Stability properties of some perfect fluid cosmological models

Gorini, Vittorio; Kamenshchik, Alexander Yu.; Moschella, Ugo; Pasquier, Vincent; Starobinsky, Alexei A.

doi:10.1103/physrevd.72.103518

Cited by 92 publications

(89 citation statements)

References 58 publications

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“…Assuming that the kinetic term is of Born-Infeld type, as in Refs. [43,44,47,48,49], 15) with M a suitable mass-scale, which implies ρ = f (ϕ)/ 1 − 2X/M 4 , we get…”

Section: A Lagrangians Of the Typementioning

confidence: 99%

“…If one requires the exact condition that our unified DM fluid has a constant pressure term p = −Λ and looks for a scalar field model with canonical kinetic term, one arrives at an exact solution with potential V (φ) = (Λ/2)[cosh 2 ( √ 3φ/2) + 1] (see also Ref. [43,44]). Using standard criteria (e.g.…”

Section: Unified Dark Matter From a Scalar Field With Non-canonicmentioning

confidence: 99%

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Unified Dark Matter in Scalar Field Cosmologies

2007

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Considering the general Lagrangian of k-essence models, we study and classify them through variables connected to the fluid equation of state parameter wκ. This allows to find solutions around which the scalar field describes a mixture of dark matter and cosmological constant-like dark energy, an example being the purely kinetic model proposed by Scherrer. Making the stronger assumption that the scalar field Lagrangian is exactly constant along solutions of the equation of motion, we find a general class of k-essence models whose classical trajectories directly describe a unified dark matter/dark energy (cosmological constant) fluid. While the simplest case of a scalar field with canonical kinetic term unavoidably leads to an effective sound speed cs = 1, thereby inhibiting the growth of matter inhomogeneities, more general non-canonical k-essence models allow for the possibility that cs ≪ 1 whenever matter dominates.

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“…Assuming that the kinetic term is of Born-Infeld type, as in Refs. [43,44,47,48,49], 15) with M a suitable mass-scale, which implies ρ = f (ϕ)/ 1 − 2X/M 4 , we get…”

Section: A Lagrangians Of the Typementioning

confidence: 99%

Section: Unified Dark Matter From a Scalar Field With Non-canonicmentioning

confidence: 99%

Unified Dark Matter in Scalar Field Cosmologies

2007

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“…This issue has already been investigated for some DE models. It was shown that chaplygin gas and tachyon DE have positive squared speeds of sound with, v 2 s = −w, and thus they are supposed to be stable against small perturbations [29,30]. However, the perfect fluid of holographic DE with future event horizon is classically unstable because its squared speed is always negative [31] .…”

Section: Introductionmentioning

confidence: 99%

Instability of QCD Ghost Dark Energy Model

Ebrahimi

Sheykhi

2011

Int. J. Mod. Phys. D

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We investigate the instability of the ghost dark energy model against perturbations in different cases. To this goal we use the squared sound speed v 2 s whose sign determines the stability of the model. When v 2 s < 0 the model is unstable against perturbation. At first we discuss the noninteracting ghost dark energy model in a flat FRW universe and find out that such a model is unstable due to the negativity of the v 2 s in all epoches. The interacting ghost dark energy model in both flat and non-flat universe are studied in the next parts and in both cases we find that the squared sound speed of ghost dark energy is always negative. This implies that the perfect fluid for ghost dark energy is classically unstable against perturbations. In both flat and non flat cases we find that the instability of the model increases with increasing the value of the interacting coupling parameter.

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“…In particular, for the background solutions these two ways to describe dark energy models are equivalent. However, one cannot assume univocally this equivalence, for example in the stability of the solutions [31] or in the studies of cosmological perturbations [13,32].…”

Section: Introductionmentioning

confidence: 99%

The generalized second law of thermodynamics for interacting f(R) gravity

Herrera

Videla

2014

Int. J. Mod. Phys. D

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We examine the validity of the generalized second law (GSL) of gravitational thermodynamics in the context of interacting f (R) gravity. We take into account that the boundary of the universe to be confined by the dynamical apparent horizon in a flat FRW universe. We study the effective equation of state, deceleration parameter and GSL in this interaction-framework. We find that the evolution of the total entropy increases through the interaction term. As a example, we consider a f (R) gravity with a power-law dependence on the curvature R. Here, we find exact solutions for a model in which the interaction term is related to the total energy density of matter.

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Stability properties of some perfect fluid cosmological models

Cited by 92 publications

References 58 publications

Unified Dark Matter in Scalar Field Cosmologies

Unified Dark Matter in Scalar Field Cosmologies

Instability of QCD Ghost Dark Energy Model

The generalized second law of thermodynamics for interacting f(R) gravity

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