De Sitter ground state of scalar-tensor gravity and its primordial perturbation

TL;DR

This paper reconstructs an exact de Sitter solution in scalar-tensor gravity, showing it produces non-scale-invariant primordial perturbations and predicts suppressed tensor modes, with implications for early universe inflation.

Contribution

It is the first to demonstrate that exact de Sitter in scalar-tensor gravity yields non-scale-invariant perturbations and explores tensor mode suppression.

Findings

Exact de Sitter solution reconstructed in scalar-tensor gravity.

Primordial perturbations are non-scale-invariant.

Tensor modes are strongly suppressed in conformal coupling case.

Abstract

Scalar-tensor gravity is one of the most competitive gravity theory to Einstein's relativity. We reconstruct the exact de Sitter solution in scalar-tensor gravity, in which the non-minimal coupling scalar is rolling along the potential. This solution may have some relation to the early inflation and present acceleration of the universe. We investigated its primordial quantum perturbation around the adiabatic vacuum. We put forward for the first time that exact de Sitter generates non-exactly scale invariant perturbations. In the conformal coupling case, this model predicts that the tensor mode of the perturbation (gravity wave) is strongly depressed.