Nicolas Macris (EPF Lausanne), Bruno Nachtergaele (Princeton U)
On the flux phase conjecture at half-filling: an improved proof
(54K, Latex + epsf.sty, 3 eps figures.)

ABSTRACT.  We present a simplification of Lieb's proof of the flux phase
conjecture for interacting fermion systems --- such as the Hubbard
model ---, at half filling on a general class of graphs.  The main
ingredient is a procedure which transforms a class of fermionic
Hamiltonians into reflection positive form.  The method can also be
applied to other problems, which we briefly illustrate with two
examples concerning the $t-V$ model and an extended Falicov-Kimball
model.