Searcharxiv⌕ Search

arXiv subjects

Masakatsu Kenmoku

Publications and source records attributed to Masakatsu Kenmoku.

15 recordsLinked to original sources
arXiv2026

Covariant Energy Momentum Tensor in General Relativity by Generalized Canonical Method

Defining a complete and covariant energy-momentum tensor in general relativity is a longstanding issue of concern. A widely attempted approach is to define it as a pseudo-tensor in an asymptotic Lorentz system. In this paper, we present a complete covariant definition of the gravitational energy-momentum tensor in the generalized canonical form. The key is incorporate higher-order differential terms of the metric tensor into the gravitational action in order to derive the energy-momentum tensor consistently. This completely covariant form ensures that the gravitational energy is correctly obtained in any coordinate system, including polar coordinates and asymptotic Lorentz systems.

gr-qc↗
arXiv2025

Singularities of Magnetic Monopoles for Dirac and 't Hooft-Polyakov Theories by Pre-potential Method

The magnetic monopole is one of the important problems in the early stage of universe as well as observations and experiments on Earth. We study the existence or non-existence of the Dirac and the 't Hooft-Polyakov magnetic monopole theories using the pre-potential $\boldsymbol{C}$, which is defined to derive the vector potential by the curl operation as $\boldsymbol{A}=\nabla \times \boldsymbol{C}$ . We assert that the magnetic singularity exists for the 't Hooft-Polyakov monopole in SO(3) gauge theory, as well as for the Dirac monopole in U(1) gauge theory. The regularization method confirms our assertion.

hep-th↗
arXiv2019

Bargmann-Wigner Equations, Fermion-Boson Correspondence and Superradiant Problem in Curved Spacetime

Bargmann-Wigner equations and their solutions are studied in (3+1)-dimensional curved spacetime. Fermion-Boson correspondence for bi-spinor case is studied through the Bargmann-Wigner equations and solutions over curved spacetime. As an application to scattering phenomena of massive Fermions and Bosons on the rotating black holes, the superradiance with negative energy $(ω<0)$ and positive effective energy in co-rotating coordinate system near horizon $(ω-mΩ_{H}>0)$ is possible to occur as stable physical states in Kerr spacetime.

gr-qc↗
arXiv2016

Zero, Normal and Super-radiant Modes for Scalar and Spinor Fields in Kerr-anti de Sitter Spacetime

Zero and normal modes for scalar and spinor fields in Kerr-anti de Sitter spacetime are studied as bound state problem with Dirichlet and Neumann boundary conditions. Zero mode is defined as the momentum near the horizon to be zero: $p_{\rm H}=ω-Ω_{\rm H}m=0$, and is shown not to exist as physical state for both scalar and spinor fields. Physical normal modes satisfy the spectrum condition $p_{\rm H}>0$ as a result of non-existence of zero mode and the analyticity with respect to rotation parameter $a$ of Kerr-anti de Sitter black hole. Comments on the super-radiant modes and the thermodynamics of black hole are given in relation to the spectrum condition for normal modes. Preliminary numerical analysis on normal modes is presented.

gr-qc↗
arXiv2015

Bargmann-Wigner Formulation and Superradiance Problem of Bosons and Fermions in Kerr Space-time

The superradiance phenomena of massive bosons and fermions in the Kerr spacetime are studied in the Bargmann-Wigner formulation. In case of bi-spinor, the four independent components spinors correspond to the four bosonic freedom: one scalar and three vectors uniquely. The consistent description of the Bargmann-Wigner equations between fermions and bosons shows that the superradiance of the type with positive energy $(0<ω)$ and negative momentum near horizon $(p_{\rm H}<0)$ is shown not to occur. On the other hand, the superradiance of the type with negative energy $(ω<0)$ and positive momentum near horizon $(0<p_{\rm H})$ is still possible for both scalar bosons and spinor fermions.

gr-qc↗
arXiv2012

Superradiance Problem of Bosons and Fermions for Rotating Black Holes in Bargmann-Wigner Formulation

Bargmann-Wigner equations are formulated to represent bosonic fields in terms of fermionic fields in curved spacetime. The superradiance phenomena of bosons and fermions in rotating black hole spacetime are studied in the Bargmann-Wigner formulation. As a result of the consistent description between scalar bosons and spinor fermions, superradiance phenomena of the type of positive frequency $(0<ω)$ and negative momentum near horizon $(p_{H}<0)$ are shown not to occur.

gr-qc↗
arXiv2011

Young's Double Slit Experiment in Quantum Field Theory

Young's double slit experiment is formulated in the framework of canonical quantum field theory in view of the modern quantum optics. We adopt quantum scalar fields instead of quantum electromagnetic fields ignoring the vector freedom in gauge theory. The double slit state is introduced in Fock space corresponding to experimental setup. As observables, expectation values of energy density and positive frequency part of current with respect to the double slit state are calculated which give the interference term. Classical wave states are realized by coherent double slit states in Fock space which connect quantum particle states with classical wave states systematically. In case of incoherent sources, the interference term vanishes by averaging random phase angles as expected.

quant-ph↗
arXiv2009

Normal Modes, Quasi-normal Modes and Super-radiant Modes for Scalar Fields in Kerr anti-de Sitter Spacetime

Normal modes, quasi-normal modes and super-radiant modes are studied to clarify the total dynamics for complex scalar fields in Kerr anti-de Sitter black hole spacetime. Orthonormal relations and quasi-orthonormal relations are obtained for normal modes and quasi-normal modes. Mode expansions are done and the conserved quantities are studied. Any modes are shown to be separated into two groups, physical modes and unphysical modes, by the zero mode line. Zero modes themselves do not exist as normalizable modes with the correct boundary condition. The allowed physical modes exclude the super-radiant instability modes in rotating black hole spacetime. The result is consistent with the co-rotating frame consideration.

gr-qc↗
arXiv2008

Eigenvalue Problem of Scalar Fields in BTZ Black Hole Spacetime

We studied the eigenvalue problem of scalar fields in the (2+1)-dimensional BTZ black hole spacetime. The Dirichlet boundary condition at infinity and the Dirichlet or the Neumann boundary condition at the horizon are imposed. Eigenvalues for normal modes are characterized by the principal quantum number $(0<n)$ and the azimuthal quantum number $(-\infty<m< \infty)$. Effects to eigenvalues of the black hole rotation and of the scalar field mass are studied explicitly. Relation of the black hole rotation to the super-radiant instability is discussed.

gr-qc↗
arXiv2006

Generalized Area Law under Multi-parameter Rotating Black Hole Spacetime

We study the statistical mechanics for quantum scalar fields under the multi-parameter rotating black hole spacetime in arbitrary D dimensions. The method of analysis is general in the sense that the metric does not depend on the explicit black hole solutions. The generalized Stefan-Boltzmann's law for the scalar field is derived by considering the allowed energy region properly. Then the generalized area law for the scalar field entropy is derived by introducing the invariant regularization parameter in the Rindler spacetime. The derived area law is applied to Kerr-AdS black holes in four and five dimensions. Thermodynamic implication is also discussed.

gr-qc↗
arXiv2000

de Broglie-Bohm Interpretatin for Analytic Solutions of The Wheeler-DeWitt Equation in Spherically Symmetric Space-time

We discuss the implications of a wave function for quantum gravity, which involves nothing but 3-dimensional geometries as arguments and is invariant under general coordinate transformations. We derive an analytic wave function from the Wheeler-DeWitt equation for spherically symmetric space-time with the coordinate system arbitrary. The de Broglie-Bohm interpretation of quantum mechanics is applied to the wave function. In this interpretation, deterministic dynamics can be yielded from a wave function in fully quantum regions as well as in semiclassical ones. By introducing a coordinate system additionally, we obtain a cosmological black hole picture in compensation for the loss of general covariance. Our analysis shows that the de Broglie-Bohm interpretation gives quantum gravity an appropriate prescription to introduce coordinate systems naturally and extract information from a wave function as a result of breaking general covariance.

gr-qc↗
arXiv1998

de Broglie-Bohm interpretation for wave function of Reissner-Nordstrom-de Sitter black hole

We study the canonical quantum theory of the Reissner-Nordstrom-de Sitter black hole(RNdS). We obtain an exact general solution of the Wheeler-DeWitt equation for the spherically symmetric geometry with electro-magnetic field. We investigate the wave function form a viewpoint of the de Broglie-Bohm interpretation. The de Broglie-Bohm interpretation introduces a rigid trajectory on the minisuperspace without assuming an outside observer or causing collapse of the wave function. In our analysis, we obtain the boundary condition for the wave function which corresponds to the classical RNdS black hole and describe the quantum fluctuations near the horizons quantitatively.

gr-qc↗
arXiv1994

Gravitational Force by Point Particle in Static Einstein Universe

The gravitaional force produced by a point particle, like the sun, in the background of the static Einstein universe is studied. Both the approximate solution in the weak field limit and exact solution are obtained. The main properties of the solution are {\it i}) near the point particle, the metric approaches the Schwarzschild one and the radius of its singularity becomes larger than that of the Schwarzschild singularity, {\it ii}) far from the point particle, the metric approaches the static Einstein closed universe. The maximum length of the equator of the universe becomes smaller than that of the static Einstein universe due to the existence of the point particle. These properties show the strong correlation betweem the particle and the universe.

gr-qc↗
arXiv1992

Generalized Einstein Theory on Solar and Galactic Scales

We study a generalized Einstein theory with the following two criteria:{\it i}) on the solar scale, it must be consistent with the classical tests of general relativity, {\it ii}) on the galactic scale, the gravitational potential is a sum of Newtonian and Yukawa potentials so that it may explain the flat rotation curves of spiral galaxies. Under these criteria, we find that such a generalized Einstein action must include at least one scalar field and one vector field as well as the quadratic term of the scalar curvature.

astro-ph↗