  A fundamental constant in systems of unitary fermions is the so-called
Bertsch parameter, the ratio of the ground state energy for spin paired unitary
fermions to that for free fermions at the same density. I discuss how we
computed this parameter as well as the pairing gap using a recently developed
lattice construction for unitary fermions, by measuring correlation functions
for up to 38 fermions in a finite box. Our calculation illustrates interesting
issues facing the study of many-body states on the lattice, which may
eventually be confronted in QCD calculations as well.
