We argue that the distribution functions for quarks and gluons are computable at small x for sufficiently large nuclei, perhaps larger than can be physically realized.For such nuclei, we argue that weak coupling methods may be used. We show that the computation of the distribution functions can be recast as a many body problem with a modified propagator, a coupling constant which depends on the multiplicity of particles per unit rapidity per unit area, and for non-abelian gauge theories, some extra media dependent vertices. We explicitly compute the distribution function for gluons to lowest order, and argue how they may be computed in higher order.

Quantum chromodynamics (QCD) contains field configurations which can be characterized by a topological invariant, the winding number Q w . Configurations with nonzero Q w break the charge-parity (CP) symmetry of QCD. We consider a novel mechanism by which these configurations can separate charge in the presence of a background magnetic field -the "Chiral Magnetic Effect". We argue that sufficiently large magnetic fields are created in heavy ion collisions so that the Chiral Magnetic Effect causes preferential emission of charged particles along the direction of angular momentum. Since separation of charge is CP-odd, any observation of the Chiral Magnetic Effect could provide a clear demonstration of the topological nature of the QCD vacuum. We give an estimate of the effect and conclude that it might be observed experimentally.

We show that the gluon distribution function for very large nuclei may be computed for small transverse momentum as correlation functions of an ultraviolet finite two dimensional Euclidean field theory. This computation is valid to all orders in the density of partons per unit area, but to lowest order in α s . The gluon distribution function is proportional to 1/x, and the effect of the finite density of partons is to modify the dependence on transverse momentum for small transverse momentum.

We discuss two special limiting forms of QCD matter which may be produced at RHIC. We conclude from the available empirical evidence that an equilibrated, but strongly coupled Quark Gluon Plasma has been made in such collisions. We also discuss the growing body of evidence that its source is a Color Glass Condensate.