Catalan numbers, parking functions, permutahedra and noncommutative Hilbert schemes

Abstract

We find an explicit $S_n$-equivariant bijection between the integral points in a certain zonotope in ${\mathbb{R}}^n$, combinatorially equivalent to the permutahedron, and the set of $m$-parking functions of length $n$. This bijection restricts to a bijection between the regular $S_n$-orbits and $(m,n)$-Dyck paths, the number of which is given by the Fuss-Catalan number $A_n(m,1)$. Our motivation came from studying tilting bundles on noncommutative Hilbert schemes. As a side result we use these tilting bundles to construct a semi-orthogonal decomposition of the derived category of noncommutative Hilbert schemes.

v2: Correct ERC funding acknowledgement