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seminar:pj_con_part

« Seminar

Reconstructing Partitions from their Multisets of $k$-Minors

Pakawut Jiradilok
Graduate Program, MIT, Boston, USA

16:00 Wednesday, 21 June 2017, Room 3306, MUIC

Abstract

For non-negative integers $n$ and $k$ with $n \ge k$, a $k$-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 $\lambda$.

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Last modified: 2017/07/05 10:42