Factorisation of Lefschetz zeta functions and twisted periodic orbits.
We prove that for each integer there is an open neighborhood of the identity map of the 2-sphere , in topology such that: if is a nilpotent subgroup of with length of nilpotency, generated by elements in , then the natural -action on has nonempty fixed point set. Moreover, the -action has at least two fixed points if the action has a finite nontrivial orbit.