arXiv subjects
Publications and source records attributed to Lukas Gonglach.
We investigate the properties of the finite-temperature QCD transition towards the chiral limit using staggered quarks. Starting from the 2+1-flavor physical point, the limit of massless quarks is approached along two different trajectories in the Columbia-plot. Unlike in previous approaches, the chiral condensate is determined via the Banks-Casher relation. The first results of our finite size scaling analysis are presented.
For field theories with a topological charge Q, it is often of interest to measure the topological susceptibility chi_t = ( < Q^2 > - < Q >^2 ) / V. If we manage to perform a Monte Carlo simulation where Q changes frequently, chi_t can be evaluated directly. However, for local update algorithms and fine lattices, the auto-correlation time with respect to Q tends to be extremely long, which invalidates the direct approach. Nevertheless, the measurement of chi_t is still feasible, even when the entire Markov chain is topologically frozen. We test a method for this purpose, based on the correlation of the topological charge density, as suggested by Aoki, Fukaya, Hashimoto and Onogi. Our studies in non-linear sigma-models and in 2d Abelian gauge theory yield accurate results for chi_t, which confirm that the method is applicable. We also obtain promising results in 4d SU(2) Yang-Mills theory, which suggest the applicability of this method in QCD.