Cosmic acceleration without dark energy: background tests and thermodynamic analysis

Abstract

A new cosmic scenario with gravitationally induced particle creation is proposed. In this model the Universe evolves from an early to a late time de Sitter era, with the recent accelerating phase driven only by the negative creation pressure associated with the cold dark matter component. The model can be interpreted as an attempt to reduce the so-called cosmic sector (dark matter plus dark energy) and relate the two cosmic accelerating phases (early and late time de Sitter expansions). A detailed thermodynamic analysis including possible quantum corrections is also carried out. For a very wide range of the free parameters, it is found that the model presents the expected behavior of an ordinary macroscopic system in the sense that it approaches thermodynamic equilibrium in the long run (i.e., as it nears the second de Sitter phase). Moreover, an upper bound is found for the Gibbons-Hawking temperature of the primordial de Sitter phase. Finally, when confronted with the recent observational data, the current 'quasi'-de Sitter era, as predicted by the model, is seen to pass very comfortably the cosmic background tests.PACS numbers: 98.80.-k, 95.35.+d, 95.36.+x

Gravitationally induced particle production: Thermodynamics and kinetic theory

“…More recently, even a complete cosmology where the space-time-matter evolves between an early and a late time de Sitter phases driven by particle production has been proposed and its predictions compared with the available astronomical data [14]. The consistence of such a scenario with the generalized second law of thermodynamics was also discussed in detail by Mimoso and Pavón [15] (see also [18] for a more general analysis).…”

“…In the last few years, much attention has been paid for cosmologies driven by gravitational "adiabatic" particle production where matter and entropy are generated but the specific entropy (per particle) remains constant [10][11][12][13][14][15][16][17][18]. Since the creation process is macroscopically described by a negative pressure of quantum origin (back reaction), these models have been investigated as a possi-bility to unify the so-called cosmological dark sector.…”

CCDM model with spatial curvature and the breaking of ``dark degeneracy''

“…It has already been studied a linear dependence with the Hubble parameter [15], and at the time of writing this paper, it has been proposed a power law dependence on Hubble parameter [16]. It is clear to us that the expansion acceleration is a recent feature, so the CDM creation also must be recent.…”

“…We have found χ 2 min = 16.344, α = 0.775 +0.059+0.098 −0.064−0.11 +0.14 −0. 16 and Ω k = −0.041 ± 0.069 ± 0.11 ± 0.16. In order to improve these constraints, we made a combined analysis with SN Ia data.…”

Interacting cosmic fluids and phase transitions under a holographic modeling for dark energy

“…Perhaps an interaction between dynamical vacuum energy and matter is also possible [5] or a scenario where a particle creation mechanism which can lead to cosmic acceleration [6]. It appears unnatural to think that cosmic fluids coexist and do not interact with each other as is usual in the standard CDM model (both components evolve independently and satisfy the usual energy conservation equations).…”