Constraints on a scalar-tensor model with Gauss-Bonnet coupling from SN Ia and BAO observations

TL;DR

This paper investigates a scalar-tensor model with Gauss-Bonnet coupling within Horndeski theory, constrained by supernova and BAO data, revealing its cosmological viability and dynamic equation of state behaviors.

Contribution

It constrains a specific Horndeski subclass with Gauss-Bonnet coupling using observational data and reconstructs the scalar field's equation of state.

Findings

Model fits observational data well

Equation of state crosses phantom divide

Model shows cosmological viability

Abstract

In the present work, the observational consequences of a subclass of of the Horndeski theory have been investigated. In this theory a scalar field (tachyon field) non-minimally coupled to the Gauss-Bonnet invariant through an arbitrary function of the scalar field. By considering a spatially flat FRW universe, the free parameters of the model have been constrained using a joint analysis from observational data of the Type Ia supernovae and Baryon Acoustic Oscillations measurements. The best fit values obtained from these datasets are then used to reconstruct the equation of state parameter of the scalar field. The results show the phantom, quintessence and phantom divide line crossing behavior of the equation of state and also cosmological viability of the model.