Towards a Theory of Binary Bound States in the Quark-Gluon Plasma

Although at asymptotically high temperatures the quark-gluon plasma (QGP) is a gas of weakly interacting quasiparticles (modulo long-range magnetism), it has quite different properties at temperatures of the order of few times the critical temperature $T=(1-3) T_c$. As experiments and lattice simulations are now showing, in this region the QGP displays strong interactions between the constituents. In this paper we try to develop a theory of one of its consequences, namely the properties of a large number of binary bound states, both hadron-like (colorless) and exotic (colored) bound pairs $gq, qq, gg$. We evaluate their binding energies and {\em zero binding lines} on the phase diagram, and estimate their contribution to bulk thermodynamics (pressure). Their role in the transport properties (viscosity), emphasized in our previous paper, will be addressed elsewhere.