Rational K(pi,1) complements and ordinary K(pi,1) complements
Determine whether the complement of every complex hyperplane arrangement that is a rational K(pi,1) space is necessarily a K(pi,1) space.
References
Whether the converse holds is an open question; cf. *{2.8}.
\begin{Qst} If $\mathcal{C}(\A)$ is a rational $K(\pi,1)$ space, is $\mathcal{C}(\A)$ a $K(\pi,1)$ space? \end{Qst}
— Koszul Orlik--Solomon Algebras from Non-supersolvable Arrangements
(2609.03836 - Le et al., 3 Sep 2026) in Section 6, Questions; Question immediately following the discussion of rational K(pi,1) and K(pi,1) complements