The Universality of the Resonance Arrangement and its Betti Numbers

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1. Verfasser: Kühne, Lukas
Format: Preprint
Veröffentlicht: 2020
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author Kühne, Lukas
author_facet Kühne, Lukas
contents The resonance arrangement $\mathcal{A}_n$ is the arrangement of hyperplanes which has all non-zero $0/1$-vectors in $\mathbb{R}^n$ as normal vectors. It is the adjoint of the Braid arrangement and is also called the all-subsets arrangement. The first result of this article shows that any rational hyperplane arrangement is the minor of some large enough resonance arrangement. Its chambers appear as regions of polynomiality in algebraic geometry, as generalized retarded functions in mathematical physics and as maximal unbalanced families that have applications in economics. One way to compute the number of chambers of any real arrangement is through the coefficients of its characteristic polynomial which are called Betti numbers. We show that the Betti numbers of the resonance arrangement are determined by a fixed combination of Stirling numbers of the second kind. Lastly, we develop exact formulas for the first two non-trivial Betti numbers of the resonance arrangement.
format Preprint
id arxiv_https___arxiv_org_abs_2008_10553
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle The Universality of the Resonance Arrangement and its Betti Numbers
Kühne, Lukas
Combinatorics
05B35, 52B40, 14N20, 52C35
The resonance arrangement $\mathcal{A}_n$ is the arrangement of hyperplanes which has all non-zero $0/1$-vectors in $\mathbb{R}^n$ as normal vectors. It is the adjoint of the Braid arrangement and is also called the all-subsets arrangement. The first result of this article shows that any rational hyperplane arrangement is the minor of some large enough resonance arrangement. Its chambers appear as regions of polynomiality in algebraic geometry, as generalized retarded functions in mathematical physics and as maximal unbalanced families that have applications in economics. One way to compute the number of chambers of any real arrangement is through the coefficients of its characteristic polynomial which are called Betti numbers. We show that the Betti numbers of the resonance arrangement are determined by a fixed combination of Stirling numbers of the second kind. Lastly, we develop exact formulas for the first two non-trivial Betti numbers of the resonance arrangement.
title The Universality of the Resonance Arrangement and its Betti Numbers
topic Combinatorics
05B35, 52B40, 14N20, 52C35
url https://arxiv.org/abs/2008.10553