One loop fermion contribution to the effective potential for constant SU(2) Yang-Mills fields

We obtain a series expansion for the one loop fermion contribution to the effective potential for constant A^a_\mu fields in SU(2) theory with a massive fermionic doublet. The series converges for bounded electric fields in terms of the magnetic fields and the gauge potentials. One finds that spontaneous fermion pair creation may be absent for arbitrary strong pure electric fields, with an appropriate choice of the classical currents.