arXiv subjects

Masanori Tomonaga

Publications and source records attributed to Masanori Tomonaga.

4 recordsLinked to original sources

arXiv2026

Reconstructing a large-scale matter-density contrast profile to reconcile Pantheon+ supernovae with DESI DR2 BAO in an inhomogeneous universe

The Hubble parameters measured by the DESI DR2 BAO observations show a significant discrepancy from the prediction of the standard cosmological model. This discrepancy, together with the long-discussed Hubble tension, may originate from large-scale inhomogeneities in the matter distribution. This interpretation is motivated by infrared galaxy surveys, which suggest that our galaxy resides within the $\sim300$ Mpc under-dense region known as the KBC void. In this study, we apply a linear order relation -- relating the horizon-scale Hubble parameter inferred from CMB observations and the local-scale Hubble parameter -- to the Pantheon+ Type Ia supernovae and the DESI DR2 BAO data. We show that a simple inhomogeneous cosmological model consisting of eight top-hat shells can consistently explain the Hubble parameters inferred from both observations. Based on the matter-density distribution, we also briefly discuss its possible impact on cosmological observables, including the magnitude--redshift relation, the kinematic Sunyaev--Zel'dovich effect, and the integrated Sachs--Wolfe effect.

astro-ph.CO↗

arXiv2024

Second-Order Coherence as an Indicator of Quantum Entanglement of Hawking Radiation in Moving-Mirror Models

The second-order coherence of light is a widely recognized physical quantity used to assess the quantum characteristics of light, and its properties have been extensively investigated in the field of quantum optics. Recently, it has been proposed that second-order coherence can be utilized as an indicator of quantum entanglement. In this study, we evaluated the second-order coherence in the context of the moving-mirror model, which serves as an analog model for Hawking radiation from a black hole. We discuss the relation between entanglement and the second-order coherence of Hawking radiation paying attention to the noise effect due to the thermality of Hawking radiation, which reduces the quantum correlation in the entanglement-harvesting protocol with two-qubit detectors.

quant-ph↗

arXiv2023

The gauge-invariant formulation of the local expansion rate driven by the local average density in an inhomogeneous universe

The Hubble tension casts a blight on the standard cosmology. As a possible solution to the problem, the local variation of the expansion rate has been proposed where the spatial averaging over a finite domain was introduced in order to restore the local Friedmannian behavior in an inhomogeneous cosmology. So far, however, the approaches are limited to the particular choices of the gauges, and it has been unclear whether the results are gauge-invariant. In this paper, we present the gauge-invariant formulation of the local expansion rate which is driven by the spatial average of the gauge-invariant inhomogeneous density. We show that the local cosmological parameters in the finite domain may change from the global parameters, and the relations between them are expressed by the gauge-invariant averaged density.

gr-qc↗

arXiv2022

On the gauge invariance of the locally averaged Friedmann Universe and the Hubble tension

The Hubble tension cast a blight on the standard cosmology. As a possible attitude to the problem, the local variation of the expansion rate in an inhomogeneous cosmology has been proposed where the spatial averaging over a finite domain was introduced in order to construct local Friedmann spacetime. However, it is not clear that the concept of the spatial averaging itself is gauge invariant or not. Namely the conclusion obtained by the averaging in a particular gauge is physically meaningful or not. In this paper we address this question, namely the gauge invariance of the spatial averaging in cosmology . We show that the answer is positive by studying the spatial average in the gauge-invariant cosmological perturbation theory.

gr-qc↗