## Abstract For any Boolean Algebra __A__, let c~mm~(__A__) be the smallest size of an infinite partition of unity in __A.__ The relationship of this function to the 21 common functions described in Monk [4] is described, for the class of all Boolean algebras, and also for its most important subcla
Odd-sized partitions of Russell-sets
โ Scribed by Horst Herrlich; Eleftherios Tachtsis
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 113 KB
- Volume
- 56
- Category
- Article
- ISSN
- 0044-3050
No coin nor oath required. For personal study only.
โฆ Synopsis
In the setting of ZF, i.e., Zermelo-Fraenkel set theory without the Axiom of Choice (AC), we study partitions of Russell-sets into sets each with exactly n elements (called n-ary partitions), for some integer n. We show that if n is odd, then a Russell-set X has an n-ary partition if and only if |X| is divisible by n. Furthermore, we establish that it is relative consistent with ZF that there exists a Russell-set X such that |X| is not divisible by any finite cardinal n > 1.
๐ SIMILAR VOLUMES
We prove a lemma that is useful for obtaining upper bounds for the number of partitions without a given subsum. From this we can deduce an improved upper bound for the number of sets represented by the (unrestricted or into unequal parts) partitions of an integer n.
Given 3n points in the unit square, n >12, they determine n triangles whose vertices exhaust the given 3n points in many ways. Choose the n triangles so that the sum of their areas is minimal, and let a\*(n) be the maximum value of this minimum over all configurations of 3n points. Then n-~<< a\*(n)
Given a graph G, its odd set is a set of all integers k such that G has odd number of vertices of degree k. We show that if two graphs G and H of the same order have the same odd sets then they can be obtained from each other by succesive application of the following two operations: โข add or remove