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In mathematics, a separoid is a binary relation between disjoint sets which is stable as an ideal in the canonical order induced by inclusion. Many mathematical objects which appear to be quite different, find a common generalisation in the framework of separoids; e.g., graphs, configurations of convex sets, oriented matroids, and polytopes. Any countable category is an induced subcategory of separoids when they are endowed with homomorphisms () (viz., mappings that preserve the so-called ''minimal Radon partitions''). In this general framework, some results and invariants of different categories turn out to be special cases of the same aspect; e.g., the pseudoachromatic number from graph theory and the Tverberg theorem from combinatorial convexity are simply two faces of the same aspect, namely, complete colouring of separoids. == The axioms == A separoid () is a set endowed with a binary relation on its power set, which satisfies the following simple properties for : : : : A related pair is called a separation and we often say that ''A is separated from B''. It is enough to know the ''maximal'' separations to reconstruct the separoid. A mapping is a morphism of separoids if the preimages of separations are separations; that is, for : 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Separoid」の詳細全文を読む スポンサード リンク
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