Holographic RG and Cosmology in Theories with Quasi-Localized Gravity

TL;DR

This paper explores the holographic renormalization group flow in brane theories with quasi-localized gravity, revealing a duality between the GRS and DGP models and providing insights into their long-distance behavior and radion dynamics.

Contribution

It demonstrates a holographic duality between the GRS and DGP models, elucidates the radion's role in long-distance gravity, and shows how holographic RG aids in understanding these theories.

Findings

At large scales, gravity transitions from 4D to 5D behavior.

The radion dominates at long distances, causing scalar anti-gravity.

The GRS model is holographically dual to the DGP model, with the radion canceling extra graviton polarization.

Abstract

We study the long distance behaviour of brane theories with quasi-localized gravity. The 5D effective theory at large scales follows from a holographic renormalization group flow. As intuitively expected, the graviton is effectively four dimensional at intermediate scales and becomes five dimensional at large scales. However in the holographic effective theory the essentially 4D radion dominates at long distances and gives rise to scalar anti-gravity. The holographic description shows that at large distances the GRS model is equivalent to the model recently proposed by Dvali, Gabadadze and Porrati (DGP), where a tensionless brane is embedded into 5D Minkowski space, with an additional induced 4D Einstein-Hilbert term on the brane. In the holographic description the radion of the GRS model is automatically localized on the tensionless brane, and provides the ghost-like field necessary to cancel the extra graviton polarization of the DGP model. Thus, there is a holographic duality between these theories. This analysis provides physical insight into how the GRS model works at intermediate scales; in particular it sheds light on the size of the width of the graviton resonance, and also demonstrates how the holographic RG can be used as a practical tool for calculations.