  SU(2) lattice gauge theory with four flavors of quarks is simulated at
nonzero chemical potential $\mu$ and temperature $T$ and the results are
compared to the predictions of Effective Lagrangians. Simulations on $16^4$
lattices indicate that at zero $T$ the theory experiences a second order phase
transition to a diquark condensate state. Several methods of analysis,
including equation of state fits suggested by Chiral Perturbation Theory,
suggest that mean-field scaling describes this critical point. Nonzero $T$ and
$\mu$ are studied on $12^3 \times 6$ lattices. For low $T$, increasing $\mu$
takes the system through a line of second order phase transitions to a diquark
condensed phase. Increasing $T$ at high $\mu$, the system passes through a line
of first order transitions from the diquark phase to the quark-gluon plasma
phase. Metastability is found in the vicinity of the first order line. There is
a tricritical point along this line of transitions whose position is consistent
with theoretical predictions.
