Dilaton Contributions to the Cosmic Gravitational Wave Background

TL;DR

This paper investigates how a dilaton field in higher-dimensional Brans-Dicke cosmology influences the generation and spectrum of primordial gravitational waves, linking early universe dynamics to current observational constraints.

Contribution

It introduces a detailed analysis of dilaton effects on gravitational wave production in higher-dimensional models, highlighting their impact on the observable graviton spectrum.

Findings

Dilaton evolution significantly alters the gravitational wave spectrum.

Current observational bounds constrain early universe dilaton dynamics.

Spectral energy density of gravitons is sensitive to higher-dimensional effects.

Abstract

We consider the cosmological amplification of a metric perturbation propagating in a higher-dimensional Brans-Dicke background, including a non trivial dilaton evolution. We discuss the properties of the spectral energy density of the produced gravitons (as well as of the associated squeezing parameter), and we show that the present observational bounds on the graviton spectrum provide significant information on the dynamical evolution of the early universe.