István Györi

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This paper presents a generalization of the classical compartmental models using the concept of "pipes" between the compartments and taking into account the time needed for the material to pass through these pipes. A general linear delay differential system describing such models is derived and some properties of its solutions-such as nonnegativity,(More)
In this paper we give easily verifiable, but sharp (in most cases necessary and sufficient) algebraic conditions for the solutions of systems of higher order linear difference equations to be periodic. The main tool in our investigation is a transformation, recently introduced by the authors, which formulates a given higher order recursion as a first order(More)
In this paper we give a brief overview of the application of delay differential equations with piecewise constant arguments (EPCAs) for obtaining numerical approximation of delay differential equations, and we show that this method can be used for numerical approximation in a class of age-dependent population models. We also formulate an open problem for a(More)
In this paper we investigate the existence of nontrivial periodic solutions of a higher order system of difference equations. Our framework is based on an earlier periodicity condition of us. We also use the theory of circulant matrices combined by a theorem of Silvester on the computation the determinant of block matrices. An illustrative application is(More)