Inter-universal geometry と ABC予想 (応援スレ) 55

Inter-universal geometry と ABC予想 (応援スレ) 55at MATH

Inter-universal geometry と ABC予想 (応援スレ) 55 - 暇つぶし2ch308:謔､な添字付けによって尽くされるならば、S は可賦番であるという。有向集合による添字付けは有向点族（ネット）の概念に用いられる。 https://en.wikipedia.org/wiki/Index_set In mathematics, an index set is a set whose members label (or index) members of another set.[1][2] For instance, if the elements of a set A may be indexed or labeled by means of the elements of a set J, then J is an index set. The indexing consists of a surjective function from J onto A, and the indexed collection is typically called an (indexed) family, often written as {Aj}j∈J. Contents 1 Examples 2 Other uses 3 See also Examples An enumeration of a set S gives an index set J⊂ N , where f : J → S is the particular enumeration of S. Any countably infinite set can be (injectively) indexed by the set of natural numbers N . For r∈ R, the indicator function on r is the function 1r： R → {0,1} given by 略 The set of all such indicator functions, {1r}r∈ R , is an uncountable set indexed by R . Other uses In computational complexity theory and cryptography, an index set is a set for which there exists an algorithm I that can sample the set efficiently; e.g., on input 1n, I can efficiently select a poly(n)-bit long element from the set.[3] (引用終り) 以上

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