Self-tuning inflation

TL;DR

This paper proposes a multidimensional $f(R)$ gravity inflation model with a scalar field, featuring two expansion stages, quantum fluctuation effects, and a specific extra space metric that aligns with observational data.

Contribution

It introduces a self-tuning inflationary model based on multidimensional $f(R)$ gravity without small parameters, connecting extra dimensions to the Starobinsky model.

Findings

The model describes two stages of space expansion.

Quantum fluctuations generate inhomogeneous extra metrics.

A specific extra space metric reproduces the Starobinsky model.

Abstract

We develop an inflationary model without small parameters on the basis of multidimensional $f(R)$ gravity with a minimally coupled scalar field. The model is described by two stages of space expansion. The first one begins at energy scales about the D-dimensional Planck mass and ends with the de Sitter metric of our space and the maximally symmetric extra dimensions. In the following, the quantum fluctuations produce a wide set of inhomogeneous extra metrics in causally disconnected regions quickly generated in the de Sitter space. We find a specific extra space metric that leads to the effective Starobinsky model that fits the observational data.