Light-Front Field Theory of Hot and Dense Quark Matter

Abstract

Abstract. Extending the concepts of light-front field theory to quantum statistics provides a novel approach towards nuclear matter under extreme conditions. Such conditions exist, e.g., in neutron stars or in the early stage of our universe. They are experimentally expected to occur in heavy ion collisions, e.g., at RHIC and accelerators to be build at GSI and CERN. Light-front field theory is particularly suited, since it is based on a relativistic Hamiltonian approach. It allows us to treat the perturbative as well as the nonperturbative regime of QCD and also correlations that emerge as a field of few-body physics and is important for hadronization. Last but not least the Hamiltonian approach is useful for nonequilibrium processes by utilizing, e.g., the formalism of nonequilibrium statistical operators. Finite temperature and the light-frontAt first sight, it seems difficult to define proper temperature T for a system "on the light-front", because there is no Lorentz transformation to the rest frame of an observer, who is holding the thermometer. Despite the fact that this is formally clarified by now (see Sect. 2), I would like to motivate, how temperature could survive "on the light-front". Consider the Fermi distribution for the canonical ensemble of a noninteracting gas in the instant formwhere k 0 on = + √ m 2 + k 2 is the on-shell energy of a one-particle state with respect to the medium frame. Let the velocity of the medium be given by the time-like vector u = (u 0 , u), where u 2 = 1. If the medium is at rest with respect to the observer, u = (1, 0). For convenience we introduce the momentum of the medium 1 P = M 0 u with P 2 = M 2 0 . Following Susskind [1] we now assume * Presented at Light-Cone 2004, Amsterdam, 16 -20 August 1 This can be done, e.g., before the thermodynamic limit, so that the mass of the noninteracting system M0 can be achieved by summing all the single-particle energies.