Evolution of shifted cosmological parameter and shifted dust matter in a two-phase tachyonic field universe

TL;DR

This paper models the evolution of a tachyonic scalar field in two phases, introducing shifted cosmological parameters and matter, and constrains their interaction using observational data to understand universe expansion and structure formation.

Contribution

It presents a novel two-phase tachyonic field model with shifted parameters and constrains interaction strength using observational data, exploring implications for universe evolution.

Findings

Interaction strength constrained by observational data.

Model explains evolution of shifted parameters over redshift.

Implications for universe age and structure formation.

Abstract

We propose a model of the evolution of the tachyonic scalar field over two phases in the universe. The field components do not interact in phase I, while in the subsequent phase II, they change flavours due to relative suppression of the radiation contribution. In phase II, we allow them to interact mutually with time-independent perturbation in their equations of state, as Shifted Cosmological Parameter (SCP) and Shifted Dust Matter (SDM). We determine the solutions of their scaling with the cosmic redshift in both phases. We further suggest the normalized Hubble function diagnostic, which, together with the low- and high-redshift $H(z)$ data and the concordance values of the present density parameters from the CMBR, BAO statistics etc., constrains the strength of interaction, by imposing the viable conditions to break degeneracy in 3-parameter $(\gamma, \varepsilon, \dot{\phi}^2)$ space. The range of redshifts $(z=0.1$ to $z=1.75)$ is chosen to highlight the role of interaction during structure formation, and it may lead to a future analysis of power spectrum in this model \emph{vis a vis} Warm Dark Matter (WDM) or $\Lambda$CDM models. We further calculate the influence of interaction in determining the age of the universe at the present epoch, within the degeneracy space of model parameters.