Thermodynamical Description of Modified Generalized Chaplygin Gas Model of Dark Energy

Abstract

We consider a universe filled by a modified generalized Chaplygin gas together with a pressureless dark matter component. We get a thermodynamical interpretation for the modified generalized Chaplygin gas confined to the apparent horizon of FRW universe, whiles dark sectors do not interact with each other. Thereinafter, by taking into account a mutual interaction between the dark sectors of the cosmos, we find a thermodynamical interpretation for interacting modified generalized Chaplygin gas. Additionally, probable relation between the thermal fluctuations of the system and the assumed mutual interaction is investigated. Finally, we show that if one wants to solve the coincidence problem by using this mutual interaction, then the coupling constants of the interaction will be constrained. The corresponding constraint is also addressed. Moreover, the thermodynamic interpretation of using either a generalized Chaplygin gas or a Chaplygin gas to describe dark energy is also addressed throughout the paper.

Thermodynamic descriptions of polytropic gas and its viscous type as dark energy candidates

“…Now, by inserting Eqs. (16), (24) and (31) into this equation one may find a relation for Q up to the first order of fluctuations. Roughly speaking, this relation helps us get a thermodynamic interpretation for the mutual interaction between the dark sectors of cosmos, up to the first order of fluctuations.…”

“…Moreover, if one only considers the S 0 D and S 1 D terms she can find a relation for the mutual interaction between dark sectors up to the first order of thermal fluctuations, by inserting Eqs. (46), (43), (36) and (48) into relation [24][25][26][27][28]31]…”

“…where b 1 and b 2 are coupling constants of interaction. In order to solve the coincidence problem, interaction term should satisfy the Q > 0 condition [28,31] which leads to…”

“…It is also shown that this view leads to find thermal fluctuations of a Chaplygin gas model of dark energy, by knowing its mutual interaction form with dark matter, up to the desired order of thermal fluctuations [31]. Finally, we should note here that, in this approach, it is assumed that dark energy candidate satisfies the first law of thermodynamics and moreover, since the major part of cosmos is dark, non-dark sectors of cosmos are neglected from the Friedmann equations [18,[24][25][26][27][28]31]. In addition, the validity of the generalized second law of thermodynamics in a universe in which dark energy candidate interacts with radiation and dark matter is investigated in Ref.…”

“…The root of this approach comes back to the thermal fluctuation theorem [29], and indeed, thermal fluctuations theorem is valid in all area of physics such as gravitational systems [29,30]. It is also shown that this view leads to find thermal fluctuations of a Chaplygin gas model of dark energy, by knowing its mutual interaction form with dark matter, up to the desired order of thermal fluctuations [31]. Finally, we should note here that, in this approach, it is assumed that dark energy candidate satisfies the first law of thermodynamics and moreover, since the major part of cosmos is dark, non-dark sectors of cosmos are neglected from the Friedmann equations [18,[24][25][26][27][28]31].…”