# Massive mimetic cosmology

## TL;DR

This paper explores the cosmological implications of a novel ghost-free massive gravity theory with mimetic dark matter, analyzing its effects on cosmic expansion, stability, and observational constraints.

## Contribution

It introduces and studies the first cosmological implications of a new ghost-free massive gravity theory with mimetic dark matter, including stability analysis and observational constraints.

## Key findings

- Graviton mass affects cosmic expansion as an effective negative cosmological constant, radiation, and curvature.
- Constraints on model parameters from observational bounds on radiation and curvature.
- Late-time acceleration requires an additional positive cosmological constant or dark energy.

## Abstract

We study the first cosmological implications of the mimetic theory of massive gravity recently proposed by Chamseddine and Mukhanov. This is a novel theory of ghost-free massive gravity which additionally contains a mimetic dark matter component. In an echo of other modified gravity theories, there are self-accelerating solutions which contain a ghost instability. In the ghost-free region of parameter space, the effect of the graviton mass on the cosmic expansion history amounts to an effective negative cosmological constant, a radiation component, and a negative curvature term. This allows us to place constraints on the model parameters---the graviton mass and the St\"uckelberg vacuum expectation value---by insisting that the effective radiation and curvature terms be within observational bounds. The late-time acceleration must be accounted for by a separate positive cosmological constant or other dark energy sector. We impose further constraints at the level of perturbations by demanding linear stability. We comment on the possibility of distinguishing this theory from $\Lambda$CDM with current and future large-scale structure surveys.