Kw. Zhang, ON CONNECTED SUBSETS OF M(2X2) WITHOUT RANK-ONE CONNECTIONS, Proceedings of the Royal Society of Edinburgh. Section A. Mathematics, 127, 1997, pp. 207-216
We prove that connected subsets of M(2x2) without rank-one connections
are Lipschitz graphs of mappings from subsets of a fixed two-dimensio
nal subspace to its orthogonal complement. Under a weaker condition th
at the set does not have rank-one connections locally, we are able to
establish some global results on the set. We also establish some resul
ts on Lipschitz extensions of the functions thus obtained.