Matter with dilaton charge in Weyl-Cartan spacetime and evolution of the Universe

TL;DR

This paper develops a theoretical model of a dilaton-spin fluid in Weyl-Cartan spacetime, exploring its implications for cosmology, including the universe's evolution, avoiding initial singularity, and explaining accelerated expansion.

Contribution

It introduces a variational formalism for dilaton-spin fluid in Weyl-Cartan spacetime and derives modified cosmological equations with novel insights into universe evolution.

Findings

Absence of initial cosmological singularity.

Existence of two inflection points in the scale factor.

Inflation-like solution for early universe expansion.

Abstract

The perfect dilaton-spin fluid (as a model of the dilaton matter, the particles of which are endowed with intrinsic spin and dilaton charge) is considered as the source of the gravitational field in a Weyl-Cartan spacetime. The variational theory of such fluid is constructed and the dilaton-spin fluid energy-momentum tensor is obtained. The variational formalism of the gravitational field in a Weyl-Cartan spacetime ia developed in the exterior form language. The homogeneous and isotropic Universe filled with the dilaton matter as the dark matter is considered and one of the field equations is represented as Einstein-like equation which leads to the modified Friedmann-Lemaitre equation. From this equation the absence of the initial singularity in the cosmological solution follows. Also the existence of two points of inflection of the scale factor function is established, the first of which corresponds to the early stage of the Universe and the second one corresponds to the modern era when the expansion with deceleration is replaced by the expansion with acceleration. The possible equations of state for the self-interacting cold dark matter are found on the basis of the modern observational data. The inflation-like solution is obtained.