Two flavor QCD and confinement

We argue that the order of the chiral transition for Nf=2 is a sensitive probe of the QCD vacuum, in particular, of the mechanism of color confinement. A strategy is developed to investigate the order of the transition by use of finite size scaling analysis. An in-depth numerical investigation is performed with staggered fermions on lattices with Lt=4 and Ls=12, 16, 20, 24, 32 and quark masses amq ranging from 0.01335 to 0.307036. The specific heat and a number of susceptibilities are measured and compared with the expectations of an O(4) second order and of a first order phase transition. A detailed comparison with previous works, which all use similar techniques as ours, is performed. A second order transition in the O(4) and O(2) universality classes are incompatible with our data, which seem to prefer a first order transition. However we have Lt=4 and unimproved action, so that a check with improved techniques (algorithm and action) and possibly larger Lt will be needed to assess this issue on a firm basis