Frozen states of a disordered globular heteropolymer

The disordered heteropolymer chain with a random sequence of links-a simple model of globular protein-is investigated using the replica approach in the mean-field approximation. It is shown that for low dimensions of space (d<2) polymer bonds play the main role of creating frustrations. The mean-field equations are derived; the solution of these equations is obtained by the variational principle. This solution demonstrates the replica-symmetry breaking with unusual behaviour of the Parisi order parameter q(x) approximately x m for x<x 0 and m>1. It follows that the set of equilibrium states is ultrametric with an anomalously large number of weakly overlapping states.