Inflationary phase in Generalized Brans-Dicke theory

TL;DR

This paper presents a solution for exponential inflation within a generalized Brans-Dicke model featuring a variable coupling, showing that cosmic acceleration can occur even with negative lambda.

Contribution

It introduces an exponential inflation solution in a generalized Brans-Dicke theory with a variable coupling constant, extending inflationary models beyond standard General Relativity.

Findings

Cosmic acceleration occurs with negative lambda.

Pressure is proportional to density, with a proportionality constant less than -2/3.

Inflationary solution differs from standard GR by variable coupling and altered equation of state.

Abstract

We find a solution for exponential inflation in a Brans-Dicke generalized model, where the coupling "constant " is variable. While in General Relativity the equation of state is p is equal to minus rho, here we find p proportional to rho, where the proportionality constant is smaller than -2/3. The negativity of cosmic pressure implies acceleration of the expansion, even with lambda < 0 >.