Critical Points in the QCD Phase Diagram with Two Flavors of Quarks

We employ the linear sigma model to study the chiral dynamics of two flavors of quarks at finite temperature and density. Our calculations include thermal fluctuations of both the bosonic and fermionic fields. In particular, we determine the phase diagram in the plane of temperature and baryon chemical potential as a function of the pion mass. An interesting phase structure occurs that results in zero, one, or two critical points depending on the value of the vacuum pion mass.