Microcanonical versus canonical ensemble of bosons in a 1D harmonic trap

Abstract

We consider a fixed number of noninteracting bosons in a harmonic trap. The determination of the exact microcanonical ground state number fluctuation is a difficult enterprise. There have been several theoretical attempts to solve this problem approximately, especially in 1D models where analytic results were found using some asymptotic formulae from number theory. Here, we obtain the exact number fluctuation curves, and show that these exact curves are substantially different from the results presented in literature for small particle number and finite temperature. Further, we show how these approximate microcanonical results may be derived using a canonical thermodynamics approach.