Gravitational Wave Constraints on Multi-Brane Inflation

TL;DR

This paper explores multi-brane inflation models, showing they can produce detectable gravitational waves and non-Gaussianity, relaxing constraints from single-brane scenarios and offering testable predictions for future experiments.

Contribution

It introduces a new class of multi-brane inflation models with an effective action derived via an SU(2) iterative technique, expanding the landscape of inflationary scenarios.

Findings

Multi-brane models can generate observable gravitational waves.

These models can produce significant non-Gaussianity.

Constraints on tensor-scalar ratio are relaxed in multi-brane setups.

Abstract

A class of non-canonical inflationary models is identified, where the leading-order contribution to the non-Gaussianity of the curvature perturbation is determined by the sound speed of the fluctuations in the inflaton field. Included in this class of models is the effective action for multiple coincident branes in the finite n limit. The action for this configuration is determined using a powerful iterative technique, based upon the fundamental representation of SU(2). In principle the upper bounds on the tensor-scalar ratio that arise in the standard, single-brane DBI inflationary scenario can be relaxed in such multi-brane configurations if a large and detectable non-Gaussianity is generated. Moreover models with a small number of coincident branes could generate a gravitational wave background that will be observable to future experiments.