Mehen, T; Tiburzi, BC, *Quarks with twisted boundary conditions in the epsilon regime*,
Physical Review D, vol. 72 no. 1
(2005),
pp. 1-9 [0505014], [doi] .
**Abstract:**

*We study the effects of twisted boundary conditions on the quark fields in the epsilon regime of chiral perturbation theory. We consider the SU(2)LxSU(2)R chiral theory with nondegenerate quarks and the SU(3)LxSU(3)R chiral theory with massless up and down quarks and massive strange quarks. The partition function and condensate are derived for each theory. Because flavor-neutral Goldstone bosons are unaffected by twisted boundary conditions chiral symmetry is still restored in finite volumes. The dependence of the condensate on the twisting parameters can be used to extract the pion decay constant from simulations in the epsilon regime. The relative contribution to the partition function from sectors of different topological charge is numerically insensitive to twisted boundary conditions. © 2005 The American Physical Society.*