This paper discusses topological and locally linear actions of finite groups on S4. Local linearity of the orientation preserving actions on S4 forces the group to be a subgroup of SO(5). On the other hand, orientation reversing topological actions of “exotic” groups G (i.e. G 6⊂ O(5)) on S4 are constructed, and local linearity and stable smoothability of the actions are studied.
Available at: http://works.bepress.com/weiminchen_chen/11/