Hybrid Chaplygin Gas

Abstract

Hybrid Chaplygin gas model is put forward, in which the gases play the role of dark energy. For this model the coincidence problem is greatly alleviated. The effective equation of state of the dark energy may cross the phantom divide w = −1. Furthermore, the crossing behaviour is decoupled from any gravity theories. In the present model, w < −1 is only a transient behaviour. There is a de Sitter attractor in the future infinity. Hence, the big rip singularity, which often afflicts the models with matter whose effective equation of state less than −1, is naturally disappear. There exist stable scaling solutions, both at the early universe and the late universe. We discuss the perturbation growth of this model. We find that the index is consistent with observations.

The osgood criterion and finite‐time cosmological singularities

“…Unlike barotropic matter, the Chaplygin gas satisfies an exotic equation of state , where describes an anti‐Chaplygin gas, and describes a Chaplygin gas. Finite‐time singularities as described above have been studied a number of times in the literature in the context of Chaplygin gas universes .…”

Observational constraints on Chaplygin cosmology in a braneworld scenario with induced gravity and curvature effect

“…This model which is called GBIG-gravity, is a generalized braneworld scenario that contains both UV (ultra-violet) and IR (infra-red) limits in a unified manner: It contains stringy effect via the Gauss-Bonnet (GB) term in the bulk action as the UV sector of the theory and Induced Gravity (IG) effect which becomes important in the IR limit. The cosmological dynamics and possible realization of the phantom-like behavior in this setup are studied recently (M. Bouhmadi-Lopez & P. V. Moniz (2008Moniz ( , 2009 Yang 2009;M. H. Mohseni Sadjadi 2009).…”

“…Within the second viewpoint and focusing on the matter sector of the Einstein field equations, a well‐studied model introduces into T μν a dark energy component called the Chaplygin gas component (Amendola et al 2003; Dev, Alcaniz & Jain 2003; Bertolami et al 2004; Biesiada, Godlowski & Szydlowski 2005; Zhang, Wu & Zhang 2006; Zhang & Zhu 2006; Heydari‐Fard & Sepangi 2008; Mohseni Sadjadi 2009; Zhang, Zhu & Yang 2009). This model is similar to the DGP model in the sense that it is also characterized by a crossover length‐scale below which the gas behaves as pressureless dust and above which it approaches the behaviour of a cosmological constant.…”

ΛCDM, ΛDGP and extended phantom-like cosmologies

“…Scalar field models with their specific features provide an interesting alternative for cosmological constant and can reduce the fine tuning and coincidence problems. In this respect, several candidate models have been proposed: "quintessence" scalar field (Ratra & Peebles 1988;Saini et al 2000;Brax & Martin 2000;Barreiro et al 2000;Sahni & Wang 2000;Sahni et al 2002;Sami & Padmanabhan 2003), phantom fields (Caldwell 2002;Tsujikawa & Sami 2004;Caldwell & Linder 2005;Cai et al 2010;Moyassari & Setare 2009) and chaplygin gas (Kamenshchik et al 2001;Dev et al 2003;Amendola et al 2003;Roos 2007;Bouhmadi-López & Lazkoz 2007;Zhang et al 2006a;Zhang & Zhu 2006b;Bertolami et al 2004;Biesiada et al 2005;Heydari-Fard & Sepangi 2008;Roos 2008a,b;Zhang et al 2009;Setare 2009) are among these candidates.…”