On Isotropic Turbulence in the Dark Fluid Universe

TL;DR

This paper investigates how isotropic turbulence in dark fluid cosmology affects the universe's evolution, showing that turbulence influences late-time behavior and can prevent future singularities like the Big Rip.

Contribution

It introduces a perturbative approach to incorporate isotropic turbulence into FRW cosmology and demonstrates its potential to alter the universe's ultimate fate.

Findings

Turbulence effects fade in Hubble parameter and energy density at late times.

Turbulence causes a logarithmic divergence in the scale factor.

Turbulence can prevent the Big Rip, leading to a de Sitter universe.

Abstract

As first part of this work, experimental information about the decay of isotropic turbulence in ordinary hydrodynamics, u^2(t) proportional to t^{-6/5}, is used as input in FRW equations in order to investigate how an initial fraction f of turbulent kinetic energy in the cosmic fluid influences the cosmological development in the late, quintessence/phantom, universe. First order perturbative theory to the first order in f is employed. It turns out that both in the Hubble factor, and in the energy density, the influence from the turbulence fades away at late times. The divergences in these quantities near the Big Rip behave essentially as in a non-turbulent fluid. However, for the scale factor, the turbulence modification turns out to diverge logarithmically. As second part of our work, we consider the full FRW equation in which the turbulent part of the dark energy is accounted for by a separate term. It is demonstrated that turbulence occurrence may change the future universe evolution due to dissipation of dark energy. For instance, phantom-dominated universe becomes asymptotically a de Sitter one in the future, thus avoiding the Big Rip singularity.