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| Main Authors: | , , |
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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2502.08948 |
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| _version_ | 1866916793693503488 |
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| author | Ferroni, Luis Panova, Greta Venturello, Lorenzo |
| author_facet | Ferroni, Luis Panova, Greta Venturello, Lorenzo |
| contents | Every symmetric polynomial $h(x)$ with center of symmetry $n/2$ can be expressed as a linear combination in the basis $x^i(1+x)^{n-2i}$. The $γ$-polynomial of $h(x)$, which we denote $γ_h(x)$, records the coefficients of this linear combination. Two decades ago, Brändén and Gal independently showed that if $γ_h(x)$ has nonpositive real roots only, then so does $h(x)$. More recently, Brändén, Ferroni, and Jochemko proved using Lorentzian polynomials that if $γ_h(x)$ is ultra log-concave, then so is $h(x)$, and they raised the question of whether a similar statement can be proved for the usual notion of log-concavity. The purpose of this article is to show that the answer to the question of Brändén, Ferroni, and Jochemko is affirmative. One of the crucial ingredients of the proof is an inequality involving binomial numbers that we establish via a path-counting argument. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_08948 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Preservation of log-concavity on gamma polynomials Ferroni, Luis Panova, Greta Venturello, Lorenzo Combinatorics Every symmetric polynomial $h(x)$ with center of symmetry $n/2$ can be expressed as a linear combination in the basis $x^i(1+x)^{n-2i}$. The $γ$-polynomial of $h(x)$, which we denote $γ_h(x)$, records the coefficients of this linear combination. Two decades ago, Brändén and Gal independently showed that if $γ_h(x)$ has nonpositive real roots only, then so does $h(x)$. More recently, Brändén, Ferroni, and Jochemko proved using Lorentzian polynomials that if $γ_h(x)$ is ultra log-concave, then so is $h(x)$, and they raised the question of whether a similar statement can be proved for the usual notion of log-concavity. The purpose of this article is to show that the answer to the question of Brändén, Ferroni, and Jochemko is affirmative. One of the crucial ingredients of the proof is an inequality involving binomial numbers that we establish via a path-counting argument. |
| title | Preservation of log-concavity on gamma polynomials |
| topic | Combinatorics |
| url | https://arxiv.org/abs/2502.08948 |