On exposed semigroup homomorphisms.
On extending automorphisms of models of Peano Arithmetic
Continuing the earlier research in [10] we give some information on extending automorphisms of models of PA to end extensions and cofinal extensions.
On extension of the group operation over the Čech-Stone compactification
The convolution of ultrafilters of closed subsets of a normal topological group is considered as a substitute of the extension onto of the group operation. We find a subclass of ultrafilters for which this extension is well-defined and give some examples of pathologies. Next, for a given locally compact group and its dense subgroup , we construct subsets of β algebraically isomorphic to . Finally, we check whether the natural mapping from β onto β is a homomorphism with respect to the extension...
On extension properties for observables
On extensions of Nelson's logic satisfying Dummett's axiom.
On External Properties of Nonstandard Models of Arithmetic
On extremum-searching approximate probabilistic algorithms
On families of Lindelöf and related subspaces of
We consider the families of all subspaces of size ω₁ of (or of a compact zero-dimensional space X of weight ω₁ in general) which are normal, have the Lindelöf property or are closed under limits of convergent ω₁-sequences. Various relations among these families modulo the club filter in are shown to be consistently possible. One of the main tools is dealing with a subspace of the form X ∩ M for an elementary submodel M of size ω₁. Various results with this flavor are obtained. Another tool used...
On families of σ-complete ideals
On fields and ideals connected with notions of forcing
We investigate an algebraic notion of decidability which allows a uniform investigation of a large class of notions of forcing. Among other things, we show how to build σ-fields of sets connected with Laver and Miller notions of forcing and we show that these σ-fields are closed under the Suslin operation.
On ...-filtered vector spaces and their application to abelian p-groups: I.
On fixed edges of antitone self-mappings of complete lattices.
On four intuitionistic fuzzy topological operators.
Four new operators, which are analogous of the topological operators interior and closure, are defined. Some of their basic properties are studied. Their geometrical interpretations are given.
On free Boolean vectors.
On free constructions.
On free -algebras
In the present paper we show that free -algebras can be constructed by applying free abelian lattice ordered groups.
On free modes
We prove a theorem describing the equational theory of all modes of a fixed type. We use this result to show that a free mode with at least one basic operation of arity at least three, over a set of cardinality at least two, does not satisfy identities selected by ’A. Szendrei in Identities satisfied by convex linear forms, Algebra Universalis 12 (1981), 103–122, that hold in any subreduct of a semimodule over a commutative semiring. This gives a negative answer to the question raised by A. Romanowska:...
On free pseudo-complemented and relatively pseudo-complemented semi-lattices
On FU()-spaces and -sequential spaces
Following Kombarov we say that is -sequential, for , if for every non-closed subset of there is such that and . This suggests the following definition due to Comfort and Savchenko, independently: is a FU()-space if for every and every there is a function such that . It is not hard to see that ( denotes the Rudin–Keisler order) every -sequential space is -sequential every FU()-space is a FU()-space. We generalize the spaces to construct examples of -sequential...
On Fuchs' problem 76.