The Scalar-Tensor Inflationary Cosmology

TL;DR

This paper explores a scalar-tensor gravity model where the scalar field acts as the inflaton, naturally driving inflation and potentially explaining cold dark matter without reheating, with specific functions shaping the inflationary dynamics.

Contribution

It introduces a scalar-tensor inflationary model with specific coupling and cosmological functions that naturally end inflation and unify inflaton and dark matter roles.

Findings

Inflation ends naturally via scalar field dynamics.

End-of-inflation temperature around 10^{14} GeV without reheating.

Scalar field potentially accounts for cold dark matter.

Abstract

In this paper the scalar-tensor theory of gravity is assumed to describe the evolution of the universe and the gravitational scalar $\phi$ is ascribed to play the role of inflaton. The theory is characterized by the specified coupling function $\omega(\phi)$ and the cosmological function $\lambda(\phi)$. The function $\lambda(\phi)$ is nearly constant for $0<\phi<0.1$ and $\lambda(1)=0$. The functions $\lambda(\phi)$ and $\omega(\phi)$ provide a double-well potential for the motion of $\phi(t)$. Inflation commences and ends naturally by the dynamics of the scalar field. The energy density of matter increases steadily during inflation. When the constant $\Gamma$ in the action is determined by the present matter density, the temperature at the end of inflation is of the order of $10^{14} GeV$ in no need of reheating. Furthermore, the gravitational scalar is just the cold dark matter that men seek for.