11,505 research outputs found
Oort groups and lifting problems
Let k be an algebraically closed field of positive characteristic p. We
consider which finite groups G have the property that every faithful action of
G on a connected smooth projective curve over k lifts to characteristic zero.
Oort conjectured that cyclic groups have this property. We show that if a
cyclic-by-p group G has this property, then G must be either cyclic or
dihedral, with the exception of A_4 in characteristic 2. This proves one
direction of a strong form of the Oort Conjecture.Comment: 20 page
- …