Extendability of the $B_2$-arrangement

Torsten Hoge, Shota Maehara, Sven Wiesner

Let $(\mathcal{A},m)$ be a free multiarrangement, and let $\mathcal{E}$ be an extension of $(\mathcal{A},m)$. It is well known that if $\mathcal{A}$ is the Coxeter arrangement of t…