Strong Coupling vs. 4-D Locality in Induced Gravity

TL;DR

This paper investigates the strong coupling problem in a regularized DGP gravity model, finding it avoids strong coupling and ghosts up to cubic order, possibly due to its nonlocal nature, with implications for higher-order behavior.

Contribution

It demonstrates that a specific regularization of DGP gravity does not exhibit strong coupling or ghosts up to cubic order, contrasting with previous models.

Findings

Regularized model avoids strong coupling up to cubic order

No ghosts observed up to cubic order

Nonlocality may explain the improved behavior

Abstract

We re-examine the problem of strong coupling in a regularized version of DGP (or ``brane-induced'') gravity. We find that the regularization of ref. hep-th/0304148 differs from DGP in that it does not exhibit strong coupling or ghosts up to cubic order in the interactions. We suggest that the nonlocal nature of the theory, when written in terms of the 4-D metric, is a plausible reason for this phenomenon. Finally, we briefly discuss the possible behavior of the model at higher-order in perturbation theory.