Abstract:Quartessence cosmological models with exponential and logarithmic equation of state are investigated using dynamical systems methods. We focus our analysis on the stability of these models.Keywords: Cosmology; Quartessence; Dynamical systems; Stability Progress in observational cosmology in the past few years suggests that the universe is dominated by two unknown components, namely, dark matter and dark energy. These two components have properties that are quite different from all the ordinary matter we know d… Show more
“…Also within extended framework at hand the Big-Bang singularity can be absent due to bouncing mechanism induced by quantum correction terms in Friedmann dynamic equations [57]. The aforementioned positive feature concerning the resolving of initial condition problem from one side and valuable phenomenology functionality of the QCMs at large scales along with this fact that they are stable into standard cosmology [58,59], from other side, motivates us to explore the response of this question: "Whether the quartessence Chaplygin cosmologies (QCCs) are still stable in a free initial singularity cosmological framework suggested by Snyder NC space approach to QG?". The result would be desirable in case of "yes".…”
Growing evidence as the observations of the CMB (cosmic microwave background), galaxy clustering and high-redshift supernovae address a stable dynamically universe dominated by the dark components. In this paper, using a qualitative theory of dynamical systems, we study the stability of a unified dark matter-dark energy framework known as quartessence Chaplygin model (QCM) with three different equation-of-states within ultraviolet (UV) deformed Friedmann-Robertson-Walker (FRW) cosmologies without Big-Bang singularity. The UV deformation is inspired by the noncommutative (NC) Snyder spacetime approach in which by keeping the transformation groups and rotational symmetry there is a dimensionless, Planck scale characteristic parameter µ0 with dual implications dependent on its sign that addresses the required invariant cutoffs for length and momentum in nature, in a separate manner. Our stability analysis is done in the (H, ρ) phase space at a finite domain concerning the hyperbolic critical points. According to our analysis, due to constraints imposed on the signs of µ0 from the phenomenological parameters involved in quartessence models (Ω * m , c 2 s , ρ * ), for an expanding and accelerating late universe, all three QCMs can be stable in the vicinity of the critical points. The requirement of stability for these quartessence models in case of admission of a minimum invariant length, can yield a flat as well as non-flat expanding and accelerating universe in which Big-Bang singularity is absent. This feedback also phenomenologically credits to braneworld-like framework versus loop quantum cosmology-like one as two possible scenarios which can be NC Snyder spacetime generators (correspond to µ0 < 0 and µ0 > 0, respectively). As a result, our analysis show that between quartessence models with Chaplygin gas equation-of-states and accelerating FRW backgrounds occupied by a minimum invariant length, there is a possibility of viability.
“…Also within extended framework at hand the Big-Bang singularity can be absent due to bouncing mechanism induced by quantum correction terms in Friedmann dynamic equations [57]. The aforementioned positive feature concerning the resolving of initial condition problem from one side and valuable phenomenology functionality of the QCMs at large scales along with this fact that they are stable into standard cosmology [58,59], from other side, motivates us to explore the response of this question: "Whether the quartessence Chaplygin cosmologies (QCCs) are still stable in a free initial singularity cosmological framework suggested by Snyder NC space approach to QG?". The result would be desirable in case of "yes".…”
Growing evidence as the observations of the CMB (cosmic microwave background), galaxy clustering and high-redshift supernovae address a stable dynamically universe dominated by the dark components. In this paper, using a qualitative theory of dynamical systems, we study the stability of a unified dark matter-dark energy framework known as quartessence Chaplygin model (QCM) with three different equation-of-states within ultraviolet (UV) deformed Friedmann-Robertson-Walker (FRW) cosmologies without Big-Bang singularity. The UV deformation is inspired by the noncommutative (NC) Snyder spacetime approach in which by keeping the transformation groups and rotational symmetry there is a dimensionless, Planck scale characteristic parameter µ0 with dual implications dependent on its sign that addresses the required invariant cutoffs for length and momentum in nature, in a separate manner. Our stability analysis is done in the (H, ρ) phase space at a finite domain concerning the hyperbolic critical points. According to our analysis, due to constraints imposed on the signs of µ0 from the phenomenological parameters involved in quartessence models (Ω * m , c 2 s , ρ * ), for an expanding and accelerating late universe, all three QCMs can be stable in the vicinity of the critical points. The requirement of stability for these quartessence models in case of admission of a minimum invariant length, can yield a flat as well as non-flat expanding and accelerating universe in which Big-Bang singularity is absent. This feedback also phenomenologically credits to braneworld-like framework versus loop quantum cosmology-like one as two possible scenarios which can be NC Snyder spacetime generators (correspond to µ0 < 0 and µ0 > 0, respectively). As a result, our analysis show that between quartessence models with Chaplygin gas equation-of-states and accelerating FRW backgrounds occupied by a minimum invariant length, there is a possibility of viability.
The present work is a phase-plane analysis of LRS Bianchi type I cosmological model with a scalar field and exponential potential. The evolution equations are reduced to an autonomous system of ordinary equations by suitable transformation of variables. We also analyse the evolution of the effective equation of state parameter for different values of curvature. The nature of critical points is analysed and stable attractors are examined from the point of view of cosmology.
One approach in modern cosmology consists in supposing that dark matter and dark energy are different manifestations of a single "quartessential" fluid. Following such idea, this work presents a study of the evolution of perturbations of density in a flat cosmological model with a modified Chaplygin gas acting as a single component. Our goal is to obtain properties of the model which can be used to distinguish it from another cosmological models which have the same solutions for the general evolution of the scale factor of the universe, without the construction of the power spectrum. Our analytical results, which alone can be used to uniquely characterize the specific model studied in our work, show that the evolution of the density contrast can be seen, at least in one particular case, as composed by a spheroidal wave function. We also present a numerical analysis which clearly indicates as one interesting feature of the model the appearance of peaks in the evolution of the density contrast.
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