We prove that while there are maps T4→ #3(S2× S2) of arbitrarily large
degree, there is no branched cover from the 4–torus to #3(S2× S2). More
generally, we obtain that, as long as a closed manifold N satisfies a suitable
cohomological condition, any π1–surjective branched cover Tn→ N is a
homeomorphism.
Received: 25 January 2011
Revised: 27 January 2012
Accepted: 2 February 2012
Published: 10 July 2012
Proposed: David Gabai
Seconded: Benson Farb, Ronald Fintushel