Inflation in models with large extra dimension driven by a bulk scalar field

Abstract

We discuss inflation in models with large extra dimensions, driven by a bulk scalar field. The brane inflaton is then a single effective field, obtained from the bulk scalar field by scaling. The self-interaction terms of the effective brane inflaton are then naturally suppressed. The picture is consistent with a fundamental string scale in the TeV range without the problem of a superlight inflaton. If hybrid inflation is considered, the right prediction for the density perturbations as observed by the Cosmic Background Explorer can be obtained without any fine-tuning. The bulk inflaton then decays preferentially into brane Higgs fields and reheating follows.

Inflation on a single brane: Exact solutions

“…Various cosmological aspects of branes embedded in five dimensions have been investigated [4][5][6][7][8][9][10][11][12][13][14][15]. The effects of including a scalar field in the bulk have also been studied [13][14][15].…”

“…The effects of including a scalar field in the bulk have also been studied [13][14][15]. In this paper, we consider a co-dimension 1 brane with positive tension, λ, embedded in vacuum Einstein gravity with a negative cosmological constant.…”

A dynamical stabilization of the radion potential

“…In our case, for two large extra dimensions the last 43 e-foldings are supported by adiabatic perturbations due to the slow roll of χ 2 field [8].…”

“…Since, the actual mass of the radion is very small, for instance, for two large extra dimensions it is ∼ O(10 −2 ) eV, we can not expect the radion field to reheat the Universe to the extent that we obtain from a bulk scalar field/fields. On the other hand, we require the bulk scalar fields in order to produce density perturbations during inflation [8]. Following this wisdom, we invoke scalar fields χ i , living in the bulk along with gravity.…”

“…Since, for our purpose, the masses of the fields have a natural cut-off scale ∼ M * , it is extremely difficult to produce adequate density perturbation for a simple chaotic inflationary scenario [6,7]. For this reason hybrid model has been chosen because it may overcome a low level of density perturbation [8]. In this section we briefly review the model.…”