Takuya Maki

Bio: Takuya Maki is an academic researcher from Tokyo Metropolitan University. The author has contributed to research in topics: Black hole & Dilaton. The author has an hindex of 7, co-authored 18 publications receiving 175 citations. Previous affiliations of Takuya Maki include Japan Women's College of Physical Education & Kitasato University.

Multi-black hole solutions in cosmological Einstein-Maxwell-dilaton theory

Abstract: Adopting a simple ansatz, we find exact solutions to the Einstein-Maxwell-dilaton equations, which stand for the multi-black hole configuration with maximal charge in a cosmological metric and dilaton field background driven by a cosmological term.

Vacuum polarization around a three-dimensional black hole

Abstract: We calculate the Euclidean propagator for a conformally coupled massless scalar field in the background of the three-dimensional black hole. The expectation value in the Hartle--Hawking state is obtained in the spacetime.

Motion of test particles around a charged dilatonic black hole

Abstract: We examine motion of test particles with various masses, electric charges and dilatonic charges in a background metric and fields of a charged dilatonic black hole.

Motion of Test Particles around a Charged Dilatonic Black Hole

Abstract: We examine motion of test particles with various masses, electric charges and dilatonic charges in a background metric and fields of a charged dilatonic black hole.

Moyal Quantization for Constrained System

Abstract: We study Moyal quantization for a constrained system. One of the purposes of this work is to give a proper definition of the Wigner-Weyl (WW) correspondence, which connects the Weyl symbols with the corresponding quantum operators. A Hamiltonian in terms of the Weyl symbols is different from the classical Hamiltonian for a constrained system. This difference is related to the fact that the naively constructed WW correspondence is no longer one-to-one. In the Moyal quantization, the geometrical meaning of the constraints is clear. In the proposal presented here, the second class constraints are incorporated into the definition of the WW correspondence by limiting the phase space to a hypersurface, while we assume canonical commutation relations for the phase space variables. In the case of linear constraints, we confirm that the Moyal brackets between the Weyl symbols yield the same results as those for the constrained system derived using the Dirac bracket formulation.

Eternal black holes in anti-de Sitter

Abstract: We propose a dual non-perturbative description for maximally extended Schwarzschild Anti-de-Sitter spacetimes. The description involves two copies of the conformal field theory associated to the AdS spacetime and an initial entangled state. In this context we also discuss a version of the information loss paradox and its resolution.

The (2 + 1)-dimensional black hole

Abstract: I review the classical and quantum properties of the (2 + 1)-dimensional black hole of Banados, Teitelboim and Zanelli. This solution of the Einstein field equations in three spacetime dimensions shares many of the characteristics of the Kerr black hole: it has an event horizon, an inner horizon, and an ergosphere; it occurs as an endpoint of gravitational collapse; it exhibits mass inflation; and it has a non-vanishing Hawking temperature and interesting thermodynamic properties. At the same time, its structure is simple enough to allow a number of exact computations, particularly in the quantum realm, that are impractical in 3 + 1 dimensions.

Are black holes in alternative theories serious astrophysical candidates? The Case for Einstein-Dilaton-Gauss-Bonnet black holes

Abstract: It is generally accepted that Einstein's theory will get some as yet unknown corrections, possibly large in the strong-field regime. An ideal place to look for these modifications is in the vicinities of compact objects such as black holes. Here, we study dilatonic black holes, which arise in the framework of Gauss-Bonnet couplings and one-loop corrected four-dimensional effective theory of heterotic superstrings at low energies. These are interesting objects as a prototype for alternative, yet well-behaved gravity theories: they evade the 'no-hair' theorem of general relativity but were proven to be stable against radial perturbations. We investigate the viability of these black holes as astrophysical objects and try to provide some means to distinguish them from black holes in general relativity. We start by extending previous works and establishing the stability of these black holes against axial perturbations. We then look for solutions of the field equations describing slowly rotating black holes and study geodesic motion around this geometry. Depending on the values of mass, dilaton charge, and angular momentum of the solution, one can have differences in the innermost-stable-circular-orbit location and orbital frequency, relative to black holes in general relativity. In the most favorable cases, the difference amounts tomore » a few percent. Given the current state-of-the-art, we discuss the difficulty of distinguishing the correct theory of gravity from electromagnetic observations or even with gravitational-wave detectors.« less