hadamard (or complete $cat(0)$) spaces are complete, non-positive curvature, metric spaces. here,
we prove a nonlinear ergodic theorem for continuous non-expansive semigroup in these spaces as well as a strong convergence theorem for
the commutative case. our results extend the standard non-linear
ergodic theorems for non-expansive maps on real hilbert spaces,
to non-expansive maps on had...
