Residual mass effects in improved domain wall fermions

In order to improve simulations with domain wall fermions (DWFs), it has been suggested to project out a number of low-lying eigenvalues of the 4-dimensional Dirac operator that generates the transfer matrix of DWF. We investigate how this projection method affects chiral properties of quenched DWF. In particular, we study the behaviour of the residual mass as a function of the size of the extra dimension.