Cosmological models with dynamical lambda in scalar-tensor theories

TL;DR

This paper explores scalar-tensor cosmological models with a dynamic cosmological constant, deriving exact solutions and comparing key parameters with observations to understand universe evolution.

Contribution

It introduces new exact solutions in scalar-tensor theories with a dynamical lambda and analyzes their observational viability.

Findings

Some models avoid initial singularities

Derived cosmological parameters match observational data

Solutions exhibit exponential or power-law expansion

Abstract

In the context of a family os scalar-tensor theories with a dynamical $\Lambda$, that is a binomial on the scalar field, the cosmological equations are considered. A general barotropic state equation $p=(\gamma-1)\rho$, for a perfect fluid is used for the matter content of the Universe. Some Friedmann- Robertson-Walker exact solutions are found, they have scale factor wich shows exponential or power law dependence on time. For some models the singularity can be avoided. Cosmological parameters as $\Omega_m$, $\Omega_{\Lambda}$, $q_0$ and $t_0$ are obtained and compared with observational data.