Bianchi type-I universe models with nonlinear viscosity

Abstract

In this paper we study the evolution of spatially homogeneous and anisotropic Bianchi type-I Universe models with the cosmological constant, Λ, and filled with nonlinear viscous fluid. The dynamical equations for these models are obtained and solved for some special cases. We calculate the statefinder parameters for the models and display them in the s-r-plane.

The Hubble IR cutoff in holographic ellipsoidal cosmologies

“…In conclusion, the only relevant non-vacuum solution with anisotropic pressure is described by the metric (19) and the stiff holographic energy (17). The condition a(t) = b(t) α is fundamental to obtaining this result.…”

“…A detailed analysis of the dynamical systems corresponding to a Bianchi type-I anisotropic universe filled with a cosmological constant and a fluid with bulk viscosity was realized in [14]. Anisotropic universes of this type filled with perfect fluid matter with or without dissipative process and a cosmological constant has been investigated in [15][16][17][18][19][20]. A variable cosmological constant has also been taken into consideration in related research.…”

Phase space analysis of a FRW cosmology in the Maxwell–Cattaneo approach

“…We have introduced the definition A = 4ξ 2 0 + 1 Table 2 Eigenvalues and some basic physical parameters for the critical points listed in Table 1, see also Eqs. (20) and (21). We have introduced the definition B = γ de γ de −4ξ 0 (γ de − 1) (γ de − 2) 2 + 5γ 2 de − 20γ de + 28 − 16 + 4…”

“…Another interesting way to recover accelerated solutions consistent with the latest observations, is by considering a more realistic description of the fluids. This task is carry out by considering imperfect fluids having bulk viscosity [12,13,14,15,16,17,18,19,20,21,22,23,24,25] 2 . The presence of this dissipative mechanism is allowed by the commonly accepted spatial isotropic paradigm of the Universe [7].…”

“…where the bulk viscosity coefficient is written as a function of the Hubble paramater [51,52,53,37,20,54,55,56], via de Friedmann equations. In the framework of the Eckart theory, this latter ansatz was studied in [37] to describe the physical viability of a cosmological model in which the dark energy fluid interact with a viscous dark matter.…”