Overlap valence on 2 + 1 flavor domain wall fermion configurations with deflation and low-mode substitution
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The overlap fermion propagator is calculated on 2 þ 1 flavor domain-wall fermion gauge configurations on 163 32, 243 64 and 323 64 lattices. With hyper-cubic (HYP) smearing and low eigenmode deflation, it is shown that the inversion of the overlap operator can be expedited by 20 times for the 163 32 lattice and 80 times for the 323 64 lattice. The overhead cost for calculating eigenmodes ranges from 4.5 to 7.9 propagators for the above lattices. Through the study of hyperfine splitting, we found that the Oðm2a2Þ error is small and these dynamical fermion lattices can adequately accommodate quark mass up to the charm quark. A preliminary calculation of the low-energy constant mix which characterizes the discretization error of the pion made up of a pair of sea and valence quarks in this mixedaction approach is carried out via the scalar correlator with periodic and antiperiodic boundary conditions. It is found to be small which shifts a 300 MeV pion mass by 10 to 19 MeVon these sets of lattices. We have studied the signal-to-noise issue of the noise source for the meson and baryon. We introduce a new algorithm with Z3 grid source and low eigenmode substitution to study the many-to-all meson and baryon correlators. It is found to be efficient in reducing errors for the correlators of both mesons and baryons. With 64-point Z3 grid source and low-mode substitution, it can reduce the statistical errors of the light quark (m 200–300 MeV) meson and nucleon correlators by a factor of 3–4 as compared to the point source. The Z3 grid source itself can reduce the errors of the charmonium correlators by a factor of 3.