Limit distributions for Euclidean random permutations

Abstract: We study the length of cycles in the model of spatial random permutations in Euclidean space. In this model, for given length $L$, density $\rho$, dimension $d$ and jump density $\varphi$, one samples $\rho L^d$ particles in a $d$-dimensional torus of side length $L$, and a permutation $\pi$ of the particles, with probability density proportional to the product of values of $\varphi$ at the differences between a particle and its image under $\pi$. The distribution may be further weighted by a factor of $\theta$ to the number of cycles in $\pi$. Following Matsubara and Feynman, the emergence of macroscopic cycles in $\pi$ at high density $\rho$ has been related to the phenomenon of Bose-Einstein condensation. For each dimension $d\ge 1$, we identify sub-critical, critical and super-critical regimes for $\rho$ and find the limiting distribution of cycle lengths in these regimes. The results extend the work of Betz and Ueltschi. Our main technical tools are saddle-point and singularity analysis of suitable generating functions following the analysis by Bogachev and Zeindler of a related surrogate-spatial model.