We study the closures of classes of log-concave measures under taking weak limits, linear transformations and tensor products. We investigate which uniform measures on convex bodies can be obtained starting from some class 𝒦. In particular we prove that if one starts from one-dimensional log-concave measures, one obtains no non-trivial uniform mesures on convex bodies.
We construct a Lipschitz function on which is locally convex on the complement of some totally disconnected compact set but not convex. Existence of such function disproves a theorem that appeared in a paper by L. Pasqualini and was also cited by other authors.
We study various aspects of nonexpansive retracts and retractions in certain Banach and metric spaces, with special emphasis on the compact nonexpansive envelope property.
We collect several variants of the proof of the third case of the Bessaga-Klee relative classification of closed convex bodies in topological vector spaces. We were motivated by the fact that we have not found anywhere in the literature a complete correct proof. In particular, we point out an error in the proof given in the book of C. Bessaga and A. Pełczyński (1975). We further provide a simplified version of T. Dobrowolski's proof of the smooth classification of smooth convex bodies in Banach...
V tomto článku představíme jeden méně známý elegantní důkaz Pickova vzorce pro výpočet obsahu jednoduchých mřížových mnohoúhelníků, který je založen na tzv. úhlech viditelnosti. Princip tohoto důkazu lze částečně použít i k odvození zobecněného Pickova vzorce pro mřížové mnohoúhelníky, které nejsou jednoduché. Dále naznačíme potíže spojené s prostorovou analogií Pickova vzorce. Nakonec ukážeme, jak Pickův vzorec souvisí s rozměňováním peněz.