The presentation conjecture for invariant rank-two parabolic arrangements

Let WW be a finite real reflection group, and let P\mathscr{P} be a collection of rank 22 parabolic subgroups of WW closed under conjugation. Set

W={Fix(G):GP}.\mathscr{W}=\{\operatorname{Fix}(G):G\in\mathscr{P}\}.

Define a Coxeter group WW' with the same generating set SS as WW, with relations determined by

m(s,t)={if s,tP,\m(s,t)otherwise,m'(s,t)=\begin{cases}\infty&\text{if }\langle s,t\rangle\in\mathscr{P},\m(s,t)&\text{otherwise},\end{cases}

and let φ:WW\varphi':W'\to W send ss to ss for every sSs\in S. The presentation conjecture. The fundamental group of the complement satisfies

π1(M(W))kerφ,\pi_1(\mathcal{M}(\mathscr{W}))\cong\ker\varphi',

and W\mathscr{W} is a K(π,1)K(\pi,1)-arrangement, where π=kerφ\pi=\ker\varphi'. This would give a presentation of the fundamental group for complements of invariant codimension-two subspace arrangements; the conjecture is presented as an open question following the known K(π,1)K(\pi,1) results for the relevant arrangements.

Sources & referencesView supporting material

Primary source

Hélène Barcelo, Christopher Severs and Jacob A. White, “k-Parabolic Subspace Arrangements”, arXiv:0909.0720 (2009).

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