Limit Shape of Minimal Difference Partitions and Fractional Statistics

The class of minimal difference partitionsMDP(q) (with gap q) is defined by the condition that successive parts in an integer partition differ from one another by at least q≥0. In a recent series of papers by A. Comtet and collaborators, the MDP(q) ensemble with uniform measure was interpreted as a combinatorial model for quantum systems with fractional statistics, that is, interpolating between the classical Bose–Einstein (q=0) and Fermi–Dirac (q=1) cases. This was done by formally allowing values q∈(0,1) using an analytic continuation of the limit shape of the corresponding Young diagrams calculated for integer q. To justify this “replica-trick”, we introduce a more general model based on a variable MDP-type condition encoded by an integer sequence q=(qi), whereby the (limiting) gap q is naturally interpreted as the Cesàro mean of q. In this model, we find the family of limit shapes parameterized by q∈[0,∞) confirming the earlier answer, and also obtain the asymptotics of the number of parts.