Reconstructing Partitions from their Multisets of $k$-Minors

TL;DR

This paper investigates the reconstructability of partitions from their multisets of $k$-minors, establishing a threshold function $G(n)$ that determines when reconstruction is possible, and explores related algebraic properties of excitation factors.

Contribution

It introduces the function $G(n)$ characterizing when partitions can be reconstructed from $k$-minors and analyzes the asymptotic behavior of $G(n)$, linking it to representation theory and symmetric functions.

Findings

Partitions are reconstructible from $k$-minors if and only if $k \\le G(n)$.

The function $G(n)$ satisfies $n-G(n) = O(n/\\log n)$ and $\\lim_{n o \\infty} G(n)/n = 1$.

Certain excitation factors can be expressed as linear combinations of elementary symmetric polynomials of hook lengths.

Abstract

For non-negative integers $n$ and $k$ with $n \ge k$, a {\em $k$-minor} of a partition $\lambda = [\lambda_1, \lambda_2, \dots]$ of $n$ is a partition $\mu = [\mu_1, \mu_2, \dots]$ of $n-k$ such that $\mu_i \le \lambda_i$ for all $i$. The multiset $\widehat{M}_k(\lambda)$ of $k$-minors of $\lambda$ is defined as the multiset of $k$-minors $\mu$ with multiplicity of $\mu$ equal to the number of standard Young tableaux of skew shape $\lambda / \mu$. We show that there exists a function $G(n)$ such that the partitions of $n$ can be reconstructed from their multisets of $k$-minors if and only if $k \le G(n)$. Furthermore, we prove that $\lim_{n \rightarrow \infty} G(n)/n = 1$ with $n-G(n) = O(n/\log n)$. As a direct consequence of this result, the irreducible representations of the symmetric group $S_n$ can be reconstructed from their restrictions to $S_{n-k}$ if and only if $k \le G(n)$ for the same function $G(n)$. For a minor $\mu$ of the partition $\lambda$, we study the excitation factor $E_\mu (\lambda)$, which appears as a crucial part in Naruse's Skew-Shape Hook Length Formula. We observe that certain excitation factors of $\lambda$ can be expressed as a $\mathbb{Q}[k]$-linear combination of the elementary symmetric polynomials of the hook lengths in the first row of $\lambda$ where $k = \lambda_1$ is the number of cells in the first row of $\lambda$.