Recombination of Intersecting D-Branes and Cosmological Inflation

TL;DR

The paper demonstrates that non-supersymmetric configurations of intersecting D-branes at angles in type II string theory can realize slow-roll inflation with the interbrane distance $Y$ acting as the inflaton. By focusing on a compact $\mathbb{R}^{3,1}\times T^6$ setup and allowing two intersection angles, the authors derive an attractive potential and show that inflation can proceed with modest tuning of volumes and angles; inflation ends via tachyonic brane recombination, and in many cases the final state can again feature two branes at angles, enabling post-inflation chiral brane models. They treat two explicit realizations with D5- and D6-branes, derive slow-roll parameters, COBE normalization, and spectral indices, and provide plausible numerical examples with $M_s\sim10^{13}$ GeV. The work highlights the potential for embedding inflation in intersecting brane models while preserving useful features for particle physics model building after inflation, and it identifies important directions for moduli stabilization and reheating studies. Overall, this approach offers a stringy, geometrically rich realization of hybrid-like inflation with a natural mechanism for ending inflation and a realistic pathway to post-inflation phenomenology.

Abstract

We consider the interactions between Dp-branes intersecting at an arbitrary number of angles in the context of type II string theory. For cosmology purposes we concentrate in the theory on R^{3,1} x T^6. Interpreting the distance between the branes as the inflaton field, the branes can intersect at most at two angles on the compact space. If the configuration is non-supersymmetric we will have an interbrane potential that provides an effective cosmological inflationary epoch at the four dimensional intersection between the branes. The end of inflation occurs when the interbrane distance becomes small compared with the string scale, where a tachyon develops triggering the recombination of the branes. We study this recombination due to tachyon instabilities and we find the possibility for the final configuration to be again branes intersecting at two angles. This preserves the interesting features that are present in the intersecting brane models from the string model building point of view also after the end of inflation. This fact was not present in the models of branes intersecting at just one angle. This kind of recombination can be also important in other string contexts.