Deviation from $\Lambda$CDM: Pressure Parametrization

TL;DR

This paper introduces a novel pressure-based parametrization of dark energy deviations from the cosmological constant, utilizing Taylor expansion and K-essence fields, and tests it against recent observational data.

Contribution

It proposes a new pressure parametrization approach for dark energy deviations using Taylor expansion and K-essence fields, differing from traditional equation of state methods.

Findings

Constraints on model parameters from observational data

Evidence for small deviations from the cosmological constant

Model compatibility with supernova, BAO, and galaxy cluster data

Abstract

Most parametrizations for dark energy involve the equation of state $w$ of the dark energy. In this work, we choose the pressure of the dark energy to parametrize. As $p = constant$ essentially gives a cosmological constant, we use the Taylor expansion around this behavior $p = -p_{0} + (1-a)p_{1} + ....$ to study the small deviations from the cosmological constant. In our model, the departure from the cosmological constant behavior has been modeled by the presence of extra K-essence fields while keeping the cosmological constant term untouched. The model is similar to assisted inflation scenario in a sense that for any higher order deviation in terms of Taylor series expansion, one needs multiple K-essence fields. We have also tested our model with the recent observational data coming from Supernova type Ia measurements, the baryon oscillations peak (BAO) and the gas mass fraction of the galaxy clusters inferred from X-ray observations and obtain constraints for our model parameters.