The even-odd anomalous tunneling effect

The analysis of the interacting fermion models with SU(2) symmetry indicates the different behaviour of the splittings of opposite parity lowest energy eigenstates for even and odd number of fermions. The imaginary time-dependent mean field approach reproduces the exact results only for the even number of particles. For the odd particle numbers, an introduction of the universal logarithmic term to the action integral is needed. The even-odd effect appears in a wide class of models with SU(2) symmetry and is connected with the presence of p4-terms in the classical large N limit. (author) 13 refs.; 3 figs