Conformally and Disformally Coupled Vector field Models of Dark Energy

Abstract

Scalar fields coupled to dark matter by conformal or disformal transformations give rise to a general class of scalar-tensor theories which leads to a rich phenomenology in a cosmological setting. While this possibility has been studied comprehensively in the literature for scalar fields, the vector case has been hardly treated. We build hence models based on vector fields conformally and disformally coupled to dark matter and derive explicitly the general covariant form of the interaction term in an independent way of the gravity theory, whereby this result can be applied to general vector-tensor theories. For concreteness, the standard Proca theory with a vector exponential potential is taken to describe the vector-tensor sector, and some specific coupling functions are assumed to study the cosmological background dynamics by dynamical system techniques. Despite of choosing such a minimalist form for the underlying theory, the parameter space is considerably enriched compared to the uncoupled case due to the novel interactions, leading to new branches of solutions for the vector equation of motion. Thus, different trajectories can exist in phase space depending on the coupling parameters associated to the conformal and disformal functions. From here, new emerging vector-dark matter scaling solutions, and renewed stable attractor points are found to drive the late-time accelerated expansion of the universe. As a first examination about instabilities issues, we derive general conditions to avoid classical instabilities in a more general setup of the theory. Numerical calculations are performed as well to investigate more quantitatively the impact of the conformal and disformal couplings on the cosmological background evolution. These effects depend essentially on the strength on the coupling parameters and, in some specific cases, on their associated signs.

26 pages, 18 figures. Accepted for publication in Physical Review D. New section IIIA added: stability analysis. Conclusions remain unchanged

References in corpus (26)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• Quantum Gravity at a Lifshitz Point
• Cosmology and the Fate of Dilatation Symmetry
• Resummation of Massive Gravity
• Cosmological Constraints from the SDSS Luminous Red Galaxies
• Supernova Constraints and Systematic Uncertainties from the First 3 Years of the Supernova Legacy Survey
• Exploring gravitational theories beyond Horndeski
• Vector Inflation
• Inflationary cosmology and the late-time accelerated expansion of the universe in non-minimal Yang-Mills-$F(R)$ gravity and non-minimal vector-$F(R)$ gravity
• Tension between the power spectrum of density perturbations measured on large and small scales
• Anisotropic Dark Energy: Dynamics of Background and Perturbations
• Interacting Vector-like Dark Energy, the First and Second Cosmological Coincidence Problems
• Can a vector field be responsible for the curvature perturbation in the Universe?
• Disformal couplings and the dark sector of the universe
• Testing coupled dark energy models with their cosmological background evolution
• A small cosmological constant from Abelian symmetry breaking
• Generalized SU(2) Proca Theory
• The problem with Proca: ghost instabilities in self-interacting vector fields
• A singularity problem for interacting massive vectors
• A Dark Energy model from Generalized Proca Theory
• Attractor Solution in Coupled Yang-Mills Field Dark Energy Models
• Disformal vectors and anisotropies on a warped brane
• Pervasiveness of the breakdown of self-interacting vector field theories
• Coupled dark energy model inspired from general conformal transformation
• The well-posedness of the Cauchy problem for self-interacting vector fields

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• I. Linear Interacting Dark Energy: Analytical Solutions and Theoretical Pathologies
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• Dynamical Shortcomings in the Generalized SU(2) Proca Theory: Challenges for Cosmic Acceleration
• Phantom cosmology with arbitrary potential: New accelerating scaling attractors
• Internal symmetry to the rescue: well-posed 1+1 evolution of self-interacting vector fields