Strong coupling in brane-induced gravity in five dimensions

TL;DR

This paper analyzes the five-dimensional brane-induced gravity model, revealing an intrinsic intermediate energy scale and strong coupling at relatively short distances, which impacts its viability for explaining cosmic acceleration.

Contribution

It identifies an intrinsic energy scale and demonstrates the onset of strong coupling at short distances in the model, challenging its effectiveness for cosmological explanations.

Findings

The model has an intrinsic intermediate energy scale.

Strong coupling occurs at distances below tens of meters.

Implications for the model's use in explaining cosmic acceleration.

Abstract

Brane-induced gravity in five dimensions (Dvali--Gabadadze--Porrati model) exhibits modification of gravity at ultra-large distances, $r\gg r_c = M_{Pl}^2/M^3$ where $M$ is the five-dimensional gravity scale. This makes the model potentially interesting for explaining the observed acceleration of the Universe. We argue, however, that it has an intrinsic intermediate energy scale $(M^9/M_{Pl}^4)^{1/5}$. At higher energies, the model is strongly coupled. For $r_c$ of order of the present Hubble size, the strong coupling regime occurs at distanced below tens of metres.