# Gravitational Wave Oscillations in Bigravity

## TL;DR

This paper develops a theoretical framework for gravitational wave oscillations in bigravity, predicting observable effects similar to neutrino oscillations and providing new constraints on graviton properties.

## Contribution

It derives consistent equations for gravitational wave oscillations in bigravity, highlighting the basis difference between wave propagation and detection, and discusses phenomenological implications.

## Key findings

- Predicted oscillatory behavior of gravitational waves in bigravity.
- Derived new limits on graviton mass and coupling parameters.
- Highlighted potential observational signatures in gravitational wave data.

## Abstract

We derive consistent equations for gravitational wave oscillations in bigravity. In this framework a second dynamical tensor field is introduced in addition to General Relativity and coupled such that one massless and one massive linear combination arise. Only one of the two tensors is the physical metric coupling to matter, and thus the basis in which gravitational waves propagate is different from the basis where the wave is produced and detected. Therefore, one should expect -- in analogy to neutrino oscillations -- to observe an oscillatory behavior. We show how this behavior arises explicitly, discuss phenomenological implications and present new limits on the graviton parameter space in bigravity.