Large mass invariant asymptotics of the effective action - art. no. 087701

We study the large mass asymptotics of the Dirac operator with a nondegener ate mass matrix m = diag(m(1), m(2), m(3)) in the presence of scalar and ps eudoscalar background fields taking values in the Lie algebra of the U(3) g roup. The corresponding one-loop effective action is regularized by Schwing er's proper-time technique. Using a well-known operator identity, we obtain a series representation for the heat kernel that differs from the standard proper-time expansion, if m(1) not equal m(2) not equal m(3). After integr ating over the proper time we use a new algorithm to resum the series. The invariant coefficients that define the asymptotics of the effective action are calculated up to the fourth order and compared with the related Seeley- DeWitt coefficients for the particular case of a degenerate mass matrix wit h m(1) = m(2) = m(3).