Superconducting dark energy
  Based on the analogy with superconductor physics we consider a
scalar-vector-tensor gravitational model, in which the dark energy action is
described by a gauge invariant electromagnetic type functional. By assuming
that the ground state of the dark energy is in a form of a condensate with the
U(1) symmetry spontaneously broken, the gauge invariant electromagnetic dark
energy can be described in terms of the combination of a vector and of a scalar
field (corresponding to the Goldstone boson), respectively. The gravitational
field equations are obtained by also assuming the possibility of a non-minimal
coupling between the cosmological mass current and the superconducting dark
energy. The cosmological implications of the dark energy model are investigated
for a Friedmann-Robertson-Walker homogeneous and isotropic geometry for two
particular choices of the electromagnetic type potential, corresponding to a
pure electric type field, and to a pure magnetic field, respectively. The time
evolution of the scale factor, matter energy density and deceleration parameter
are obtained for both cases, and it is shown that in the presence of the
superconducting dark energy the Universe ends its evolution in an exponentially
accelerating vacuum de Sitter state. By using the formalism of the irreversible
thermodynamic processes for open systems we interpret the generalized
conservation equations in the superconducting dark energy model as describing
matter creation. The particle production rates, the creation pressure and the
entropy evolution are explicitly obtained.
