Fluctuations for the critical free Bose gas

Abstract

We study the critical free Bose gas from a probabilistic vantage with a focus on the three-dimensional case. We obtain the critical exponents. These exponents and the occurrence of macroscopic loops subtly depend on the geometry of the domain and the boundary conditions, contrary to the subcritical and supercritical case. In particular, the second term of the Minakshisundaram-Pleijel expansion determines the emergence of large loops. We furthermore obtain non-Gaussian limit laws for the fluctuations, governed by the regularized Fredholm determinant of the Green operator.