Recent Developments of Domain-wall/Overlap Fermions for Lattice QCD

I review the lattice formulations of vector-like gauge theories (e.g. QCD) with domain-wall/overlap fermions, and discuss how to optimize the chiral symmetry for any finite $ N_s $ (sites in the fifth dimension). In this formulation, quark propagators in gauge background can be computed efficiently through the effective 4D lattice Dirac operator.