Doubly-boosted vector cosmologies from disformal metrics

Abstract

A systematic dynamical system approach is applied to study the cosmology of anisotropic Bianchi I universes in which a vector field is assumed to operate on a disformal frame. This study yields a number of new fixed points, among which anisotropic scaling solutions. Within the simplifying assumption of (nearly) constant-slope potentials these are either not stable attractors, do not describe accelerating expansion or else they feature too large anisotropies to be compatible with observations. Nonetheless, some solutions do have an appeal for cosmological applications in that isotropy is retained due to rapid oscillations of the vector field.

Disformally coupled inflation

“…The same phenomenon was noted to occur also for a vector field residing upon a brane [43,44]. The sound speed of the other degree of freedom, c (φ) s , turns out to assume the more nontrivial form (3.3).…”

“…Note though that recently cosmology was studied with a vector field living on a brane, i.e. a (massive) vector coupled to a disformal metric given by a DBI type scalar field [43,44].…”

“…Kaloper [19] proposed a model with a disformal coupling of a massless inflaton to the Standard model, and found that such coupling could be well constrained by collider experiments such as the LHC, as confirmed by more recent studies [20,21], though these constraints can be avoided if the disformal coupling is suppressed in the Standard model sector after reheating. On the other hand, in the context of late-time cosmology and dark energy, aspects of disformal couplings such as the possible disformal screening mechanism [22,23] and its limitations [24,25], background dynamics [26][27][28], self-couplings [29,30], DIMP dark matter [11,31], structure formation [32][33][34], photon interactions [35][36][37] and astrophysical implications [38,39], have recently been investigated, see e.g. [40,41] for introductory treatments.…”

Disformal transformation in Newton–Cartan geometry

“…Noticing that the relativistic disformal transformation in the form g αβ = A(φ)g αβ + B(φ)φ α φ β is of particular interest in recent literature [23,24,[34][35][36][37][38][39][40], we will restrict our attention to the special case where the disformal parameters A, B, and C in (30) are only functions of the scalar field φ throughout this section.…”

“…varying speed of light models [25], inflation [26], dark energy models [27] and dark matter models [28]. In particular, it acts an important role in Horndeski theories and has led to many important results in modified gravity and cosmology [23,24,[29][30][31][32][33][34][35][36][37][38][39][40]. It is interesting to note that there are very few discussions as regards disformal transformation in the non-relativistic realm.…”