Oldřich Kowalski, Zdeněk Vlášek (1999)
Mathematica Bohemica
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The first author and F. Prufer gave an explicit classification of all Riemannian 3-manifolds with distinct constant Ricci eigenvalues and satisfying additional geometrical conditions. The aim of the present paper is to get the same classification under weaker geometrical conditions.
Ján Jakubík (1997)
Mathematica Bohemica
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In this paper we generalize a result of V. N. Salij concerning direct product decompositions of lattices which are complete and uniquely complemented.
Eva Dontová, Miroslav Dont, Josef Král (1997)
Mathematica Bohemica
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A mixed boundary value problem on a doubly connected domain in the complex plane is investigated. The solution is given in an integral form using reflection mapping. The reflection mapping makes it possible to reduce the problem to an integral equation considered only on a part of the boundary of the domain.
Ondřej Došlý, Roman Hilscher (1997)
Mathematica Bohemica
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Necessary and sufficient conditions for discreteness and boundedness below of the spectrum of the singular differential operator , are established. These conditions are based on a recently proved relationship between spectral properties of and oscillation of a certain associated second order differential equation.
Jan Ligęza, Milan Tvrdý (1999)
Mathematica Bohemica
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From the fact that the unique solution of a homogeneous linear algebraic system is the trivial one we can obtain the existence of a solution of the nonhomogeneous system. Coefficients of the systems considered are elements of the Colombeau algebra of generalized real numbers. It is worth mentioning that the algebra is not a field.
Ján Jakubík (1998)
Mathematica Bohemica
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In the present paper we deal with the relations between direct product decompositions of a directed set and direct product decompositions of intervals of .