Laurent Mazet

Characterizations of Lojasiewicz inequalities: Subgradient flows, talweg, convexity

The classical Lojasiewicz inequality and its extensions for partial differential equation problems (Simon) and to o-minimal structures (Kurdyka) have a considerable impact on the analysis of gradient-like methods and related problems: minimization methods, complexity theory, asymptotic analysis of dissipative partial differential equations, tame geometry. This paper provides alternative characterizations of this type of inequalities for nonsmooth lower semicontinuous functions defined on a metric or a real Hilbert space. In a metric context, we show that a generalized form of the Lojasiewicz inequality (hereby called the Kurdyka-Lojasiewicz inequality) relates to metric regularity and to the Lipschitz continuity of the sublevel mapping, yielding applications to discrete methods (strong convergence of the proximal algorithm). In a Hilbert setting we further establish that asymptotic properties of the semiflow generated by

The Dirichlet problem for the minimal surface equation, with possible infinite boundary data, over domains in a Riemannian surface

-\partial f

Cylindrically bounded constant mean curvature surfaces in H 2 ×R

are strongly linked to this inequality. This is done by introducing the notion of a piecewise subgradient curve: such curves have uniformly bounded lengths if and only if the Kurdyka-Lojasiewicz inequality is satisfied. Further characterizations in terms of talweg lines -a concept linked to the location of the less steepest points at the level sets of

Optimal length estimates for stable CMC surfaces in 3-space forms

f

A quasi-periodic minimal surface

- and integrability conditions are given. In the convex case these results are significantly reinforced, allowing in particular to establish the asymptotic equivalence of discrete gradient methods and continuous gradient curves. On the other hand, a counterexample of a convex C^2 function in in the plane is constructed to illustrate the fact that, contrary to our intuition, and unless a specific growth condition is satisfied, convex functions may fail to fulfill the Kurdyka-Lojasiewicz inequality.

The plateau problem at infinity for horizontal ends and genus 1

In this paper, we study existence and uniqueness of solutions to Jenkins-Serrin type problems on domains in a Riemannian surface. In the case of unbounded domains, the study is focused on the hyperbolic plane.

On minimal spheres of area

In this paper we prove that a properly embedded constant mean curvature surface in

4\pi

\mathbb{H}^2\times\mathbb{R}

and rigidity

which has finite topology and stays at a finite distance from a vertical geodesic line is invariant by rotation around a vertical geodesic line.

Characterizations of Lojasiewicz inequalities: Subgradient ows, talweg, convexity

In this paper, we study stable constant mean curvature