On the Cosmology of Massive Vector Fields with SO(3) Global Symmetry

The authors study the dynamics of flat Friedmann-Robertson-Walker cosmologies (FRW) in the presence of a triplet of massive vector fields with SO(3) global symmetry. They find an E3-symmetric ansatz for the vector fields that is compatible with the E3-invariant FRW metric and propose a method to make an invariant ansatz for more general cosmological models. They use the techniques of dynamical systems to study qualitatively the behaviour of the model and find, in particular, that the effective equation of state of the system changes gradually from a radiation-dominated to a matter-dominated form and that the scale of the transition depends on the mass of the gauge fields.