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This chapter contains an introduction to triangle comparison theorems and it is proved that the fundamental group of a compact Riemannian manifold with negative sectional curvature is hyperbolic. ...
We study conditions under which a point of a Riemannian surface has a neighborhood that can be parametrized by polar coordinates. The point under investigation can be a regular point or a conical singularity. We also study the regularity of these polar coo ...
In this article, we study the problem (sometimes called the Berger-Nirenberg problem) of prescribing the curvature on a Riemann surface (that is on an oriented surface equipped with a conformal class of Riemannian metrics). ...
We study sequences of metrics on a compact surface with bounded area and curvature and I prove that if the conformalstructure of these metrics remains bounded, then either the sequence contains a convergent subsequence, or there exists a point at which a c ...
In this paper, we prove that if f is a conformal map between two Riemannian surfaces, and if the curvature of the target is nonpositive and less than or equal to the curvature of the source, then the map is contracting. ...
Using methods based on (complex) projective geometry we give a classification of all metrics with constant curvature on a sphere with two conical singularities. ...
