More on ghosts in DGP model

TL;DR

The paper demonstrates that the self-accelerating solution in the DGP model contains a ghost mode, questioning its physical viability, and draws parallels with an Abelian gauge theory with Stueckelberg fields.

Contribution

It provides an explicit calculation showing the presence of a ghost in the DGP model's self-accelerating solution and highlights its similarity to an Abelian gauge theory.

Findings

The excitations around the self-accelerating solution contain a ghost mode.

The analysis reveals a similarity to an Abelian gauge model with Stueckelberg fields.

Raises doubts about the viability of the DGP model's self-accelerating solution.

Abstract

It is shown by an explicit calculation that the excitations about the self-accelerating cosmological solution of the Dvali--Gabadaze--Porrati model contain a ghost mode. This raises serious doubts about viability of this solution. Our analysis reveals the similarity between the quadratic theory for the perturbations around the self-accelerating Universe and an Abelian gauge model with two Stueckelberg fields.