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A sufficient condition of full normality

Tomáš Kaiser (1996)

Commentationes Mathematicae Universitatis Carolinae

We present a direct constructive proof of full normality for a class of spaces (locales) that includes, among others, all metrizable ones.

A survey of hereditary properties of graphs

Mieczysław Borowiecki, Izak Broere, Marietjie Frick, Peter Mihók, Gabriel Semanišin (1997)

Discussiones Mathematicae Graph Theory

In this paper we survey results and open problems on the structure of additive and hereditary properties of graphs. The important role of vertex partition problems, in particular the existence of uniquely partitionable graphs and reducible properties of graphs in this structure is emphasized. Many related topics, including questions on the complexity of related problems, are investigated.

A topological duality for the F -chains associated with the logic C ω

Verónica Quiroga, Víctor Fernández (2017)

Mathematica Bohemica

In this paper we present a topological duality for a certain subclass of the F ω -structures defined by M. M. Fidel, which conform to a non-standard semantics for the paraconsistent N. C. A. da Costa logic C ω . Actually, the duality introduced here is focused on F ω -structures whose supports are chains. For our purposes, we characterize every F ω -chain by means of a new structure that we will call down-covered chain (DCC) here. This characterization will allow us to prove the dual equivalence between the...

A topological view of ordered groups

Dale Rolfsen (2014)

Banach Center Publications

In this expository article we use topological ideas, notably compactness, to establish certain basic properties of orderable groups. Many of the properties we shall discuss are well-known, but I believe some of the proofs are new. These will be used, in turn, to prove some orderability results, including the left-orderability of the group of PL homeomorphisms of a surface with boundary, which are fixed on at least one boundary component.

A visual approach to test lattices

Gábor Czédli (2009)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

Let p be a k -ary lattice term. A k -pointed lattice L = ( L ; ∨ , ∧ , d 1 , ... , d k ) will be called a p -lattice (or a test lattice if p is not specified), if ( L ; ∨ , ∧ ) is generated by { d 1 , ... , d k } and, in addition, for any k -ary lattice term q satisfying p ( d 1 , ... , d k ) ≤ q ( d 1 , ... , d k ) in L , the lattice identity p ≤ q holds in all lattices. In an elementary visual way, we construct a finite p -lattice L ( p ) for each p . If p is a canonical lattice term,...

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