Imprints of the Metrically-coupled Dilaton on Density Perturbations in Inflationary Cosmology

TL;DR

This paper investigates how a metrically-coupled dilaton influences density perturbations during inflation, deriving constraints from cosmic microwave background observations that surpass previous experimental limits.

Contribution

It provides the first detailed calculation of density perturbation spectra in scalar-tensor theories with a metrically-coupled dilaton during inflation.

Findings

Constraints on theory parameters are an order of magnitude stronger than post-Newtonian limits.

Density perturbation spectra are affected by the dilaton's coupling.

Results inform the viability of scalar-tensor inflationary models.

Abstract

Spectra of density perturbations produced during chaotic inflation are calculated, taking both adiabatic and isocurvature modes into account in a class of scalar-tensor theories of gravity in which the dilaton is metrically coupled. Comparing the predicted spectrum of the cosmic microwave background radiation anisotropies with the one observed by the COBE-DMR we calculate constraints on the parameters of these theories, which turn out to be stronger by an order-of-magnitude than those obtained from post-Newtonian experiments.