Tricritical point of lattice QCD with Wilson quarks at finite temperature and density

First principle study of QCD at finite temperature T and chemical potential μ is essential for understanding a wide range of phenomena from heavy-ion collisions to cosmology and neutron stars. However, in the presence of finite density, the critical behavior lattice gauge theory without species doubling, is unknown. At strong coupling, we examine the phase structure on the (μ, T ) plane, using Hamiltonian lattice QCD with Wilson fermions. A tricritical point is found, separating the first and second order chiral phase transitions. Such a tricritical point is absent in the Kogut-Susskind fermion or naive fermion cases.