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Displaying 61 – 80 of 92

Weil uniformities for frames

Jorge Picado (1995)

Commentationes Mathematicae Universitatis Carolinae

In pointfree topology, the notion of uniformity in the form of a system of covers was introduced by J. Isbell in [11], and later developed by A. Pultr in [14] and [15]. Another equivalent notion of locale uniformity was given by P. Fletcher and W. Hunsaker in [6], which they called “entourage uniformity”. The purpose of this paper is to formulate and investigate an alternative definition of entourage uniformity which is more likely to the Weil pointed entourage uniformity, since it is expressed...

Well posedness for evolution inclusions.

Balachandran, K., Anguraj, A. (1994)

Journal of Applied Mathematics and Stochastic Analysis

Well-chainedness and connectedness.

Pataki, G., Száz, Á. (2003)

Acta Mathematica Academiae Paedagogicae Nyí regyháziensis. New Series [electronic only]

Wellchainedness characterizations of connected relators.

Kurdics, János, Száz, Árpád (1993)

Mathematica Pannonica

Well-posed minimum problems for preorders

Fioravante Patrone (1990)

Rendiconti del Seminario Matematico della Università di Padova

Well-posedness and fractals via fixed point theory.

Chifu, Cristian, Petruşel, Gabriela (2008)

Fixed Point Theory and Applications [electronic only]

Weyl almost periodic points in topological dynamics

Anzelm Iwanik (1988)

Colloquium Mathematicum

What should be a rate of convergence ?

Vlastimil Pták (1977)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

What to embed into a Cartesian closed topological category (Preliminary communication)

Jiří Adámek, Václav Koubek (1977)

Commentationes Mathematicae Universitatis Carolinae

When a composition algebra is barrelled?

Jorge Bustamante González, Raúl Escobedo Conde (1997)

Extracta Mathematicae

When are Borel functions Baire functions?

M. Fosgerau (1993)

Fundamenta Mathematicae

The following two theorems give the flavour of what will be proved. Theorem. Let Y be a complete metric space. Then the families of first Baire class functions and of first Borel class functions from [0,1] to Y coincide if and only if Y is connected and locally connected.Theorem. Let Y be a separable metric space. Then the families of second Baire class functions and of second Borel class functions from [0,1] to Y coincide if and only if for all finite sequences $U_{1}, . . ., U_{q}$ of nonempty open subsets of Y there...

When $C_{p} (X)$ is domain representable

William Fleissner, Lynne Yengulalp (2013)

Fundamenta Mathematicae

Let M be a metrizable group. Let G be a dense subgroup of $M^{X}$ . We prove that if G is domain representable, then $G = M^{X}$ . The following corollaries answer open questions. If X is completely regular and $C_{p} (X)$ is domain representable, then X is discrete. If X is zero-dimensional, T₂, and $C_{p} (X,)$ is subcompact, then X is discrete.

When categories of presheaves are binding

Trnková, V., Reiterman, J. (1972)

General Topology and its Relations to Modern Analysis and Algebra

When every point is either transitive or periodic

Tomasz Downarowicz, Xiangdong Ye (2002)

Colloquium Mathematicae

We study transitive non-minimal ℕ-actions and ℤ-actions. We show that there are such actions whose non-transitive points are periodic and whose topological entropy is positive. It turns out that such actions can be obtained by perturbing minimal systems under some reasonable assumptions.

When finely continuous functions are of the first class of Baire

Jaroslav Lukeš, Luděk Zajíček (1977)

Commentationes Mathematicae Universitatis Carolinae

When is a group homomorphism a covering homomorphism?

J. C. Santos (2007)

Extracta Mathematicae

When is any continuous function Lipschitzian?

Giuseppe Marino (1998)

Extracta Mathematicae

When is $𝐍$ Lindelöf?

Horst Herrlich, George E. Strecker (1997)

Commentationes Mathematicae Universitatis Carolinae

Theorem. In ZF (i.e., Zermelo-Fraenkel set theory without the axiom of choice) the following conditions are equivalent: (1) $ℕ$ is a Lindelöf space, (2) $ℚ$ is a Lindelöf space, (3) $ℝ$ is a Lindelöf space, (4) every topological space with a countable base is a Lindelöf space, (5) every subspace of $ℝ$ is separable, (6) in $ℝ$ , a point $x$ is in the closure of a set $A$ iff there exists a sequence in $A$ that converges to $x$ , (7) a function $f : ℝ \to ℝ$ is continuous at a point $x$ iff $f$ is sequentially continuous at $x$ , (8)...

When must a base for a locally connected space contain a base of connected sets?

Foland, N., Nevin, B., Pedersen, F. (1977)

Portugaliae mathematica

When spectra of lattices of $z$ -ideals are Stone-Čech compactifications

Themba Dube (2017)

Mathematica Bohemica

Let $X$ be a completely regular Hausdorff space and, as usual, let $C (X)$ denote the ring of real-valued continuous functions on $X$ . The lattice of $z$ -ideals of $C (X)$ has been shown by Martínez and Zenk (2005) to be a frame. We show that the spectrum of this lattice is (homeomorphic to) $β X$ precisely when $X$ is a $P$ -space. This we actually show to be true not only in spaces, but in locales as well. Recall that an ideal of a commutative ring is called a $d$ -ideal if whenever two elements have the same annihilator and...

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