We say that a group G is ultrahopfian if every homomorphism from G to G, with image H normal in G and G/H abelian, is an automorphism. In this paper, we prove that certain surface mapping class groups are ultrahopfian. Z ‹‰ .
This paper is to appear in the Mathematical Proceedings of the Cambridge Philosophical Society.
Contact: mccarthy@math.msu.edu
Last Revised 7/9/99