Is Bimetric Gravity Really Ghost Free?

TL;DR

This paper critically examines the Hamiltonian structure of bimetric gravity to assess whether it truly avoids ghost instabilities, finding that the theory likely contains an uneliminated ghost mode.

Contribution

The authors perform a detailed Hamiltonian analysis of bimetric gravity, challenging previous claims of its ghost-free nature by showing the absence of necessary constraints.

Findings

No additional constraints found to eliminate ghost mode

Bimetric gravity potentially contains a ghost instability

Questions the ghost-free claim of the theory

Abstract

We perform the Hamiltonian analysis of the bimetric theory of gravity introduced in [arXiv:1109.3515 [hep-th]]. We carefully analyze the requirement of the preservation of all constraints and we find that there is no additional constraint that could eliminate the ghost mode.