Reconstructing Partitions from their Multisets of $k$-Minors

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 ${\hat{M}}_k(\lambda )$ 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 ${\lim }_{n\to \infty }G(n)/n=1$ 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 $\lambda$.

29 pages, 8 figures