Taylor- and fugacity expansion for the effective Z(3) spin model of QCD   at finite density
  Series expansions in the chemical potential mu are studied for an effective theory of QCD which has a flux representation where the complex action is overcome. In particular we consider fugacity series, Taylor expansion and a modified Taylor expansion and compare the outcome of these series to the reference results from a Monte Carlo simulation in the flux representation where arbitrary mu is accessible. It is shown that for most parameter values the fugacity expansion gives the best approximation to the data from the flux simulation, followed by our newly proposed modified Taylor expansion. For the conventional Taylor expansion we find that the results coincide with the flux data only for very small mu. 
Eva Gr\"unwald, Ydalia Delgado Mercado, Christof Gattringer
hep-lat hep-ph