Chaplygin Gas of Tachyon Nature Imposed by Symmetry and Constrained via H(z) Data

TL;DR

This paper develops a cosmological model with a tachyon field interpreted as Chaplygin gas, constrained by symmetry principles, and tests its consistency with observational H(z) data, showing the tachyon must be dynamical.

Contribution

It derives a minimally coupled, constant potential Chaplygin gas model from symmetry constraints and compares its dynamics with observational data.

Findings

The model favors minimal coupling and constant potential.

Observational data suggest the tachyon field is dynamical.

The symmetry approach constrains the form of the dark energy component.

Abstract

An action of general form is proposed for a Universe containing matter, radiation and dark energy. The latter is interpreted as a tachyon field non-minimally coupled to the scalar curvature. The Palatini approach is used when varying the action so the connection is given by a more generic form. Both the self-interaction potential and the non-minimally coupling function are obtained by constraining the system to present invariability under global point transformation of the fields (Noether Symmetry). The only possible solution is shown to be that of minimal coupling and constant potential (Chaplygin gas). The behavior of the dynamical properties of the system is compared to recent observational data, which infers that the tachyon field must indeed be dynamical.