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A Unified Approach to Unimodality of Gaussian Polynomials

by Christoph Koutschan, Ali Uncu, Elaine Y Wong
Publication Type
Conference Paper
Book Title
ISSAC '23: Proceedings of the 2023 International Symposium on Symbolic and Algebraic Computation
Publication Date
Page Numbers
434 to 442
Issue
None
Publisher Location
New York, New York, United States of America
Conference Name
International Symposium on Symbolic and Algebraic Computation (ISSAC)
Conference Location
Tromsø, Norway
Conference Sponsor
ACM SIGSAM
Conference Date
-

In 2013, Pak and Panova proved the strict unimodality property of q-binomial coefficients (as polynomials in q) based on the combinatorics of Young tableaux and the semigroup property of Kronecker coefficients. They showed it to be true for all ℓ, m ≥ 8 and a few other cases. We propose a different approach to this problem based on computer algebra, where we establish a closed form for the coefficients of these polynomials and then use cylindrical algebraic decomposition to identify exactly the range of coefficients where strict unimodality holds. This strategy allows us to tackle generalizations of the problem, e.g., to show unimodality with larger gaps or unimodality of related sequences. In particular, we present proofs of two additional cases of a conjecture by Stanley and Zanello.