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On absolute retracts of ω*

A. Bella, A. Błaszczyk, A. Szymański (1994)

Fundamenta Mathematicae

An extremally disconnected space is called an absolute retract in the class of all extremally disconnected spaces if it is a retract of any extremally disconnected compact space in which it can be embedded. The Gleason spaces over dyadic spaces have this property. The main result of this paper says that if a space X of π-weight ω 1 is an absolute retract in the class of all extremally disconnected compact spaces and X is homogeneous with respect to π-weight (i.e. all non-empty open sets have the same...

On CCC boolean algebras and partial orders

András Hajnal, István Juhász, Zoltán Szentmiklóssy (1997)

Commentationes Mathematicae Universitatis Carolinae

We partially strengthen a result of Shelah from [Sh] by proving that if κ = κ ω and P is a CCC partial order with e.g. | P | κ + ω (the ω th successor of κ ) and | P | 2 κ then P is κ -linked.

On minimal spectrum of multiplication lattice modules

Sachin Ballal, Vilas Kharat (2019)

Mathematica Bohemica

We study the minimal prime elements of multiplication lattice module M over a C -lattice L . Moreover, we topologize the spectrum π ( M ) of minimal prime elements of M and study several properties of it. The compactness of π ( M ) is characterized in several ways. Also, we investigate the interplay between the topological properties of π ( M ) and algebraic properties of M .

On the injectivity of Boolean algebras

Bernhard Banaschewski (1993)

Commentationes Mathematicae Universitatis Carolinae

The functor taking global elements of Boolean algebras in the topos 𝐒𝐡 𝔅 of sheaves on a complete Boolean algebra 𝔅 is shown to preserve and reflect injectivity as well as completeness. This is then used to derive a result of Bell on the Boolean Ultrafilter Theorem in 𝔅 -valued set theory and to prove that (i) the category of complete Boolean algebras and complete homomorphisms has no non-trivial injectives, and (ii) the category of frames has no absolute retracts.

Partitions of k -branching trees and the reaping number of Boolean algebras

Claude Laflamme (1993)

Commentationes Mathematicae Universitatis Carolinae

The reaping number 𝔯 m , n ( 𝔹 ) of a Boolean algebra 𝔹 is defined as the minimum size of a subset 𝒜 𝔹 { 𝐎 } such that for each m -partition 𝒫 of unity, some member of 𝒜 meets less than n elements of 𝒫 . We show that for each 𝔹 , 𝔯 m , n ( 𝔹 ) = 𝔯 m n - 1 , 2 ( 𝔹 ) as conjectured by Dow, Steprāns and Watson. The proof relies on a partition theorem for finite trees; namely that every k -branching tree whose maximal nodes are coloured with colours contains an m -branching subtree using at most n colours if and only if n < k m - 1 .

Representation of a Boolean algebra by its triangular norms.

Suryansu Ray (1997)

Mathware and Soft Computing

Given a complete and atomic Boolean algebra B, there exists a family taugamma of triangular norms on B such that, under the partial ordering of triangular norms, taugamma is a Boolean algebra isomorphic to B, where gamma is the set of all atoms in B. In other words, as we have shown in this note, every complete and atomic Boolean algebra can be represented by its own triangular norms. What we have not shown in this paper is our belief that taugamma is not unique for B and that, for such a representation,...

Some properties of Eulerian lattices

R. Subbarayan, A. Vethamanickam (2014)

Commentationes Mathematicae Universitatis Carolinae

In this paper, we prove that Eulerian lattices satisfying some weaker conditions for lattices or some weaker conditions for 0-distributive lattices become Boolean.

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