Born-Again Braneworld

TL;DR

This paper introduces a novel cosmological braneworld model where branes collide and reborn with opposite tensions, featuring unique radion dynamics that blend inflationary and pre-big-bang characteristics, affecting gravitational wave spectra.

Contribution

It presents a new rebirth scenario for branes with opposite tensions, incorporating scalar-tensor gravity and radion dynamics, bridging inflation and pre-big-bang models.

Findings

Radion-driven dynamics differ from standard inflation.

Gravitational waves may have a very blue spectrum.

Inflaton produces a scale-invariant spectrum.

Abstract

We propose a cosmological braneworld scenario in which two branes collide and emerge as reborn branes whose tensions have signs opposite to the original tensions of the respective branes. In this scenario, gravity on each of the branes is described by a scalar-tensor-type theory in which the radion plays the role of the gravitational scalar, and the branes are assumed to be inflating. However, the whole dynamics is different from those of the usual inflation, due to the non-trivial dynamics of the radion field. Transforming the conformal frame to the Einstein frame, this born-again scenario resembles the pre-big-bang scenario. Thus, our scenario has features of both inflation and pre-big-bang scenarios. In particular, gravitational waves produced from vacuum fluctuations may have a very blue spectrum, while the inflaton field gives rise to a standard scale-invariant spectrum.