Cosmological models with linearly varying deceleration parameter

TL;DR

This paper introduces a new linearly varying deceleration parameter model that generalizes previous constant models, fits observational data better, and predicts a universe ending in a big-rip with quintom-like behavior.

Contribution

It proposes a novel linearly varying deceleration parameter law that extends existing models and aligns more closely with observational data.

Findings

Only spatially closed and flat universes are allowed.

The cosmological fluid exhibits quintom-like behavior.

The universe ends with a big-rip.

Abstract

We propose a new law for the deceleration parameter that varies linearly with time and covers Berman's law where it is constant. Our law not only allows one to generalize many exact solutions that were obtained assuming constant deceleration parameter, but also gives a better fit with data (from SNIa, BAO and CMB), particularly concerning the late time behavior of the universe. According to our law only the spatially closed and flat universes are allowed; in both cases the cosmological fluid we obtain exhibits quintom like behavior and the universe ends with a big-rip. This is a result consistent with recent cosmological observations.