One-loop fermion determinant with explicit chiral symmetry breaking

We use a proper-time regularization to define the real part of the one-loop fermion determinant for the case in which explicit chiral symmetry breaking takes place. We demonstrate that beyond the chiral limit the standard definition of Re[lndetD] by ln|detD| deforms the symmetry breaking pattern of the basic fermionic Lagrangian. We show how to obtain the correcting functional in order to arrive at the fermion determinant whose transformation properties are consistent with the general symmetry requirements. As an example it is shown how the fundamental symmetries and the explicit chiral symmetry breaking pattern associated with the ENJL model are consistently preserved in this way.