The new form of the equation of state for dark energy fluid and accelerating universe

TL;DR

This paper introduces a generalized inhomogeneous equation of state for dark energy, incorporating pressure derivatives and relaxation dynamics, leading to models of accelerating universes that can transition from deceleration to acceleration.

Contribution

It proposes a novel generalized inhomogeneous EoS for dark energy, including pressure derivatives and relaxation equations, extending previous models and enabling new cosmological solutions.

Findings

Constructed accelerating FRW cosmologies with de Sitter or oscillating behavior.

Demonstrated transition from deceleration to acceleration in the models.

Showed consistency of dark energy-matter coupling with the generalized EoS.

Abstract

We suggest to generalize the dark energy equation of state (EoS) by introduction the relaxation equation for pressure which is equivalent to consideration of the inhomogeneous EoS cosmic fluid which often appears as the effective model from strings/brane-worlds. As another, more wide generalization we discuss the inhomogeneous EoS which contains derivatives of pressure. For several explicit examples motivated by the analogy with classical mechanics the accelerating FRW cosmology is constructed. It turns out to be the asymptotically de Sitter or oscillating universe with possible transition from deceleration to acceleration phase. The coupling of dark energy with matter in accelerating FRW universe is considered, it is shown to be consistent with constrained (or inhomogeneous) EoS.