Large Nc QCD phase diagram at µB = 0 on the lattice

Quantum-Chromodynamics (QCD) is a fundamental theory of strong interactions of quarks and gluons, the building blocks of composite particles, generically called hadrons (familiar proton, neutron,...), that are constituents of atomic nuclei. Individual quarks and gluons are never observed in our world, a property of QCD that is called confinement. They are confined within observable hadrons. QCD has an approximate symmetry, called chiral symmetry, which is related with a very small mass of some quarks. In hadrons this chiral symmetry is spontaneously broken. A fundamental question of QCD which is not yet answered, is the interrelation of confinement and spontaneous breaking of chiral symmetry. It is believed that at the very large temperatures, like during the first second of the existence of the Universe, the property of confinement is lost and instead of the individual hadrons we have the quark-gluon plasma phase with liberated fundamental QCD degrees of freedom. Such a state of matter can be created in the largest world laboratory, CERN, during the high energy collisions of atomic nuclei. At the same time the spontaneously broken chiral symmetry gets restored. It was previously thought that the deconfinement and chiral symmetry restoration happen together. Recently there appeared evidence that actually deconfinement transition takes place at a temperature that is essentially higher than the chiral restoration temperature. If so, there should be a third state of the strongly interacting matter, called stringy fluid, just between the hadronic phase at low temperatures and the quark gluon plasma phase at the very high temperatures. The aim of the present project is to establish these two temperatures in computer simulations of QCD on the lattice with the input parameters of QCD, such as the number of fundamental species of quarks and gluons, called colours, to be set to infinity, and the mass of quarks to be set to zero.