Le Matematiche (Dipartimento di Matematica e Informatica, Università degli Studi di Catania)
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On series involving zeros of trascendental functions arising from Volterra integral equations
No full textSeries arising from Volterra integral equations of the second kind are summed. The series involve inverse powers of roots of the characteristic equation. It is shown how previous similar series obtained from differential-difference equations are particular cases of the present development. A number of novel and interesting results are obtained. The techniques are demonstrated through illustrative examples
Sulla composizione delle forme quadratiche di variabili normali in componenti sferiche
No full textSi considera il rapportotra due forme quadratiche di variabili normali indipendenti e la sua distribuzione sulla ipersfera unitaria. Viene poi ottenuta una decomposizione per forme quadratiche in termini di vettori aleatori di tipo sferico. Si ottengono infine le espressioni esatte per la densità di probabilità in alcuni casi particolari
Surfaces with defective tangential varieties
No full textSurfaces with h-defective tangential varieties are classified for any h. Smooth surfaces with this property are pointed out. It is shown that varieties of osculating (of any order) to curves are not defective
Grassman defectivity à la Terracini
No full textThis work is a modern rivisitation of a classical paper by nA. Terracini, going back to 1915, which suggests an elementary but powerful method for studying Grassmann defective varieties. In particular, the case of Veronese surfaces is completely understood, giving a positive answer to the so-called Waring problem for pairs of homogeneous polynomials in three variables
A canonical resolution of the singularities of a triple covering of algebraic surfaces
No full textWe propose a canonical resolution of singularities of a triple covering X of algebraic surfaces Y when X is normal and Y is smooth
Misurabilità, misure e integrali negli spazi di Riez Dedekind σ-completi muniti di unità debole per l\u27ordine
No full textMeasurability with respect to a δ-ring of unitary elements of a Dedekind σ-complete Riez space with a weak order unit and integrability with respect to a positive and finite measure are investigated here
On two revised nodes of S. N. Bernstein interpolating process
No full textIn this work we study the well-known problem put forward by S. N. Bernstein in 1930. We construct an operator that converges and give a bound for the best convergence order
Two properties of norms in Orlicz spaces
No full textA characterization of inclusion between L^p-spaces is well-known. Here we present an analogous characterization for Orlicz spaces. To this aim we use some definitions of Orlicz and Luxemburg norm that are a little bit general then usual. Also this allows us to extend in Orlicz spaces some properties