Some Aspects of Brane Inflation

TL;DR

This paper explores brane inflation, highlighting how higher-dimensional theories motivate the inflaton potential and examining how brane interactions can influence density perturbations and observable cosmological signatures.

Contribution

It emphasizes the motivation of inflaton potentials from higher-dimensional theories and analyzes the effects of velocity-dependent brane potentials on density perturbations.

Findings

Velocity-dependent potentials can significantly affect density perturbation spectra.

Brane inflation models can produce observable tensor-to-scalar ratios.

Higher-dimensional motivations provide natural inflaton potentials.

Abstract

The inflaton potential in four-dimensional theory is rather arbitrary, and fine-tuning is required generically. By contrast, inflation in the brane world scenario has the interesting feature that the inflaton potential is motivated from higher dimensional gravity, or more generally, from bulk modes or string theory. We emphasize this feature with examples. We also consider the impact on the spectrum of density perturbation from a velocity-dependent potential between branes in the brane inflationary scenario. It is likely that such a potential can have an observable effect on the ratio of tensor to scalar perturbations.