  The phase diagram of the d=3 Hubbard model is calculated as a function of
temperature and electron density n_i, in the full range of densities between 0
and 2 electrons per site, using renormalization-group theory. An
antiferromagnetic phase occurs at lower temperatures, at and near the
half-filling density of <n_i> = 1. The antiferromagnetic phase is unstable to
hole or electron doping of at most 15%, yielding to two distinct "tau" phases:
for large coupling U/t, one such phase occurs between 30-35% hole or electron
doping, and for small to intermediate coupling U/t another such phase occurs
between 10-18% doping. Both tau phases are distinguished by non-zero hole or
electron hopping expectation values at all length scales. Under further doping,
the tau phases yield to hole- or electron-rich disordered phases. We have
calculated the specific heat over the entire phase diagram. The low-temperature
specific heat of the weak-coupling tau phase shows a BCS-type exponential
decay, indicating a gap in the excitation spectrum, and a cusp singularity at
the phase boundary. The strong-coupling tau phase, on the other hand, has
characteristics of BEC-type superconductivity, including a critical exponent
alpha approximately equal to -1, and an additional peak in the specific heat
above the transition temperature indicating pair formation. In the limit of
large Coulomb repulsion, the phase diagram of the tJ model is recovered.
