S. Sarkar

Topological susceptibility in lattice QCD with unimproved Wilson fermions

Abstract We address a long standing problem regarding topology in lattice simulations of QCD with unimproved Wilson fermions. Earlier attempt with unimproved Wilson fermions at β = 5.6 to verify the suppression of topological susceptibility with decreasing quark mass ( m q ) was unable to unambiguously confirm the suppression. We carry out systematic calculations for two degenerate flavours at two different lattice spacings ( β = 5.6 and 5.8). The effects of quark mass, lattice volume and the lattice spacing on the spanning of different topological sectors are presented. We unambiguously demonstrate the suppression of the topological susceptibility with decreasing quark mass, expected from chiral Ward identity and chiral perturbation theory.

Exploring autocorrelations in two-flavor Wilson Lattice QCD using DD-HMC algorithm

a b s t r a c t We perform an extensive study of the autocorrelation of several observables in lattice QCD with two degenerate flavors of unimproved Wilson fermions and Wilson gauge action using the DD-HMC algorithm. We show that (1) at a given lattice spacing, autocorrelation of topological susceptibility and unsmeared plaquette show indication of a decrease with decreasing quark mass, (2) autocorrelation of topological susceptibility and topological charge density correlator increase with decreasing lattice spacing but the effect is milder in the latter case and (3) increasing the size and the smear level increase the autocorrelation of smeared Wilson loop.

Pion and nucleon in two flavour QCD with unimproved Wilson fermions

Abstract We calculate pion mass, pion decay constant, PCAC quark mass and nucleon mass in two flavour lattice QCD with unimproved Wilson fermion and gauge actions. Simulations are performed using DD-HMC algorithm at two lattice spacings and two volumes for several values of the quark mass. The cutoff effects in pion mass and nucleon mass for the explored region of parameter space are found to be negligible. We extract the average value of the up–down quark mass in the MS ¯ scheme at 2 GeV, which is in good agreement with the world data. The chiral behaviours of pion mass, pion decay constant and quark condensate are found to be qualitatively consistent with NLO chiral perturbation theory. The extracted values of the pion decay constant and the chiral condensate are in reasonable agreement with the world data.

Low lying hadron spectrum and chiral condensate with two flavours of naive Wilson fermions

We study low lying hadronic spectrum with two degenerate flavours of naive Wilson fermions and unimproved Wilson gauge action using DDHMC algorithm as a function of PCAC quark mass at two different lattice spacings and different volumes. The scaling violations of the pionic observables and the nucleon mass are found to be negligible. The chiral behaviour of different observables are compared with NLO chiral perturbation theory predictions. Using the chiral Ward identity we calculate chiral condensate and it is found to be compatible with NLO chiral perturbation theory prediction.