Gradient flows and diffusion semigroups in metric spaces under lower curvature bounds

We present some new results concerning well-posedness of gradient flows generated by lambda-convex functionals in a wide class of metric spaces, including Alexandrov spaces satisfying a lower curvature bound and the corresponding L-2-Wasserstein spaces. Applications to the gradient flow of Entropy functionals in metric-measure spaces with Ricci curvature bounded from below and to the corresponding diffusion semigroup are also considered. These results have been announced during the workshop on Optimal Transport: theory and applications held in Pisa, November 2006.