  At stronger gauge-field couplings, the domain wall fermion (DWF) residual
mass, a measure of chiral symmetry breaking, grows rapidly. This measure is
largely due to near zero fermion eigenmodes of logarithm of the 4D transfer
matrix along the fifth dimension, and these eigenmodes increase rapidly at
strong coupling. To suppress these eigenmodes, we have added to the DWF path
integral a multiplicative weighting factor consisting of a ratio of
determinants of Wilson-Dirac fermions having a chirally twisted mass with a
large negative real component and a small imaginary chiral component. Numerical
results show that this weighting factor with an appropriate choice of twisted
masses significantly suppresses the residual mass while allowing adequate
topological tunneling.
