Scalar Field as Dark Matter and Machian Cosmological Solution in the Generalized Scalar-Tensor Theory of Gravitation

TL;DR

This paper explores a generalized scalar-tensor theory of gravitation where a scalar field acts as dark matter, and discusses a Machian cosmological solution with a varying cosmological constant, highlighting the evolution of the universe's matter content.

Contribution

It introduces a scalar field with an exponential potential as dark matter within a generalized scalar-tensor framework and analyzes its cosmological implications.

Findings

Scalar field acts as dark matter with exponential potential

The equation of state coefficient approaches -1/3 during expansion

The coupling function diverges to negative infinity as universe expands

Abstract

The Machian cosmological solution satisfying $\phi =O(\rho /\omega)$ in the generalized scalar-tensor theory of gravitation with the varying cosmological constant is summarized. The scalar field $\phi $ with the exponential potential is introduced as dark matter and the barotropic evolution of matter in the universe is discussed. As the universe expands, the coefficient $\gamma $ of the equation of state approaches to -1/3 and the coupling function $\omega (\phi)$ diverges to $-\infty $.