Related papers: On phantom thermodynamics with negative temperatur…
The $P$-$V$ phase transition of the FRW (Friedmann-Robertson-Walker) universe with a perfect fluid has recently been investigated, revealing that the four critical exponents near the critical point are consistent with the values predicted…
We consider a FRW universe filled by a dark energy candidate together with other possible sources which may include the baryonic and non-baryonic matters. Thereinafter, we consider a situation in which the cosmos sectors do not interact…
We find phase transitions and critical phenomena of the FRW (Friedmann-Robertson-Walker) universe in the framework of an effective scalar-tensor theory that belongs to the Horndeski class. We identify the thermodynamic pressure (generalized…
We study thermodynamics of the apparent horizon in $F(R)$ gravity. In particular, we demonstrate that a $F(R)$ gravity model with realizing a crossing of the phantom divide can satisfy the second law of thermodynamics in the effective…
I present exact results matching Kerr-Newman Black Hole thermodynamics in the extremal limit to the two-dimensional Fermi Gas. Two dimensions are consistent with the membrane paradigm of black holes. Key in the analysis is the thermodynamic…
Although well motivated from theoretical arguments, the cosmological constant \emph{barrier}, i.e., the imposition that the equation-of-state parameter of dark energy ($\omega_x \equiv p_x/\rho_x$) is $\geq -1$, seems to introduce bias in…
Several lectures for non-experts on equilibrium and non-equilibrium kinetics in expanding universe are presented. An establishment of thermal equilibrium in the ealry universe as well as mechanisms leading to deviations from the equilibrium…
We analyze the thermodynamics of spherically symmetric thin-shell solutions to Einstein's equations, including solutions with negative interior mass. We show the inclusion of such solutions is essential for the thermodynamic consistency of…
Recently, the observed equation of state for dark energy appears to favor values below $-1$. The tendency implies that the nature of dark energy may be quite different from that of the cosmological constant. In view of the adjustment on the…
We propose a new equation of state for the Dark Energy component of the Universe. It is modeled on the equation of state $p=w(\rho-\rho_{*})$ which can describe a liquid, for example water. We show that its energy density naturally…
We study the evolution of the dark energy parameter within the scope of a spatially non-flat and isotropic Friedmann-Robertson-Walker (FRW) model filled with barotropic fluid and bulk viscous stresses. We have obtained cosmological…
We show that states of macroscopic systems with purported absolute negative temperatures are not stable under small, yet arbitrary, perturbations. We prove the previous statement using the fact that, in equilibrium, the entropy takes its…
We investigate the interaction between dark energy and dark matter in the framework of irreversible thermodynamics of open systems with matter creation/annihilation. We consider dark energy and dark matter as an interacting two component…
In his 2005 review, Gravity and the Thermodynamics of Horizons, Paddy suggested that a vacuum in thermal equilibrium with a bath of radiation should have a gradually diminishing energy. We work through the consequences of this scenario, and…
We quantize a scalar field at finite temperature T in the background of a classical black hole, adopting 't Hooft's ``brick wall'' model with generic mixed boundary conditions at the brick wall boundary. We first focus on the exactly…
A model consisting of quintessence scalar field interacting with cold dark matter is considered. Conditions required to reach $w_d=-1$ are discussed. It is shown that depending on the potential considered for the quintessence, reaching the…
We examine phantom dark energy models produced by a field with a negative kinetic term and a potential that satisfies the slow roll conditions: [(1/V)(dV/dphi)]^2 << 1 and (1/V)(d^2 V/dphi^2) << 1. Such models provide a natural mechanism to…
We focus on the thermodynamic behavior of Polytropic gas as a candidate for dark energy. We use the general arguments of thermodynamics to investigate its properties and behavior. We find that a Polytropic gas may exhibit the dark energy…
This work examines some aspects related to the existence of negative mass. The requirement for the partition function to converge leads to two distinct approaches. Initially, convergence is achieved by assuming a negative absolute…
A possible candidate for the present accelerated expansion of the Universe is ''phantom energy'', which possesses an equation of state of the form $\omega\equiv p/\rho<-1$, consequently violating the null energy condition. As this is the…