WebMar 6, 2024 · The α -inaccessible cardinals can also be described as fixed points of functions which count the lower inaccessibles. For example, denote by ψ0 ( λ) the λth inaccessible cardinal, then the fixed points of ψ0 are the 1-inaccessible cardinals. The term "α-inaccessible cardinal" is ambiguous and different authors use inequivalent definitions. One definition is that a cardinal κ is called α-inaccessible, for α any ordinal, if κ is inaccessible and for every ordinal β < α, the set of β-inaccessibles less than κ is unbounded in κ (and thus of cardinality κ, since κ is … See more In set theory, an uncountable cardinal is inaccessible if it cannot be obtained from smaller cardinals by the usual operations of cardinal arithmetic. More precisely, a cardinal κ is strongly inaccessible if it is uncountable, it is not … See more • Worldly cardinal, a weaker notion • Mahlo cardinal, a stronger notion • Club set See more Zermelo–Fraenkel set theory with Choice (ZFC) implies that the $${\displaystyle \kappa }$$th level of the Von Neumann universe See more There are many important axioms in set theory which assert the existence of a proper class of cardinals which satisfy a predicate of interest. … See more • Drake, F. R. (1974), Set Theory: An Introduction to Large Cardinals, Studies in Logic and the Foundations of Mathematics, vol. 76, Elsevier Science, ISBN 0-444-10535-2 • Hausdorff, Felix (1908), "Grundzüge einer Theorie der geordneten Mengen" See more
Inaccessible cardinal - HandWiki
WebA Mahlo cardinal (or strongly Mahlo cardinal) is an inaccessible cardinal \ (\alpha\) such that the set of inaccessible cardinals below \ (\alpha\) is a stationary subset of \ (\alpha\) — that is, every closed unbounded set in \ (\alpha\) contains an inaccessible cardinal (in which the Von Neumann definition of ordinals is used). WebSep 19, 2024 · We will have to do the same for inaccessible cardinals. It’s really hard to get across just how unfathomable the size of an inaccessible cardinal is. I’ll just leave it at this: the conceptual jump from nothing to the … greeting to church members
Cardinal number - Encyclopedia of Mathematics
WebIn set theory, an uncountable cardinal is inaccessible if it cannot be obtained from smaller cardinals by the usual operations of cardinal arithmetic. More precisely, a cardinal κ is strongly inaccessible if it is uncountable, it is not a sum of fewer than κ cardinals smaller than κ, and α < κ {\displaystyle \alpha <\kappa } implies 2 α < κ {\displaystyle 2^{\alpha … WebJul 14, 2024 · 5. A Mahlo cardinal has to be regular, which ℵ ω is not. ℵ ω = ⋃ ℵ n, so cf ( ℵ ω) = ℵ 0. Every strong inaccessible κ satisfies κ = ℵ κ, but even that is not enough as the lowest κ satisfying that has cf ( κ) = ℵ 0. As we can't prove even that strong inaccessibles exist, we can't say where they are in the ℵ heirarchy ... WebJan 22, 2024 · An inaccessible cardinal is a cardinal number κ \kappa which cannot be “accessed” from smaller cardinals using only the basic operations on cardinals. It follows … greeting to customer in email