On the health of a vector field with (R A^2)/6 coupling to gravity

Abstract

The coupling (R A^2)/6 of a vector field to gravity was proposed as a mechanism for generating a primordial magnetic field, and more recently as a mechanism for generating a statistically anisotropic contribution to the primordial curvature perturbation. In either case, the vector field's perturbation has both a transverse and a longitudinal component, and the latter has some unusual features which call into question the health of the theory. We calculate for the first time the energy density generated by the longitudinal field perturbations, and go on to argue that the theory may well be healthy in at least some versions.

11 pages

References in corpus (9)

• Vector Inflation
• Generation of Large-Scale Magnetic Fields in Single-Field Inflation
• Instability of anisotropic cosmological solutions supported by vector fields
• Can a vector field be responsible for the curvature perturbation in the Universe?
• Instability of the ACW model, and problems with massive vectors during inflation
• Anisotropic non-Gaussianity from vector field perturbations
• Cosmological perturbations from vector inflation
• Non-minimally coupled vector curvaton
• Gravitational waves in vector inflation

Cited by in corpus (15)

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• Non-minimally Coupled Vector Boson Dark Matter
• Dark Matter Candidates and Searches
• Experimental targets for dark photon dark matter
• Large-scale gauge spectra and pseudoscalar couplings
• On the degrees of freedom count on singular phase space submanifolds
• Minimal solution to the axion isocurvature problem from a nonminimal coupling
• The quantum origin of cosmic structure: theory and observations
• The hypermagnetic power spectra and the phases of Sakharov oscillations
• Vector dark matter production during inflation in the gradient-expansion formalism
• The Dark Photon: a 2026 Perspective