arXiv subjects

Yu-Ke Wang

Publications and source records attributed to Yu-Ke Wang.

2 recordsLinked to original sources

arXiv2025

Equation of the Perfect Fluid in the FRW Universe

In this paper, we study the equation of state and its properties of the perfect fluid in the $D$-dimensional FRW universe under Einstein gravity, Gauss-Bonnet gravity and Lovelock gravity. In Einstein gravity, we get the equation of state and find that it has no critical point in the $P$-$V$ diagram, but its isothermal lines have minima in the $4$-dimensional case and are always negative in higher dimensions. In Gauss-Bonnet gravity, we get the equation of state and find that it has a critical point in the $5,6,7,8$-dimensional cases with phase transitions above the critical temperature. In Lovelock gravity, we get the equation of state and conditions of the critical points. Our work shows that both the theories of gravity and the dimensions of the FRW universe affect the existence of the critical point of the perfect fluid. Interestingly, if the critical point exists, phase transition always occures above the critical temperature.

gr-qc↗

arXiv2025

Temperature of McVittie Black Holes in Cavities

In this paper, we obtain the temperature of the McVittie black hole and the charged McVittie black hole in a cavity with radius $r_c$. The cavity temperature is derived from the black hole Hawking temperature and Kodama vector by using the Tolman relation. We also obtain the cavity temperature of the de Sitter black hole and the charged de Sitter black hole respectively by setting $H^2=\Lambda/3$ from the above results, which are the same as those from the action method. By the way, we also find that the Kodama vector of the McVittie and charged McVittie black hole is just $\partial/\partial t$, which is very remarkable and interesting. It shows that this method to obtain the cavity temperature is consistent and applicable. It is obvious that this method is much easier than the action method and can be used to similar investigations. It also shows that Kodama vector is very important and useful for dynamical spacetimes.

gr-qc↗