Dark aspects of massive spinor electrodynamics
  We investigate the cosmology of massive spinor electrodynamics when torsion
is non-vanishing. A non-minimal interaction is introduced between the torsion
and the vector field and the coupling constant between them plays an important
role in subsequential cosmology. It is shown that the mass of the vector field
and torsion conspire to generate dark energy and pressureless dark matter, and
for generic values of the coupling constant, the theory effectively provides an
interacting model between them with an additional energy density of the form
$\sim 1/a^6$. The evolution equations mimic $\Lambda$CDM behavior up to $1/a^3$
term and the additional term represents a deviation from $\Lambda$CDM. We show
that the deviation is compatible with the observational data, if it is very
small. We find that the non-minimal interaction is responsible for generating
an effective cosmological constant which is directly proportional to the mass
squared of the vector field and the mass of the photon within its current
observational limit could be the source of the dark energy.
