  We study the dynamical behavior of a square lattice Ising model with exchange
and dipolar interactions by means of Monte Carlo simulations. After a sudden
quench to low temperatures we find that the system may undergo a coarsening
process where stripe phases with different orientations compete or
alternatively it can relax initially to a metastable nematic phase and then
decay to the equilibrium stripe phase through nucleation. We measure the
distribution of equilibration times for both processes and compute their
relative probability of occurrence as a function of temperature and system
size. This peculiar relaxation mechanism is due to the strong metastability of
the nematic phase, which goes deep in the low temperature stripe phase. We also
measure quasi-equilibrium autocorrelations in a wide range of temperatures.
They show a distinct decay to a plateau that we identify as due to a finite
fraction of frozen spins in the nematic phase. We find indications that the
plateau is a finite size effect. Relaxation times as a function of temperature
in the metastable region show super-Arrhenius behavior, suggesting a possible
glassy behavior of the system at low temperatures.
