The quintom model with O(N) symmetry

We investigate the quintom model of dark energy in the generalized case where the corresponding canonical and phantom fields possess O(N) symmetries. Assuming exponential potentials we find that this O(N) quintom paradigm exhibits novel properties comparing to the simple canonical and phantom scenarios. In particular, we find that the universe cannot result in a quintessence-type solution with w > -1, even in the cases where the phantom field seems to be irrelevant. On the contrary, there are always late-time attractors which correspond to accelerating universes with w < -1 and with a recent crossing of the phantom divide, and for a very large area of the parameter space they are the only ones. This is in contrast with the previous simple quintom results, where an accelerating universe is a possible late-time stable solution but it is not guaranteed.