arXiv subjects

M. Kenmoku

Publications and source records attributed to M. Kenmoku.

12 recordsLinked to original sources

arXiv2008

Normal Modes and No Zero Mode Theorem of Scalar Fields in BTZ Black Hole Spacetime

Eigenfunctions for normal modes of scalar fields in BTZ black hole spacetime are studied. Orthonormal relations among them are derived. Quantization for scalar fields is done and particle number, energy and angular momentum are expressed by the creation and annihilation operators. Allowed physical normal mode region is studied on the basis of the no zero mode theorem. Its implication to the statistical mechanics is also studied.

gr-qc↗

arXiv2007

Solution Independent Analysis of Black Hole Entropy in Brick Wall Model

Using the brick wall regularization of 't Hooft, the entropy of non-extreme and extreme black holes is investigated in a general static, spherically symmetric spacetime. We classify the singularity in the entropy by introducing a {\it new} index $δ$ with respect to the brick wall cut-off $ε$. The leading contribution to entropy for non-extreme case $(δ\neq 0)$ is shown to satisfy the area law with quadratic divergence with respect to the invariant cut-off $ε_{\rm inv}$ while the extreme case $(δ=0)$ exhibits logarithmic divergence or constant value with respect to $ε$. The general formula is applied to Reissner-Nordström, dilaton and brane-world black holes and we obtain consistent results.

gr-qc↗

arXiv2005

Scalar Field Contribution to Rotating Black Hole Entropy

Scalar field contribution to entropy is studied in arbitrary D dimensional one parameter rotating spacetime by semiclassical method. By introducing the zenithal angle dependent cutoff parameter, the generalized area law is derived. The non-rotating limit can be taken smoothly and it yields known results. The derived area law is then applied to the Banados-Teitelboim-Zanelli (BTZ) black hole in (2+1) dimension and the Kerr-Newman black hole in (3+1) dimension. The generalized area law is reconfirmed by the Euclidean path integral method for the quantized scalar field. The scalar field mass contribution is discussed briefly.

gr-qc↗

arXiv2002

Conservation of Energy in Black Holes and in Cosmology

We first review the various definition of the total energy in the gravitational system. The naive definition has some defects, and we review how to modify the definition of the total energy. Then we explicitly demonstrate how to calculate the total energy of the system. Our example is the total energy of a black hole in the expanding closed de Sitter universe in (2+1) dimension. In general, we find that the contribution to the total energy comes only from the singularity. Then we can calculate the total energy by evaluating the contribution around the singularity.

gr-qc↗

arXiv2002

Conical Singular Solutions in (2+1)-Dimensional Gravity Employing the ADM Canonical Formalism

Topological solutions in the (2+1)-dimensional Einstein theory of gravity are studied within the ADM canonical formalism. It is found that a conical singularity appears in the closed de Sitter universe solution as a topological defect in the case of the Einstein theory with a cosmological constant. Quantum effects on the conical singularity are studied using the de Broglie-Bohm interpretation. Finite quantum tunneling effects are obtained for the closed de Sitter universe, while no quantum effects are obtained for an open universe.

gr-qc↗

arXiv2001

Classical and Quantum Solutions of 2+1 Dimensional Gravity under De Broglie-Bohm Interpretation

We have studied classical and quantum solutions of 2+1 dimensional Einstein gravity theory. Quantum theory is defined through the local conserved angular momentum and mass operators in the case of spherically symmetric space-time. The de Broglie-Bohm interpretation is applied for the wave function and we derive the differential equations for metrics. Metrics including quantum effect are obtained in solving these equations and we compare them with classical metrics. Especially the quantum effect on the closed de Sitter universe is evaluated quantitatively.

gr-qc↗

arXiv2001

On quantum analogues of p-brane black holes

In a multidimensional model with several scalar fields and an m-form we deal with classical spherically symmetric solutions with one (electric or magnetic) p-brane and Ricci-flat internal spaces and the corresponding solutions to the Wheeler--DeWitt (WDW) equation. Classical black holes are considered and their quantum analogues (e.g. for M2 and M5 extremal solutions in D =11 supergravity, electric and magnetic charges in D=4 gravity) are suggested when the curvature coupling in the WDW equation is zero.

gr-qc↗

arXiv2000

Canonical Theory of 2+1 Gravity

Recently 2+1 dimensional gravity theory, especially ${\rm AdS_3}$ has been studied extensively. It was shown to be equivalent to the 2+1 Chern-Simon theory and has been investigated to understand the black hole thermodynamics, i.e. Hawking temperature and others. The purpose of this report is to investigate the canonical formalism of the original 2+1 Einstein gravity theory instead of the Chern-Simon theory. For the spherically symmetric space-time, local conserved quantities(local mass and angular momentum) are introduced and using them canonical quantum theory is defined. Constraints are imposed on state vectors and solved analytically. The strategy to obtain the solution is followed by our previous work.

gr-qc↗

arXiv2000

The Scenario for the Astrophysics with Scalar Field and the Cosmological Constant

In order to give the standard scenario of the astrophysics, we study the Einstein theory with minimally coupled scalar field and the cosmological term by considering the scalar field as a candidate of the dark matter. We obtained the exact solution in the cosmological scale and the approximate gravitational potential in the galactic or solar scale. We find that the scalar field plays the role of the dark matter in some sense in the cosmological scale but it does not play the role of the dark matter in the galactic or solar scale within our approximation.

gr-qc↗

arXiv1997

de Broglie-Bohm Interpretation for the Wave Function of Quantum Black Holes

We study the quantum theory of the spherically symmetric black holes. The theory yields the wave function inside the apparent horizon, where the role of time and space coordinates is interchanged. The de Broglie-Bohm interpretation is applied to the wave function and then the trajectory picture on the minisuperspace is introduced in the quantum as well as the semi-classical region. Around the horizon large quantum fluctuations on the trajectories of metrics $U$ and $V$ appear in our model, where the metrics are functions of time variable $T$ and are expressed as $ds^2=-{α^2}/U dT^2 + U dR^2 + V dΩ^2$. On the trajectories, the classical relation $U=-V^{1/2}+2Gm$ holds, and the event horizon U=0 corresponds to the classical apparent horizon on $V=2Gm$. In order to investigate the quantum fluctuation near the horizon, we study a null ray on the dBB trajectory and compare it with the one in the classical black hole geometry.

gr-qc↗

arXiv1995

Classical and Quantum Solutions and the Problem of Time in $R^2$ Cosmology

We have studied various classical solutions in $R^2$ cosmology. Especially we have obtained general classical solutions in pure $R^2$\ cosmology. Even in the quantum theory, we can solve the Wheeler-DeWitt equation in pure $R^2$\ cosmology exactly. Comparing these classical and quantum solutions in $R^2$\ cosmology, we have studied the problem of time in general relativity.

gr-qc↗

arXiv1992

Rotation Curves of Spiral Galaxies and Large Scale Structure of Universe under Generalized Einstein Action

We consider an addition of the term which is a square of the scalar curvature to the Einstein-Hilbert action. Under this generalized action, we attempt to explain i) the flat rotation curves observed in spiral galaxies, which is usually attributed to the existence of dark matter, and ii) the contradicting observations of uniform cosmic microwave background and non-uniform galaxy distributions against redshift. For the former, we attain the flatness of velocities, although the magnitudes remain about half of the observations. For the latter, we obtain a solution with oscillating Hubble parameter under uniform mass distributions. This solution leads to several peaks of galaxy number counts as a function of redshift with the first peak corresponding to the Great Wall.

hep-ph↗