In this paper a particular case of z-ideals, called strongly z-ideal, is defined by introducing zero sets in pointfree topology. We study strongly z-ideals, their relation with z-ideals and the role of spatiality in this relation. For strongly z-ideals, we analyze prime ideals using the concept of zero sets. Moreover, it is proven that the intersection of all zero sets of a prime ideal of C(L),...

0-efficient triangulations of 3-manifolds are defined and studied. It is shown that any triangulation of a closed, orientable, irreducible 3-manifold M can be modified to a 0-efficient triangulation orM can be shown to be one of the manifolds S3,RP3 or L(3, 1). Similarly, any triangulation of a compact, orientable, irreducible, ∂-irreducible 3-manifold can be modified to a 0-efficient triangula...

A non-empty subset of a topological space is irreducible if whenever it is covered by the union of two closed sets, then already it is covered by one of them. Irreducible sets occur in proliferation: (1) every singleton set is irreducible, (2) directed subsets (which of fundamental status in domain theory) of a poset are exactly its Alexandroff irreducible sets, (3) directed subsets (with respe...

A strongly Fregean algebra is an such that the class of its homomorphic images and variety generated by this congruence modular. To understand structure these algebras we study prime intervals projectivity relation in posets their completely meet irreducible congruences show cosets have natural a Boolean group. In particular, approach allows us to represent elements as subsets upward closed wit...

In this paper we introduce the notion of intuitionistic fuzzy prime, strongly prime, semiprime bi-ideals in ternary semigroup and look for some of their related characteristics. Also here we introduce irreducible and strongly irreducible intuitionistic fuzzy bi-ideals in a ternary semigroup. AMS subject classification: 20N10, 20M12, 04A72.

Clifford theory of finite groups is generalized to association schemes. It shows a relation between irreducible complex characters of a scheme and a strongly normal closed subset of the scheme. The restriction of an irreducible character of a scheme to a strongly normal closed subset coniatns conjugate characters with same multiplicities. Moreover some strong relations are obtained.

We prove that the associated variety of a Poisson prime ideal of the centre of a symplectic reflection algebra at parameter t = 0 is irreducible.

We generalize Freudenthal’s theory of irreducible representations of metrizable compacta by inverse sequences of compact polyhedra to the class of all metrizable spaces. Our representations consist of inverse sequences of completely metrizable polyhedra which are ANR’s. They are extendable: any such representation of a closed subspace of a given metrizable space extends to another such of the e...

We show that under reasonable conditions, the spines of the handlebodies of a strongly irreducible Heegaard splitting will intersect a closed ball in a graph which is isotopic into the boundary of the ball. This is in some sense a generalization of the results by Scharlemann on how a strongly irreducible Heegaard splitting surface can intersect a ball. AMS Classification 57M27; 57Q10

In [Topology Appl. 90 (1998) 135] Scharleman showed that a strongly irreducible Heegaard splitting surface Q of a 3-manifold M can, under reasonable side conditions, intersect a ball or a solid torus in M in only a few possible ways. Here we extend those results to describe how Q can intersect a handlebody inM .  2001 Elsevier Science B.V. All rights reserved.