The Vainshtein mechanism in the Decoupling Limit of massive gravity

TL;DR

This paper studies static solutions in nonlinear massive gravity, showing the decoupling limit can recover General Relativity solutions without singularities, revealing new scalings and implications for the Vainshtein mechanism.

Contribution

It demonstrates that the decoupling limit admits regular solutions with Vainshtein-like recovery, uncovering new scalings and questioning previous assumptions about singularities in massive gravity.

Findings

Decoupling limit solutions are regular and mimic GR.

New small-distance scaling associated with a zero mode.

Vainshtein mechanism can operate beyond traditional potentials.

Abstract

We investigate static spherically symmetric solutions of nonlinear massive gravities. We first identify, in an ansatz appropriate to the study of those solutions, the analog of the decoupling limit (DL) that has been used in the Goldstone picture description. We show that the system of equations left over in the DL has regular solutions featuring a Vainshtein-like recovery of solutions of General Relativity (GR). Hence, the singularities found to arise integrating the full nonlinear system of equations are not present in the DL, despite the fact those singularities are usually thought to be due to a negative energy mode also seen in this limit. Moreover, we show that the scaling conjectured by Vainshtein at small radius is only a limiting case in an infinite family of non singular solutions each showing a Vainshtein recovery of GR solutions below the Vainshtein radius but a different common scaling at small distances. This new scaling is shown to be associated with a zero mode of the nonlinearities left over in the DL. We also show that, in the DL, this scaling allows for a recovery of GR solutions even for potentials where the original Vainshtein mechanism is not working. Our results imply either that the DL misses some important features of nonlinear massive gravities or that important features of the solutions of the full nonlinear theory have been overlooked. They could also have interesting outcomes for the DGP model and related proposals.