Massless and massive graviton spectra in anisotropic dilatonic braneworld cosmologies

TL;DR

This paper investigates the spectra of massless and massive gravitons in an anisotropic dilatonic braneworld cosmology, revealing how the dilaton influences mode dominance and spectral amplitudes during universe evolution.

Contribution

It provides a detailed analysis of graviton spectra in an anisotropic dilatonic braneworld, highlighting the impact of the dilaton on mode enhancement and suppression.

Findings

Massless spectrum matches standard four-dimensional models.

High-energy massive modes can be strongly enhanced.

Dilaton reduces the relative importance of massive modes.

Abstract

We consider a braneworld model in which an anisotropic brane is embedded in a dilatonic background. We solve the background solutions and study the behavior of the perturbations when the universe evolves from an inflationary Kasner phase to a Minkowski phase. We calculate the massless mode spectrum, and find that it does not differ from what expected in standard four-dimensional cosmological models. We then evaluate the spectrum of both light (ultrarelativistic) and heavy (nonrelativistic) massive modes, and find that, at high energies, there can be a strong enhancement of the Kaluza-Klein spectral amplitude, which can become dominant in the total spectrum. The presence of the dilaton, on the contrary, decrease the relative importance of the massive modes.