منابع مشابه
On Set Systems Having Paradoxical Covering Properties
1. R2-phenomena . Our set theoretic notation will be standard with one exception . Since this paper is largely concerned with powers of ordinals, the symbol ~" will always denote ordinal exponentiation for ordinals ~, 11 . Thus, in particular, if fl--a, then cos is an ordinal <coy+1 . When we use cardinal exponentiation we shall either say so or, if there is no danger of confusion, we write 2 1...
متن کاملCovering properties of ideals
M. Elekes proved that any infinite-fold cover of a σ-finite measure space by a sequence of measurable sets has a subsequence with the same property such that the set of indices of this subsequence has density zero. Thanks to this theorem he gave a new proof for the random-indestructibility of the density zero ideal. He asked about other variants of this theorem. We present some negative results...
متن کاملAdditivity Numbers of Covering Properties
The additivity number of a topological property (relative to a given space) is the minimal number of subspaces with this property whose union does not have the property. The most well-known case is where this number is greater than א0, i.e. the property is σ-additive. We give a rather complete survey of the known results about the additivity numbers of a variety of topological covering properti...
متن کاملUniformities and covering properties for partial frames (I)
Partial frames provide a rich context in which to do pointfree structured and unstructured topology. A small collection of axioms of an elementary nature allows one to do much traditional pointfree topology, both on the level of frames or locales, and that of uniform or metric frames. These axioms are sufficiently general to include as examples bounded distributive...
متن کاملOn δ-continuous selections of small multifunctions and covering properties
The spaces for which each δ-continuous function can be extended to a 2δ-small point-open l.s.c. multifunction (resp. point-closed u.s.c. multifunction) are studied. Some sufficient conditions and counterexamples are given.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Mathematische Nachrichten
سال: 1989
ISSN: 0025-584X,1522-2616
DOI: 10.1002/mana.19891410106