Chameleon scalar fields in relativistic gravitational backgrounds (2009)
Tsujikawa, Shinji, Tamaki, Takashi, Tavakol, Reza
We study the field profile of a scalar field $\phi$ that couples to a matter fluid (dubbed a chameleon field) in the relativistic gravitational background of a spherically symmetric spacetime....
Black hole entropy for the general area spectrum (2008)
We consider the possibility that the horizon area is expressed by the general area spectrum in loop quantum gravity and calculate the black hole entropy by counting the degrees of freedom in...
Revisiting chameleon gravity - thin-shells and no-shells with appropriate boundary conditions (2008)
Tamaki, Takashi, Tsujikawa, Shinji
We derive analytic solutions of a chameleon scalar field $\phi$ that couples to a non-relativistic matter in the weak gravitational background of a spherically symmetric body, paying particular...
Post-Newtonian parameters in the tensor-vector-scalar theory (2008)
We investigate post-Newtonian parameters in the tensor-vector-scalar (TeVeS) theory in a general setting while previous researches have been restricted to spherically symmetric cases. Based on the...
Non-Abelian Black Holes in Brans-Dicke Theory (2007)
We find a black hole solution with non-Abelian field in Brans-Dicke theory. It is an extension of non-Abelian black hole in general relativity. We discuss two non-Abelian fields: "SU(2)"...
Generic features of Einstein-Aether black holes (2007)
Tamaki, Takashi, Miyamoto, Umpei
We reconsider spherically symmetric black hole solutions in Einstein-Aether theory with the condition that this theory has identical PPN parameters as those for general relativity, which is the main...
Considering boundary conditions for black hole entropy in loop quantum gravity (2007)
We argue for black hole entropy in loop quantum gravity (LQG) by taking into account the interpretation that there is no other side of the horizon. This gives new values for the Barbero-Immirzi...
Ambiguity of black hole entropy in loop quantum gravity (2005)
Tamaki, Takashi, Nomura, Hidefumi
We reexmine some proposals of black hole entropy in loop quantum gravity (LQG) and consider a new possible choice of the Immirzi parameter which has not been pointed out so far. We also discuss that...
Continuous area spectrum in regular black hole (2005)
Nomura, Hidefumi, Tamaki, Takashi
We investigate highly damped quasinormal modes of regular black hole coupled to nonlinear electrodynamics. Using the WKB approximation combined with complex-integration technique, we show that the...
The universal area spectrum in single-horizon black holes (2004)
Tamaki, Takashi, Nomura, Hidefumi
We investigate highly damped quasinormal mode of single-horizon black holes motivated by its relation to the loop quantum gravity. Using the WKB approximation, we show that the real part of the...
Radionic Non-uniform Stable Black Strings (2003)
Tamaki, Takashi, Kanno, Sugumi, Soda, Jiro
Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of black strings. The stability of...
Radionic Non-uniform Black Strings --short version-- (2003)
Tamaki, Takashi, Kanno, Sugumi, Soda, Jiro
Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of black strings. The stability of...
Black hole solutions coupled to Born-Infeld electrodynamics with derivative corrections (2003)
We investigate black hole solutions in the Einstein-Born-Infeld system. We clarify the role played by derivative corrections to the Born-Infeld (BI) action. The qulitative differences from the case...
Properties of global monopoles with an event horizon (2003)
Tamaki, Takashi, Sakai, Nobuyuki
We investigate the properties of global monopoles with an event horizon. We find that there is an unstable circular orbit even if a particle does not have an angular momentum when the core mass is...
Radionic Non-uniform Black Strings (2003)
Tamaki, Takashi, Kanno, Sugumi, Soda, Jiro
Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of the black strings. From the brane...
Particle velocity in noncommutative space-time (2002)
Tamaki, Takashi, Harada, Tomohiro, Miyamoto, Umpei, Torii, Takashi
We investigate a particle velocity in the $\kappa$-Minkowski space-time, which is one of the realization of a noncommutative space-time. We emphasize that arrival time analyses by high-energy...
Thermodynamic properties of massive dilaton black holes II (2002)
We numerically reanalyze static and spherically symmetric black hole solutions in an Einstein-Maxwell-dilaton system with a dilaton potential $m_{d}^{2}\phi^{2}$. We investigate thermodynamic...
Have we already detected astrophysical symptoms of space-time noncommutativity ? (2001)
Tamaki, Takashi, Harada, Tomohiro, Miyamoto, Umpei, Torii, Takashi
We discuss astrophysical implications of $\kappa$-Minkowski space-time, in which there appears space-time noncommutativity. We first derive a velocity formula for particles based on the motion of a...
Internal structure of Skyrme black hole (2001)
Tamaki, Takashi, Maeda, Kei-ichi, Torii, Takashi
We consider the internal structure of the Skyrme black hole under a static and spherically symmetric ansatz. $@u8(Be concentrate on solutions with the node number one and with the "winding" number...
Dyonic BIon black hole in string inspired model (2001)
Tamaki, Takashi, Torii, Takashi
We construct static and spherically symmetric particle-like and black hole solutions with magnetic and/or electric charge in the Einstein-Born-Infeld-dilaton-axion system, which is a generalization...
Estimating Hawking radiation for exotic black holes (2000)
Tamaki, Takashi, Maeda, Kei-ichi
We study about an approximation method of the Hawking radiation. We analyze an massless scalar field in exotic black hole backgrounds models which have peculiar properties in black hole...
Black hole solutions in Euler-Heisenberg theory (2000)
Yajima, Hiroki, Tamaki, Takashi
We construct static and spherically symmetric black hole solutions in the Einstein-Euler-Heisenberg (EEH) system which is considered as an effective action of a superstring theory. We considered...
Gravitating BIon and BIon black hole with dilaton (2000)
Tamaki, Takashi, Torii, Takashi
We construct static and spherically symmetric particle-like and black hole solutions with magnetic or electric charge in the Einstein-Born-Infeld-dilaton system, which is a generalization of the...
The fate of Reissner-Nortstr\"{o}m black hole in the Einstein-Yang-Mills-Higgs system (1999)
Tamaki, Takashi, Maeda, Kei-ichi
We study about an evaporating process of black holes in SO(3) Einstein-Yang-Mills-Higgs system. We consider a massless scalar field which couple neither with the Yang-Mills field nor with the Higgs...
Gravitating monopole and its black hole solution in Brans-Dicke Theory (1999)
Tamaki, Takashi, Torii, Takashi, Maeda, Kei-ichi
We find a self-gravitating monopole and its black hole solution in Brans-Dicke theory. We mainly discuss the properties of these solutions in the Einstein frame and compare the solutions with those...
Non-Abelian Black Holes in Brans-Dicke Theory (1997)
Tamaki, Takashi, Torii, Takashi, Maeda, Kei-ichi
We find a black hole solution with non-Abelian field in Brans-Dicke theory. It is an extension of non-Abelian black hole in general relativity. We discuss two non-Abelian fields: "SU(2)" Yang-Mills...