Two-flavor lattice-QCD simulation in the ε regime with exact chiral symmetry

We perform lattice simulations of two-flavor QCD using Neuberger's overlap fermion, with which the exact chiral symmetry is realized at finite lattice spacings. The epsilon regime is reached by decreasing the light quark mass down to 3 MeV on a 16(3) X 32 lattice with a lattice spacing similar to 0.11 fin. We find a good agreement of the low-lying Dirac eigenvalue spectrum with the analytical predictions of the chiral random matrix theory, which reduces to the chiral perturbation theory in the epsilon regime. The chiral condensate is extracted as Sigma((MS) over bar)(2 GeV) = (251 +/- 7 +/- 11 MeV)(3), where the errors are statistical and an estimate of the higher order effects in the epsilon expansion.