All a b c d e f g h i j k l m n o p q r s t u v w x y z Other

Previous Page 46 Next

Displaying 901 – 920 of 8496

Showing per page

Almost disjoint families and “never” cardinal invariants

Charles Morgan, Samuel Gomes da Silva (2009)

Commentationes Mathematicae Universitatis Carolinae

We define two cardinal invariants of the continuum which arise naturally from combinatorially and topologically appealing properties of almost disjoint families of sets of the natural numbers. These are the never soft and never countably paracompact numbers. We show that these cardinals must both be equal to ω 1 under the effective weak diamond principle ♦ ( ω , ω , < ) , answering questions of da Silva S.G., On the presence of countable paracompactness, normality and property ( a ) in spaces from almost disjoint families,...

Almost disjoint families and property (a)

Paul Szeptycki, Jerry Vaughan (1998)

Fundamenta Mathematicae

We consider the question: when does a Ψ-space satisfy property (a)? We show that if | A | < p then the Ψ-space Ψ(A) satisfies property (a), but in some Cohen models the negation of CH holds and every uncountable Ψ-space fails to satisfy property (a). We also show that in a model of Fleissner and Miller there exists a Ψ-space of cardinality p which has property (a). We extend a theorem of Matveev relating the existence of certain closed discrete subsets with the failure of property (a).

Almost g ˜ α -closed functions and separation axioms

O. Ravi, S. Ganesan, R. Latha (2012)

Mathematica Bohemica

We introduce a new class of functions called almost g ˜ α -closed and use the functions to improve several preservation theorems of normality and regularity and also their generalizations. The main result of the paper is that normality and weak normality are preserved under almost g ˜ α -closed continuous surjections.

Almost locatedness in uniform spaces

Douglas Bridges, Hajime Ishihara, Ray Mines, Fred Richman, Peter Schuster, Luminiţa Vîţă (2007)

Czechoslovak Mathematical Journal

A weak form of the constructively important notion of locatedness is lifted from the context of a metric space to that of a uniform space. Certain fundamental results about almost located and totally bounded sets are then proved.

Almost maximal topologies on groups

Yevhen Zelenyuk (2016)

Fundamenta Mathematicae

Let G be a countably infinite group. We show that for every finite absolute coretract S, there is a regular left invariant topology on G whose ultrafilter semigroup is isomorphic to S. As consequences we prove that (1) there is a right maximal idempotent in βG∖G which is not strongly right maximal, and (2) for each combination of the properties of being extremally disconnected, irresolvable, and nodec, except for the combination (-,-,+), there is a corresponding regular almost maximal left invariant...

Almost orthogonality and Hausdorff interval topologies of atomic lattice effect algebras

Jan Paseka, Zdena Riečanová, Junde Wu (2010)

Kybernetika

We prove that the interval topology of an Archimedean atomic lattice effect algebra E is Hausdorff whenever the set of all atoms of E is almost orthogonal. In such a case E is order continuous. If moreover E is complete then order convergence of nets of elements of E is topological and hence it coincides with convergence in the order topology and this topology is compact Hausdorff compatible with a uniformity induced by a separating function family on E corresponding to compact and cocompact elements....

Almost * realcompactness

John J. Schommer, Mary Anne Swardson (2001)

Commentationes Mathematicae Universitatis Carolinae

We provide a new generalization of realcompactness based on ultrafilters of cozero sets and contrast it with almost realcompactness.

Currently displaying 901 – 920 of 8496