Abstract

In the context of massive (bi-)gravity, non-minimal matter couplings have been proposed. These couplings are special in the sense that they are free of the Boulware-Deser ghost below the strong coupling scale and can be used consistently as an effective field theory. Furthermore, they enrich the phenomenology of massive gravity. We consider these couplings in the framework of bimetric gravity and study the cosmological implications for background and linear tensor, vector, and scalar Previous works have investigated special branches of solutions. Here we perform a complete perturbation analysis for the general background equations of motion, completing previous analyses.

Highlights

  • In the context of quantum stability of the theory, new ways of coupling the matter fields have been explored [41–43]

  • We investigate the cosmological perturbation analysis of the bimetric theory with a scalar field coupled simultaneously to both metrics in terms of a composite metric

  • The scalar field represents the matter field that lives on both metrics

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Summary

Dynamical composite metric

A consistent coupling of some extra scalar field φ to both metrics simultaneously was introduced in [41] through a composite metric gμν gμν. + β2fμν , with μ ν defined by μλX gμλ fλν. Where R[g] and R[f ] are Ricci scalar for gμν and fμν, respectively. As in [56], in this work we consider the matter contents of gμν and fμν metrics to be two cosmological constant: Lmatter[g] = −Mg2 Λg and Lmatter[f ] = −Mf2 Λf. Are the elementary symmetric polynomials defined by en (M ) ≡ n!M[μμ[11] Mμμ22 · · · Mμμnn],. In (2.7), Xdenoting the canonical kinetic term of φ in terms of the composite metric. In the following we will study this action on FLRW background and establish our parametrization for linear perturbations

Cosmological parametrization
Nf2 γi2j k2 a2f γi2j
Ng d dt af Hf β2 α2 ag Hg Hf2
Conclusion
A Expressions of Ξab

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