Condensate of Massive Graviton and Dark Matter

TL;DR

This paper explores how a condensate of massive gravitons in bigravity theory can act as dark matter, linking spacetime anisotropy and primordial magnetic fields to cosmic structure formation.

Contribution

It introduces a novel interpretation of massive graviton condensates as dark matter within ghost-free bigravity, analyzing their effects on universe dynamics and structure formation.

Findings

Massive graviton condensate behaves as dark matter.

Spacetime anisotropy is key to dark matter origin.

Primordial magnetic fields can produce sufficient anisotropy.

Abstract

We study coherently oscillating massive gravitons in the ghost-free bigravity theory. This coherent field can be interpreted as a condensate of the massive gravitons. We first define the effective energy-momentum tensor of the coherent massive gravitons in a curved spacetime. We then study the background dynamics of the universe and the cosmic structure formation including the effects of the coherent massive gravitons. We find that the condensate of the massive graviton behaves as a dark matter component of the universe. From the geometrical point of view the condensate is regarded as a spacetime anisotropy. Hence, in our scenario, dark matter is originated from the tiny deformation of the spacetime. We also discuss a production of the spacetime anisotropy and find that the extragalactic magnetic field of a primordial origin can yield a sufficient amount for dark matter.