A nonlinear ergodic theorem for an amenable semigroup of nonexpansive mappings in a Hilbert space
Wataru Takahashi · Proceedings of the American Mathematical Society · 1981
We prove a nonlinear ergodic theorem for noncommutative semigroups of nonexpansive mappings in a Hilbert space. Furthermore, we give a necessary and sufficient condition for a noncommutative semigroup to have a fixed point.