $U(1)$ gauge fields coupled with each other through higher derivative interactions. In the absence of higher derivative corrections, it is known that the Coulomb repulsion prevents a test particle that would break the extremal condition from falling into an extremal black hole and therefore the black hole cannot be destroyed. We extend this observation to include higher derivative corrections. Although the extremal condition is modified by the higher derivative interactions, we find that the repulsive force induced by the higher derivative couplings is responsible for preventing a test particle that would break the modified extremal condition to reach the event horizon. Thus, we confirm that the weak cosmic censorship conjecture holds for extremally charged black holes even in the presence of higher derivative corrections, as long as the test particle approximation is justified.

hep-th↗

arXiv2024

Space-division multiplexed phase compensation for quantum communication: concept and field demonstration

Phase-sensitive quantum communication has received considerable attention to overcome the distance limitation of quantum communication. A fundamental problem in phase-sensitive quantum communication is to compensate for phase drift in an optical fiber channel. A combination of time-, wavelength-, and space-division multiplexing can improve the phase stability of the optical fiber. However, the existing phase compensations have used only time- and wavelength-division multiplexing. Here, we demonstrate space-division multiplexed phase compensation in the Osaka metropolitan networks. Our compensation scheme uses two neighboring fibers, one for quantum communication and the other for sensing and compensating the phase drift. Our field investigations confirm the correlation of the phase drift patterns between the two neighboring fibers. Thanks to the correlation, our space-division multiplexed phase compensation significantly reduces the phase drift and improves the quantum bit error rate. Our phase compensation is scalable to a large number of fibers and can be implemented with simple instruments. Our study on space-multiplex phase compensation will support the field deployment of phase-sensitive quantum communication.

quant-ph↗