From de Sitter to de Sitter: A Thermal Approach to Running Vacuum Cosmology and the Non-Canonical Scalar Field Description

TL;DR

This paper presents a thermal approach to describe the evolution of the universe between two de Sitter phases, deriving a running vacuum model from thermodynamics and linking it to a non-canonical scalar field, offering new insights into cosmological puzzles.

Contribution

It introduces an analytical expression for running vacuum based on thermodynamics and demonstrates its equivalence to a non-canonical scalar field model, providing a novel perspective on cosmic evolution.

Findings

Derived a thermal-based analytical expression for running vacuum.

Established a correspondence between the thermal vacuum model and a scalar field description.

Proposed a non-singular cosmological scenario connecting two de Sitter states.

Abstract

The entire classical cosmological history between two extreme de Sitter vacuum solutions is discussed based on Einstein's equations and non-equilibrium thermodynamics. The initial non-singular de Sitter state is characterised by a very high energy scale which is equal or smaller than the reduced Planck mass. It is structurally unstable and all the continuous created matter, energy and entropy of the material component comes from the irreversible flow powered by the primeval vacuum energy density. The analytical expression describing the running vacuum is obtained from the thermal approach. It opens a new perspective to solve the old puzzles and current observational challenges plaguing the cosmic concordance model driven by a rigid vacuum. Such a scenario is also modelled through a non-canonical scalar field. It is demonstrated that the resulting scalar field model is shown to be step by step a faithful analytical representation of the thermal running vacuum cosmology.