Scalar fluctuations of the scalar metric during inflation from a non-perturbative 5D large-scale repulsive gravity model

TL;DR

This paper develops a non-perturbative 5D gravity model to analyze scalar metric fluctuations during inflation, showing how these fluctuations become scale-invariant on large cosmological scales.

Contribution

It introduces a novel non-perturbative formalism for scalar fluctuations in a 5D extended gravity model, applicable during inflation.

Findings

Fluctuation spectrum becomes scale-invariant during inflation

Effective 4D Schwarzschild-de Sitter spacetime derived from 5D model

Non-perturbative approach valid on large cosmological scales

Abstract

We develop a non-perturbative formalism for scalar metric fluctuations from a 5D extended version of general relativity in vacuum. In this work we concentrate our efforts on calculations valid on large cosmological scales, which are the dominant during the inflationary phase of the universe. The resulting metric in this limit is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution. We calculate the spectrum of these fluctuations with an effective 4D Schwarzschild-de Sitter spacetime on cosmological scales, which is obtained after we make a static foliation on the non-compact extra coordinate. Our results show how the squared metric fluctuations of the primordial universe become scale invariant with the inflationary expansion.