Inflation on the Brane with Vanishing Gravity

TL;DR

This paper proposes a novel brane inflation model using a 2D spherical compactification where antipodal projection removes problematic gravitational forces, enabling sustained inflation.

Contribution

It introduces a new unwarped, non-supersymmetric setup with antipodal projection on a sphere to eliminate gravitational contributions to the inflationary potential.

Findings

Gravitational potential between branes is dominated by KK modes and radion exchange.

Antipodal projection on the sphere removes level-1 KK modes, nullifying gravitational effects.

The model stabilizes the sphere's size using cosmological constant and magnetic flux.

Abstract

Many existing models of brane inflation suffer from a steep irreducible gravitational potential between the branes that causes inflation to end too early. Inspired by the fact that point masses in 2+1 D exert no gravitational force, we propose a novel unwarped and non-supersymmetric setup for inflation, consisting of 3-branes in two extra dimensions compactified on a sphere. The size of the sphere is stabilized by a combination of a bulk cosmological constant and a magnetic flux. Computing the 4D effective potential between probe branes in this background, we find a non-zero contribution only from exchange of level-1 KK modes of the graviton and radion. Identifying antipodal points on the 2-sphere projects out these modes, eliminating entirely the troublesome gravitational contribution to the inflationary potential.