The role of vector fields in modified gravity scenarios

Abstract

Gravitational vector degrees of freedom typically arise in many examples of modified gravity models. We start to systematically explore their role in these scenarios, studying the effects of coupling gravitational vector and scalar degrees of freedom. We focus on set-ups that enjoy a Galilean symmetry in the scalar sector and an Abelian gauge symmetry in the vector sector. These symmetries, together with the requirement that the equations of motion contain at most two space-time derivatives, only allow for a small number of operators in the Lagrangian for the gravitational fields. We investigate the role of gravitational vector fields for two broad classes of phenomena that characterize modified gravity scenarios. The first is self-acceleration: we analyze in general terms the behavior of vector fluctuations around self-accelerating solutions, and show that vanishing kinetic terms of vector fluctuations lead to instabilities on cosmological backgrounds. The second phenomenon is the screening of long range fifth forces by means of Vainshtein mechanism. We show that if gravitational vector fields are appropriately coupled to a spherically symmetric source, they can play an important role for defining the features of the background solution and the scale of the Vainshtein radius. Our general results can be applied to any concrete model of modified gravity, whose low-energy vector and scalar degrees of freedom satisfy the symmetry requirements that we impose.

17 pages, no figures. v2: discussion improved, JCAP version

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Cited by in corpus (16)

• Cosmic Acceleration from Abelian Symmetry Breaking
• Cosmology in generalized Proca theories
• Effective gravitational couplings for cosmological perturbations in generalized Proca theories
• Extended Gauss-Bonnet gravities in Weyl geometry
• Screening fifth forces in generalized Proca theories
• On the 4D generalized Proca action for an Abelian vector field
• A small cosmological constant from Abelian symmetry breaking
• Anisotropic cosmological solutions in massive vector theories
• A scenario for inflationary magnetogenesis without strong coupling problem
• Cosmology in beyond-generalized Proca theories
• Quantum Stability of Generalized Proca Theories
• Suppression of matter couplings with a vector field in generalized Proca theories
• Horndeski extension of the minimal theory of quasidilaton massive gravity
• Absence of solid angle deficit singularities in beyond-generalized Proca theories
• Higher derivative SVT theories from Kaluza-Klein reductions of Horndeski theory
• Vector wormholes as conduits for matter interaction