Zobrazeno 1 - 10
of 116
pro vyhledávání: '"Miyamoto, Umpei"'
Autor:
Hioki, Kenta, Miyamoto, Umpei
We present a method for determining the physical parameters of a Kerr-Newman black hole through shadow observation. In a system comprising a Kerr-Newman black hole, an observer, and a light source, the relevant parameters are mass $M$, specific angul
Externí odkaz:
http://arxiv.org/abs/2411.08486
Autor:
Hioki, Kenta, Miyamoto, Umpei
We propose a new method to determine the physical parameters of Kerr black holes (namely, specific angular momentum $a$, inclination angle $i$, and distance $D$ from an observer) only from the shadow's information such as the size and shape. Key poin
Externí odkaz:
http://arxiv.org/abs/2311.16802
Stability of hypersurfaces of constant mean curvature with free boundary in two parallel hyperplanes
Autor:
Koiso, Miyuki, Miyamoto, Umpei
Publikováno v:
JSIAM Letters, vol. 15, pp. 9-12 (2023)
Surfaces with constant mean curvature (CMC) are critical points of the area with volume constraint. They serve as a mathematical model of surfaces of soap bubbles and tiny liquid drops. CMC surfaces are said to be stable if the second variation of th
Externí odkaz:
http://arxiv.org/abs/2306.12211
Autor:
Hioki, Kenta, Miyamoto, Umpei
We revisit the classic system of a spherically symmetric black hole in general relativity (i.e., a Schwarzschild black hole) surrounded by a geometrically thin accretion disk. Our purpose is to examine whether one can determine three parameters of th
Externí odkaz:
http://arxiv.org/abs/2210.02164
Publikováno v:
Phys. Rev. D 101, 044023 (2020)
We investigate the escape of photons from the vicinity of the horizon to infinity in the Kerr-Newmann black hole spacetime. We assume that a light source is at rest in a locally nonrotating frame and photons are emitted isotropically. Then, we evalua
Externí odkaz:
http://arxiv.org/abs/1910.01528
Autor:
Koiso, Miyuki, Miyamoto, Umpei
Publikováno v:
Japan J. Indust. Appl. Math. (2023)
Static equilibrium configurations of continua supported by surface tension are given by constant mean curvature (CMC) surfaces which are critical points of a variational problem to extremize the area while keeping the volume fixed. CMC surfaces are u
Externí odkaz:
http://arxiv.org/abs/1905.01705
Autor:
Sotani, Hajime, Miyamoto, Umpei
We systematically study pulsar light curves, taking into account the special relativistic effect, i.e., the Doppler factor due to the fast spin of the neutron stars, together with the time delay, which comes from the difference of the travel times de
Externí odkaz:
http://arxiv.org/abs/1811.03702
Autor:
Sotani, Hajime, Miyamoto, Umpei
Gravitational light bending by compact stars is an important astrophysical phenomenon. The bending angle depends on the stellar compactness, which is the ratio of stellar mass $M$ to radius $R$. In this paper, we investigate the pulse profile of high
Externí odkaz:
http://arxiv.org/abs/1807.09071
Autor:
Miyamoto, Umpei
Publikováno v:
Phys. Rev. D 99, 025012 (2019)
We investigate the dynamic Casimir effect (DCE) of a $1+1$ dimensional free massless scalar field in a finite or semi-infinite cavity for which the boundary condition (BC) instantaneously changes from the Neumann to Dirichlet BC or reversely. While t
Externí odkaz:
http://arxiv.org/abs/1805.02367
Autor:
Sotani, Hajime, Miyamoto, Umpei
Publikováno v:
Phys. Rev. D 96, 104018 (2017)
In order to examine the pulse profile from a pulsar, we derive the formula for describing the flux from antipodal hot spots with any static, spherically symmetric spacetime. We find that the pulse profiles are almost independent of the gravitational
Externí odkaz:
http://arxiv.org/abs/1710.08581