Cyclic Sieving of Multisets with Bounded Multiplicity and the Frobenius Coin Problem

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Main Author: Armstrong, Drew
Format: Preprint
Published: 2025
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author Armstrong, Drew
author_facet Armstrong, Drew
contents The two subjects in the title are related via the specialization of symmetric polynomials at roots of unity. Let $f(z_1,\ldots,z_n)\in\mathbb{Z}[z_1,\ldots,z_n]$ be a symmetric polynomial with integer coefficients and let $ω$ be a primitive $d$th root of unity. If $d|n$ or $d|(n-1)$ then we have $f(1,\ldots,ω^{n-1})\in\mathbb{Z}$. If $d|n$ then of course we have $f(ω,\ldots,ω^n)=f(1,\ldots,ω^{n-1})\in\mathbb{Z}$, but when $d|(n+1)$ we also have $f(ω,\ldots,ω^n)\in\mathbb{Z}$. We investigate these three families of integers in the case $f=h_k^{(b)}$, where $h_k^{(b)}$ is the coefficient of $t^k$ in the generating function $\prod_{i=1}^n (1+z_it+\cdots+(z_it)^{b-1})$. These polynomials were previously considered by several authors. They interpolate between the elementary symmetric polynomials ($b$=2) and the complete homogeneous symmetric polynomials ($b\to\infty$). When $\gcd(b,d)=1$ with $d|n$ or $d|(n-1)$ we find that the integers $h_k^{(b)}=(1,ω,\ldots,ω^{n-1})$ are related to cyclic sieving of multisets with multiplicities bounded above by $b$, generalizing the well know cyclic sieving results for sets ($b=2$) and multisets ($b\to \infty$). When $\gcd(b,d)=1$ and $d|(n+1)$ we find that the integers $h_k^{(b)}(ω,ω^2,\ldots,ω^n)$ are related to the Frobenius coin problem with two coins. The case $\gcd(b,d)\neq 1$ is more complicated. At the end of the paper we combine these results with the expansion of $h_k^{(b)}$ in various bases of the ring of symmetric polynomials.
format Preprint
id arxiv_https___arxiv_org_abs_2502_00378
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Cyclic Sieving of Multisets with Bounded Multiplicity and the Frobenius Coin Problem
Armstrong, Drew
Combinatorics
Representation Theory
The two subjects in the title are related via the specialization of symmetric polynomials at roots of unity. Let $f(z_1,\ldots,z_n)\in\mathbb{Z}[z_1,\ldots,z_n]$ be a symmetric polynomial with integer coefficients and let $ω$ be a primitive $d$th root of unity. If $d|n$ or $d|(n-1)$ then we have $f(1,\ldots,ω^{n-1})\in\mathbb{Z}$. If $d|n$ then of course we have $f(ω,\ldots,ω^n)=f(1,\ldots,ω^{n-1})\in\mathbb{Z}$, but when $d|(n+1)$ we also have $f(ω,\ldots,ω^n)\in\mathbb{Z}$. We investigate these three families of integers in the case $f=h_k^{(b)}$, where $h_k^{(b)}$ is the coefficient of $t^k$ in the generating function $\prod_{i=1}^n (1+z_it+\cdots+(z_it)^{b-1})$. These polynomials were previously considered by several authors. They interpolate between the elementary symmetric polynomials ($b$=2) and the complete homogeneous symmetric polynomials ($b\to\infty$). When $\gcd(b,d)=1$ with $d|n$ or $d|(n-1)$ we find that the integers $h_k^{(b)}=(1,ω,\ldots,ω^{n-1})$ are related to cyclic sieving of multisets with multiplicities bounded above by $b$, generalizing the well know cyclic sieving results for sets ($b=2$) and multisets ($b\to \infty$). When $\gcd(b,d)=1$ and $d|(n+1)$ we find that the integers $h_k^{(b)}(ω,ω^2,\ldots,ω^n)$ are related to the Frobenius coin problem with two coins. The case $\gcd(b,d)\neq 1$ is more complicated. At the end of the paper we combine these results with the expansion of $h_k^{(b)}$ in various bases of the ring of symmetric polynomials.
title Cyclic Sieving of Multisets with Bounded Multiplicity and the Frobenius Coin Problem
topic Combinatorics
Representation Theory
url https://arxiv.org/abs/2502.00378