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Annals of Combinatorics· 2026Q2

Extendability of the $$B_2$$-Arrangement

Torsten Hoge, Shota Maehara, Sven Wiesner

Short summary

Researchers found that for the Coxeter arrangement of type B2, infinitely many multiplicities exist for which no free extension is possible, unlike the A2 type.

AI-generated from the title and abstract; the full text is not read.

Key points

  • The study focuses on free extensions of multiarrangements, specifically the Coxeter arrangement of type B2.
  • Unlike the A2 arrangement where free extensions always exist, B2 arrangements have infinite multiplicities without free extensions.
  • This result impacts the general understanding of free extensions in higher-rank arrangements.

AI-generated from the title and abstract; the full text is not read.

Abstract

Abstract Let $$({\mathscr {A}},m)$$ ( A , m ) be a free multiarrangement, and let $${\mathscr {E}}$$ E be an extension of $$({\mathscr {A}},m)$$ ( A , m ) . It is well known that if $${\mathscr {A}}$$ A is the Coxeter arrangement of type $$A_2$$ A 2 , then a free extension of $$({\mathscr {A}},m)$$ ( A , m ) always exists. In this work, we demonstrate that if $${\mathscr {A}}$$ A is the Coxeter arrangement of type $$B_2$$ B 2 , there exist infinitely many multiplicities for which no free extension of $$({\mathscr {A}},m)$$ ( A , m ) exists. This result has immediate consequences for the existence of free extensions in higher rank.

The authors' abstract, as published at the source. Annals of Combinatorics, 2026 · DOI ↗

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Field: Discrete Mathematics and Combinatorics

Discrete Mathematics and CombinatoricsMathematics