Papadima–Suciu conjecture on prime-power monodromy orders

Let ${\mathcal A}$ be a real arrangement, let $F$ be its Milnor fiber, and let monodromy mean the action induced on the homology of $F$. A nontrivial monodromy has prime-power order when its order is a power of a prime. Papadima–Suciu's conjecture. The only possible nontrivial monodromies of prime-power order have order $3$ or $4$. This conjecture addresses the possible orders of nontrivial monodromy in arrangement Milnor fibers; its status is open in the supplied source.