Complex Scalar fields in Scalar-Tensor and Scalar-Torsion theories

TL;DR

This paper explores the cosmological dynamics of complex scalar fields within scalar-tensor and scalar-torsion theories, analyzing stationary points and their stability to understand their evolution in a flat universe.

Contribution

It introduces a detailed analysis of complex scalar fields in both theories, deriving field equations and comparing their cosmological behaviors.

Findings

Scalar-tensor and scalar-torsion theories share similar evolution features.

Stationary points and their stability are characterized.

Physical properties of solutions are discussed.

Abstract

We investigate the cosmological dynamics in a spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker geometry in scalar-tensor and scalar-torsion theories where the nonminimally coupled scalar field is a complex field. We derive the cosmological field equations and we make use of dimensionless variables in order to determine the stationary points and determine their stability properties. The physical properties of the stationary points are discussed while we find that the two-different theories, scalar-tensor and scalar-torsion theories, share many common features in terms of the evolution of the physical variables in the background space.