Generalized holographic Ricci dark energy and generalized second law of thermodynamics in Bianchi Type I universe

Abstract

Generalized second law of thermodynamics in the Bianchi type I universe with the generalized holographic Ricci dark energy model is studied in this paper. The behavior of dark energy's equation of state parameter indicates that it is matter-like in the early time of the universe but phantom-like in the future. By analysing the evolution of the deviations of state parameter and the total pressure of the universe, we find that for an anisotropic Bianchi type I universe, it transits from a high anisotropy stage to a more homogeneous stage in the near past. Using the normal entropy given by Gibbs' law of thermodynamics, it is proved that the generalized second law of thermodynamics does not always satisfied throughout the history of the universe when we assume the universe is enclosed by the generalized Ricci scalar radius Rgr. It becomes invalid in the near past to the future, and the formation of the galaxies will be helpful in explaining such phenomenon, for that the galaxies's formation is an entropy increase process. The negative change rates of the horizon entropy and internal entropy occur in different period indicates that the influences of galaxies formation is wiped from internal to the universe's horizon.

Effects of anisotropy on the sign-changeable interacting Tsallis holographic dark energy

“…The BI metric, which includes the anisotropy of early cosmos, is written as [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103]…”

“…where A(t), B(t) and C(t) are functions of cosmic time. Hence, the FLRW metric is recovered whenever A = B = C [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103]. For this metric, i) V 3 ≡ ABC denotes the spatial volume.…”

“…It is worthwhile mentioning that the shear scalar is describable, using the average Hubble parameter, as σ 2 = σ 2 0 H 2 in which σ 2 0 is a constant [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103]. In the presence of a mutual interaction (Q) between the cosmos sectors, the continuity equation is decomposed as [76,77] ρm…”

“…Thus, a comprehensive study on the cosmic evolution should consider the anisotropy effects. The Bianchi models are some interesting attempts to model the anisotropy of the early universe [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103]. Motivated by the above arguments, we are going to study the cosmic evolution of a Bianchi type I (BI) model filled by DE and DM interacting with each other throughout a sign-changeable interaction.…”

Dark Energy Accretion onto Van der Waal’s Black Hole

“…Some methods are given to solve these problems, such as considering the holographic principle [17], anthropic principle [18], invoking an interaction between dark matter and dark energy [19] and variable cosmological constant scenario [20]. In this context, several well-known models such as phantom, quintom, Chaplygin gas, quintessence, geographic dark energy and holographic dark energy, etc., have been proposed [21,22,23,24,25,26,27,28]. The Chaplygin gas is an exotic type of fluid whose energy density ρ and pressure p fit the equation of state p = −B/ρ, where B is a positive constant [29].…”