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Bimetric gravity doubly coupled to matter: theory and cosmological implications

Yashar Akrami, Tomi S. Koivisto, David F. Mota, Marit Sandstad

Abstract

A ghost-free theory of gravity with two dynamical metrics both coupled to matter is shown to be consistent and viable. Its cosmological implications are studied, and the models, in particular in the context of partially massless gravity, are found to explain the cosmic acceleration without resorting to dark energy.

Bimetric gravity doubly coupled to matter: theory and cosmological implications

Abstract

A ghost-free theory of gravity with two dynamical metrics both coupled to matter is shown to be consistent and viable. Its cosmological implications are studied, and the models, in particular in the context of partially massless gravity, are found to explain the cosmic acceleration without resorting to dark energy.

Paper Structure

This paper contains 20 sections, 45 equations.

Table of Contents

  1. Introduction
  2. The doubly-coupled bimetric gravity
  3. Theory
  4. Bianchi constraints
  5. Matter equations of motion and differences to two copies of GR
  6. On an ambiguity in defining a physical metric
  7. The homogeneous and isotropic universe
  8. Metrics and Bianchi constraints
  9. Generalised field equations and matter equations of motion
  10. Late-time universe and cosmic acceleration
  11. The case of dust only
  12. Emergent cosmological constant and $\Lambda$CDM regime
  13. Special parameter regimes
  14. One non-zero $B$ parameter
  15. $B_1 \neq 0$ and $\alpha \neq 0$
  16. ...and 5 more sections