Relic Gravity Waves from Braneworld Inflation

TL;DR

This paper explores how extra-dimensional effects in braneworld inflation influence relic gravity wave spectra, predicting a blue tilt that could be detectable by future gravitational wave observatories.

Contribution

It introduces a model where steep potentials enable a scalar field to drive inflation and dark energy, affecting the relic gravity wave spectrum with a characteristic blue tilt.

Findings

Relic gravity wave spectrum exhibits a blue tilt at short wavelengths.

Kinetic regime prior to radiation domination impacts gravity wave characteristics.

Detection prospects for gravity waves are discussed in the context of LIGO II and LISA.

Abstract

We discuss a scenario in which extra dimensional effects allow a scalar field with a steep potential to play the dual role of the inflaton as well as dark energy (quintessence). The post-inflationary evolution of the universe in this scenario is generically characterised by a `kinetic regime' during which the kinetic energy of the scalar field greatly exceeds its potential energy resulting in a `stiff' equation of state for scalar field matter $P_\phi \simeq \rho_\phi$. The kinetic regime precedes the radiation dominated epoch and introduces an important new feature into the spectrum of relic gravity waves created quantum mechanically during inflation. The gravity wave spectrum increases with wavenumber for wavelengths shorter than the comoving horizon scale at the commencement of the radiative regime. This `blue tilt' is a generic feature of models with steep potentials and imposes strong constraints on a class of inflationary braneworld models. Prospects for detection of the gravity wave background by terrestrial and space-borne gravity wave observatories such as LIGO II and LISA are discussed.