Finite-size effects on the phase transition in a four- and six-fermion   interaction model
  We consider four- and six-fermion interacting models at finite temperature and density. We construct the corresponding free energies and investigate the appearance of first- and second-order phase transitions. Finite-size effects on the phase structure are investigated using methods of quantum field theory on toroidal topologies 
L.M. Abreu, F.C. Khanna, A.P.C. Malbouisson, J.M.C. Malbouisson, A.E.   Santana
hep-th cond-mat.stat-mech hep-ph