Partition function of N composite bosons

The partition function of composite bosons (“cobosons” for short) is calculated in the canonical ensemble, with the Pauli exclusion principle between their fermionic components included in an exact way through the finite temperature many-body formalism for composite quantum particles we recently developed. To physically understand the very compact result we obtain, we first present a diagrammatic approach to the partition function of N elementary bosons. We then show how to extend this approach to cobosons with Pauli blocking and interaction between their fermions. These diagrams provide deep insights on the structure of a coboson condensate, paving the way toward the determination of the critical parameters for their quantum condensation.