- QCD with imaginary chemical potential is free of the sign problem and exhibits a rich phase structure constraining the phase diagram at real chemical potential. We simulate the critical end point of the Roberge- Weiss transition at imaginary chemical potential for Nf 1⁄4 2 QCD on Nτ 1⁄4 6 lattices with standard Wilson fermions. As found on coarser lattices, the Roberge-Weiss end point is a triple point connecting the deconfinement/chiral transitions in the heavy/light quark mass region and changes to a second-order end point for intermediate masses. These regimes are separated by two tricritical values of the quark mass, which we determine by extracting the critical exponent ν from a systematic finite size scaling analysis of the Binder cumulant of the imaginary part of the Polyakov loop. We are able to explain a previously observed finite size effect afflicting the scaling of the Binder cumulant in the regime of three-phase coexistence. Compared to Nτ 1⁄4 4 lattices, the tricritical masses are significantly shifted. Exploratory results on Nτ 1⁄4 8 as well as comparison with staggered simulations suggest that much finer lattices are needed before a continuum extrapolation becomes feasible.
Deutsches Urheberrecht