Conformality, classical and generalized

We discuss several topics: the concept of conformal mapping of Riemannian and pseudo-Riemannian manifolds, conformal rigidity of higher-dimensional domains, and conformal flexibility of two-dimensional domains of Euclidian and Minkowski planes. We present an extension of the concept of conformal mapping proposed by M. Gromov and recall an open problem related to it.

Three-dimensional connected groups of automorphisms of toroidal circle planes

We contribute to the classification of toroidal circle planes and flat Minkowski planes possessing three-dimensional connected groups of automorphisms. When such a group is an almost simple Lie group, we show that it is isomorphic to PSL(2, ℝ). Using this result, we describe a framework for the full classification based on the action of the group on the point set.

On the Erdős-Mordell inequality for normed planes and spaces

In the Euclidean plane, the Erdős-Mordell inequality indicates that the sum of distances of an interior point of a triangle T to its vertices is larger than or equal to twice the sum of distances to the sides of T. We extend this theorem to arbitrary (normed or) Minkowski planes, and we generalize in an analogous way some other related inequalities, e.g. referring to polygons. We also derive Minkowskian analogues of Erdős-Mordell inequalities for tetrahedra and n-dimensional simplices. Finally, some related inequalities are obtained which additionally involve total edge-lengths of simplices.

Modified classical flat Minkowski planes

We construct anew family of flat Minkowski planes that admit the simple group PSL