Doubly-boosted vector cosmologies from disformal metrics

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 are 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. Such cosmological scenarios could describe physics beyond standard model such as extra dimensional models that predict disformal couplings between vector and scalar fields.