Partition identities associated with $A_r$-Surface singularities
Pooneh Afsharijoo, Pedro D. González Pérez, Hussein Mourtada
TL;DR
This work connects $A_r$-surface singularities to combinatorial partition identities via arc Hilbert-Poincaré series. It introduces 3-colored partitions and a family $\mathcal{F}_r$, proving that the counts $F_r(n)$ are independent of $r$ for all $r\ge2$ and equal to the number of partitions in which the part $1$ can appear in 3 colors while other parts appear in 2 colors; the generating-series is given by $\sum_{n\ge0} F_r(n) q^n=\frac{\mathbf{H}^2}{(q)_1}$ with $\mathbf{H}=\prod_{j\ge1}(1-q^j)^{-1}$. The proof synthesizes arc-space geometry, conjectural descriptions of initial ideals for $A_{r-1}$ singularities, and intricate generating-series manipulations anchored in Durfee-rectangle frameworks and Gordon-type identities, yielding a unifying infinite family of partition identities tied to $A_r$-type singularities.
Abstract
We prove a family of partition identities involving integer partitions in three colors. The conditions imposed on the types of partitions appearing in these identities involve constraints that arise in the Rogers-Ramanujan and Andrews-Gordon identities, as well as in their recent extensions. The identities established in this paper are associated with the $A_r$ surface singularities via the arc HP-series, which provides a measure of singularities of algebraic varieties defined using arc spaces.
