Inflation and Large Internal Dimensions

TL;DR

This paper explores inflation in models with large internal dimensions, highlighting the necessity of bulk inflation prior to compactification to address horizon and flatness problems, especially across various unification scales.

Contribution

It analyzes the limitations of wall inflation in large internal dimension models and emphasizes the need for bulk inflation for solving cosmological issues.

Findings

Wall inflation alone is insufficient for horizon and flatness problems.

Light inflaton field requirement in low unification scale models.

Bulk inflation is necessary before compactification for a complete solution.

Abstract

We consider some aspects of inflation in models with large internal dimensions. If inflation occurs on a 3D wall after the stabilization of internal dimensions in the models with low unification scale (M ~ 1 TeV), the inflaton field must be extremely light. This problem may disappear In models with intermediate (M ~10^{11} GeV) to high (M ~ 10^{16} GeV) unification scale. However, in all of these cases the wall inflation does not provide a complete solution to the horizon and flatness problems. To solve them, there must be a stage of inflation in the bulk before the compactification of internal dimensions.