Confinement-deconfinement phase transition at nonzero chemical potential

Abstract

We present arguments suggesting that large size overlapping instantons are the driving mechanism of the confinement-deconfinement phase transition in QCD at nonzero chemical potential $\ensuremath{\mu}$. The arguments are based on the picture that instantons at very large chemical potential in the weak coupling regime are localized configurations with finite size $\ensuremath{\rho}\ensuremath{\sim}{\ensuremath{\mu}}^{\ensuremath{-}1}$. At the same time, the same instantons at smaller chemical potential in the strong coupling regime are well represented by the so-called instanton-quarks with fractional topological charge $1/{N}_{c}$. We estimate the critical chemical potential ${\ensuremath{\mu}}_{c}(T)$ where this phase transition takes place as a function of temperature in the domain where our approach is justified. In this picture, the long standing problem of the ``accidental'' coincidence of the chiral and deconfinement phase transitions at nonzero temperature (observed in lattice simulations) is naturally resolved. We also derive results at nonzero isospin chemical potential ${\ensuremath{\mu}}_{I}$ where direct lattice calculations are possible, and our predictions can be explicitly tested.