Could dark energy be vector-like?

By C. Armendariz-Picon. 2004

260 citations recorded by the source corpus.

In this paper I explore whether a vector field can be the origin of the present stage of cosmic acceleration. In order to avoid violations of isotropy, the vector has be part of a 'cosmic triad', that is, a set of three identical vectors pointing in mutually orthogonal spatial directions. A triad is indeed able to drive a stage of late accelerated expansion in the universe, and there exist tracking attractors that render cosmic evolution insensitive to initial conditions. However, as in most other models, the onset of cosmic acceleration is determined by a parameter that has to be tuned to reproduce current observations. The triad equation of state can be sufficiently close to minus one today, and for tachyonic models it might be even less than that. I briefly analyse linear cosmological perturbation theory in the presence of a triad. It turns out that the existence of non-vanishing spatial vectors invalidates the decomposition theorem, i.e. scalar, vector and tensor perturbations do not decouple from each other. In a simplified case it is possible to analytically study the stability of the triad along the different cosmological attractors. The triad is classically stable during inflation, radiation and matter domination, but it is unstable during (late time) cosmic acceleration. I argue that this instability is not likely to have a significant impact at present.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/92d1ec53ff5d3ff140f288f5c65a5b886efb1e32

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Citations in the corpus

Vector inflation (2008, background): “3 Inflation Let us first consider a triplet of mutually orthogonal vector fields B (a) i [5], with the same magnitude |B| each.”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, background): “In all these considerations in order to guarantee an isotropic expansion, one has to either assume a large number of randomly oriented vector fields, or a triplet of orthogonal vector fields [240] or a vector field with only the zero component non-vanishing [241] (massive vector field).”
Accelerating Cosmologies with an Anisotropic Equation of State (2007, background): “In the RW case all the diagonal components of T ij should be equal, which indeed requires three vector fields, one in each coordinate direction, of exactly equal magnitudes, as the triads of ArmendarizPicon(Armendariz-Picon 2004).”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, methodology): “Approaches to deal with the anisotropy have been based on a “triad” of three identical vectors aligned with the three axis (Armendariz-Picon 2004), a large number of randomly oriented fields averaging to isotropy (Golovnev et al.”
Perturbations in Chromo-Natural Inflation (2013, background): “However, many of these vector models [37, 38, 40, 41], though not [42], are inherently unstable [43–46].”
New physics in light of the H0 tension: An alternative view (2019, background): “An example of one such model is the vector-like dark energy model constructed in [322].”
Vector field models of inflation and dark energy (2008, methodology): “RW metric all the diagonal components of Ti j should be equal, which then requires three vector ﬁelds, one in each coordinate direction, of exactly equal magnitudes, as the triads of Armendariz-Picon [14]. With the metric Eq.(6), the only constraint is that every vector ﬁeld should be along a coordi”