The Scalar-Tensor Inflationary Cosmology

Abstract

In this paper the scalar-tensor theory of gravity is assumed to describe the evolution of the universe and the gravitational scalar $ϕ$ is ascribed to play the role of inflaton. The theory is characterized by the specified coupling function $ω(ϕ)$ and the cosmological function $λ(ϕ)$. The function $λ(ϕ)$ is nearly constant for $0<ϕ<0.1$ and $λ(1)=0$. The functions $λ(ϕ)$ and $ω(ϕ)$ provide a double-well potential for the motion of $ϕ(t)$. Inflation commences and ends naturally by the dynamics of the scalar field. The energy density of matter increases steadily during inflation. When the constant $Γ$ 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.