147–148) about whether finite subgroups of mapping class groups can act on surfaces, that was answered positively by Steven Kerckhoff (1980, 1983).
An equivalent way of stating the question asks whether every finite subgroup of the mapping class group fixes some point of Teichmüller space.
147–148) asked whether finite subgroups of mapping class groups can act on surfaces.
Linch (1971) pointed out a gap in the argument, and Masur (1975) showed that Teichmüller space is not negatively curved.
Steven Kerckhoff (1980, 1983) gave a correct proof that finite subgroups of mapping class groups can act on surfaces using left earthquakes.