In this paper some results on the topology of the space of k-flats in Rn are proved, similar to the Borsuk-Ulam theorem on coverings of sphere. Some corollaries on common transversals for families of compact sets in Rn, and on measure partitions by hyperplanes, are deduced.

The aim of this paper is to compute a simplicial cohomology group of some specific digital images. Then we define ringand algebra structures of a digital cohomology with the cup product. Finally, we prove a special case of the Borsuk-Ulam theorem fordigital images.

We show that Fan’s 1952 lemma on labelled triangulations of the n-sphere with n + 1 labels is equivalent to the Borsuk–Ulam theorem. Moreover, unlike other Borsuk–Ulam equivalents, we show that this lemma directly implies Sperner’s Lemma, so this proof may be regarded as a combinatorial version of the fact that the Borsuk–Ulam theorem implies the Brouwer fixed-point theorem, or that the Lustern...

Contents 1. Introduction 2 2. Metric type 7 2.1. Type for metric spaces 8 2.2. The geometric puzzle 11 2.3. Pisier's argument 12 2.4. Unique obstructions to type 17 3. Metric cotype 19 4. Markov type and cotype 22 4.1. Lipschitz extension via Markov type and cotype 27 5. Markov convexity 29 6. Metric smoothness? 32 7. Bourgain's discretization problem 32 8. Nonlinear Dvoretzky theorems 33 8.1. ...

Problems dealing with non-linear mappings which preserve certain distances have been analysed by a number of authors during the last decade, cf. the bibliography. In this paper we shall solve the following problem, which has been raised by C. Alsina at the International Symposium on Functional Equations held in BielskoBiaÃla, Katowice and Kraków in August 1989: Describe all volume preserving ma...