Homomorphisms From Mapping Class Groups
Department of Mathematics, King's College London WC2R 2LS, United Kingdom bill.harvey{at}kcl.ac.uk
Department of Mathematics, Middle East Technical University 06531 Ankara, Turkey korkmaz{at}arf.math.metu.edu.tr
Received 2 June 2003. Revision received 16 February 2004.
This paper concerns rigidity of the mapping class groups. It is shown that any homomorphism
: Modg
Modh between mapping class groups of closed orientable surfaces with distinct genera g > h is trivial if g
3, and has finite cyclic image for all g
1.
Some implications are drawn for more general homomorphs of these groups. 2000 Mathematics Subject Classification 57N05 (primary), 20E25, 30F10 (secondary).
The second author was supported in part by the Turkish Academy of Sciences, under the Young Scientists Award Programme (MK/TÜBA-GEB
P 200310).