Compact branch sets and injectivity of proper branched coverings

In this paper, we show that a proper continuous open discrete map from the open unit ball Bⁿ onto a domain in ⁿ with n≥5 is a homeomorphism whenever its branch set is compact. This answers Vuorinen's question affirmatively in every dimension n≥5. In dimension four, we also show that, under the additional assumption of quasiregularity, the map is a quasiconformal homeomorphism. Together with the three-dimensional theorem of Kauranen, Luisto and Tengvall, these results answer the quasiregular question posed as Problem~7.66 in the collections of Barth--Brannan--Hayman and Hayman--Lingham in every dimension n≥3.