On the third homotopy group of Orr's space
arXiv:1703.10537 · doi:10.2140/agt.2018.18.569
Abstract
K. Orr defined a Milnor-type invariant of links that lies in the third homotopy group of a certain space The problem of non-triviality of this third homotopy group has been open. We show that it is an infinitely generated group. The question of realization of its elements as links remains open.