When do Schubert polynomial products stabilize?

Fuente: arXiv
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Autori principali: Hardt, Andrew, Wallach, David
Natura: Preprint
Pubblicazione: 2024
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author Hardt, Andrew
Wallach, David
author_facet Hardt, Andrew
Wallach, David
contents The "back-stabilization number" for products of Schubert polynomials is the distance the corresponding permutations must be shifted before the structure constants stabilize. We give an explicit formula for this number and thereby prove a conjecture of N. Li in a strengthened form. This leads to an additional result: a formula for the smallest $n$ such that a given Schubert product expands completely over $S_n$. Our method is to explore back-stable fundamental slide polynomials and their products combinatorially, in the context of their associated words. We use three main tools: (i) an algebra consisting of "colored words", with a modified shuffle product, and which contains the rings of back (quasi)symmetric functions as subquotients; (ii) the combinatorics of increasing suffixes of reduced words; and (iii) the lift of differential operators to the space of colored words.
format Preprint
id arxiv_https___arxiv_org_abs_2412_06976
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle When do Schubert polynomial products stabilize?
Hardt, Andrew
Wallach, David
Combinatorics
14N15, 05E14
The "back-stabilization number" for products of Schubert polynomials is the distance the corresponding permutations must be shifted before the structure constants stabilize. We give an explicit formula for this number and thereby prove a conjecture of N. Li in a strengthened form. This leads to an additional result: a formula for the smallest $n$ such that a given Schubert product expands completely over $S_n$. Our method is to explore back-stable fundamental slide polynomials and their products combinatorially, in the context of their associated words. We use three main tools: (i) an algebra consisting of "colored words", with a modified shuffle product, and which contains the rings of back (quasi)symmetric functions as subquotients; (ii) the combinatorics of increasing suffixes of reduced words; and (iii) the lift of differential operators to the space of colored words.
title When do Schubert polynomial products stabilize?
topic Combinatorics
14N15, 05E14
url https://arxiv.org/abs/2412.06976