arXiv subjects

Tetsuya Shiromizu

Publications and source records attributed to Tetsuya Shiromizu.

130 records · Page 8Linked to original sources

arXiv1995

Dynamics of Subcritical Bubbles in First Order Phase Transition

We derivate the Langevin and the Fokker-Planck equations for the radius of $O(3)$-symmetric subcritical bubbles as a phenomenological model to treat thermal fluctuation. The effect of thermal noise on subcritical bubbles is examined. We find that the fluctuation-dissipation relation holds and that in the high temperature phase the system settles down rapidly to the thermal equilibrium state even if it was in a nonequilibrium state initially. We then estimate the typical size of subcritical bubbles as well as the amplitude of fluctuations on that scale. We also discuss their implication to the electroweak phase transition.

astro-ph↗

arXiv1995

Volume Expansion Rate and The Age of The Universe

Under four assumptions such that 1) Einstein's theory of gravity is correct, 2) existence of foliation by geodesic slicing, 3) the trace of the extrinsic curvature, $K$, is negative at the present time in observed region, that is, the observed universe is now expanding, 4) the strong energy condition is satisfied, we show that $H_{v0} t_{0} \leq 1$, where $H_v \equiv - K/3$ agrees with the Hubble parameter in the case of a homogeneous and isotropic universe, and $t_0$ is the age of the Universe. If $H_{v0} t_0 > 1$ is confirmed observationally, at least one of the four assumptions is incorrect.

astro-ph↗

arXiv1995

Thermal fluctuations in electroweak phase transition

We estimate the amplitude of thermal fluctuations by calculating the typical size of subcritical bubbles in cosmological electroweak phase transition and show that this thermal fluctuation effect drastically changes dynamics of the phase transition from the ordinary first order type with supercooling. From this fact, we conclude that the standard electroweak baryogenesis scenario associated with such a first order transition does not work in the minimal standard model in certain conditions.

hep-ph↗

arXiv1994

A Cosmological Constant Limits the Size of Black Holes

In a space-time with cosmological constant $Λ>0$ and matter satisfying the dominant energy condition, the area of a black or white hole cannot exceed $4π/Λ$. This applies to event horizons where defined, i.e. in an asymptotically deSitter space-time, and to outer trapping horizons (cf. apparent horizons) in any space-time. The bound is attained if and only if the horizon is identical to that of the degenerate `Schwarzschild-deSitter' solution. This yields a topological restriction on the event horizon, namely that components whose total area exceeds $4π/Λ$ cannot merge. We discuss the conjectured isoperimetric inequality and implications for the cosmic censorship conjecture.

gr-qc↗