  We study the cold and dense regime in the phase diagram of two-color QCD with
heavy quarks within a three-dimensional effective theory for Polyakov loops.
This theory is derived from two-color QCD in a combined strong-coupling and
hopping expansion. In particular, we study the onset of diquark density as the
finite-density transition of the bosonic baryons in the two-color world. In
contrast to previous studies of heavy dense QCD, our zero-temperature
extrapolations are consistent with a continuous transition without binding
energy. They thus provide evidence that the effective theory for heavy quarks
is capable of describing the characteristic differences between diquark
condensation in two-color QCD and the liquid-gas transition of nuclear matter
in QCD.
