Le Matematiche (Dipartimento di Matematica e Informatica, Università degli Studi di Catania)
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A kinetic type extended model for dense gases and macromolecular fluids
Get PDFExtended thermodynamics is an important theory which is appreciated from mathematicians and physicists. Following its ideas and considering the macroscopic approach with suggestions from the kinetic one, we find in this paper, the solution of an interesting model: the model for dense gases and macromolecular fluids
Processi di controllo con parametri distribuiti in insiemi non limitati. Controllabilità con luogo iniziale variabile
Get PDFWe study the controllability with variable initial locus of some distributed parameter linear control system.In this setting, we study the controllability of such system from a given initial state, to be attained on the variable initial locus, to an arbitrary final state, to be attained on the fixed final locus l(a, b).We consider both exact and approximate controllability. We get a characterization of the approximate controllability when the set of the available controls is the unit ball of L^q (L I, J , Rm ), q ≥ p. Also, assuming a suitable invertibility property for the matrix F , we show a necessary and sufficient condition for the exact controllability when a larger set of available controls is considered. Finally, we study the permanence of both controllability properties with respect to changes of the fixed final locus l(a, b)
No geometric approach for general overdetermined elliptic problems with nonconstant source
Get PDFWe discuss the geometric approach developed in [8] for the study of overdetermined boundary value problems for general elliptic operators.We show that this approach does not apply when nonconstant sources are involved
Existence results for a class of non-uniformly elliptic equations
Get PDFWe present existence results for a class of non-uniformly elliptic problems.[omissis
Blocking sets and colouring in Steiner systems S(2,4,ν)
Get PDFA Steiner system S(2, 4, v) is a v-element set V together with a collection B of 4-subsets of V called blocks such that every 2-subset of V is contained in exactly one block
Connected graphs of fixed order and size with maximal index: structural considerations
Get PDFThe largest eigenvalue, or index, of simple graphs is extensively studied in literature. Usually, the authors consider the graphs from some fixed class and identify within it those graphs with maximal (or minimal) index. So far maximal graphs with fixed order, or with fixed size, are identified, but not maximal connected graphs with fixed order and size. In this paper we add some new observations related to the structure of the latter graphs
On degenerate elliptic equations in Morrey spaces
Get PDFRegularity of generalized solutions to degenerate elliptic PDE’s has received a very strong impulse in the direction of finding the minimal assumptions under which regularity results hold true. Definitely, the point of view is that Lebesgue classes are not the right ones where to put lower order terms to ensure regularity
Fixed points of the Barnsley-Hutchinson operators induced by hyper-condensing maps
Get PDFThe aim of this note is to show that the Barnsley-Hutchinson operator, induced by either single h-bounded hyper-condensing map or a compact infinite family of such maps, admits a maximal fixed point and global attractor.Under suitable continuity conditions both fixed point and attractor coincide.This improves and extends several earlier results.To obtain these results some new properties of the Hausdorff measure of noncompactness on the hyperspace are established
Real curves with fixed gonality and empty real locus
Get PDFHere we give two existence theorems for smooth genus g real curves with fixed gonality and empty real locus