Le Matematiche (Dipartimento di Matematica e Informatica, Università degli Studi di Catania)
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Ossevazioni sulla dualità per operatori Booleani
No full textWe extend the duality theory enstablished by Jònsson-Tarski-Halmos for Boolean hemimorphisms to a wider theory and we give some preliminary results
Simple wave solutions for a radiation dominated magnetofluid
No full textSimple waves are studied for a radiating magnetofluid in special relativity. For some of the Riemann invariants explicit expressions are given. The behaviour of these solutions is also studied numerically
The nonlinear continuum traffic equilibrium problem and a related Dirichlet problem for quasilinear elliptic equations
No full textIn the framework of continuum models, a system-optimization problem for transportation networks is studied in nonlinear case. Some results of convex analysis are used to prove the existence theorems and to derive variational inequalities for optimal flow. A nonhomogeneous Dirichlet problem is proved to solve the minimization problem, provided that some non standard conditions on first derivatives of the solutions are fulfilled
Symmetrization in a Neumann problem
No full textLet w be a weak solution of the Neumann problem for a second order elliptic equation in divergence form, in abounded open subset G of Rn . In the case that the right hand side of the equation is a continuous linear functional on H1(G) , we give some symmetrization results and an estimate of the norm of w
Un 3-disegno associato ad una n-fibrazione di PG(2n+1,q)
No full textIn this paper we prove that a total n-spread of PG(2n+1,q) gives us a new 3-design. Moreover, in the case n=1 we construct some new 2-design using spreads
Further properties of the zeros of Bessel functions
No full textNew monotonicity and convexity properties for the zeros cνk (k=1,2,...) of the Bessel functions are proved. New inequalities for cνk are also given. These inequalities are useful for small values of ν
Completeness and decidability of the deducibility problem for some class of formulas of set theory
No full textAn extension of results on the decidability of classes of formulas in set theory is proved. In particular a class of restricted quantified formulas is proved to be decidable also in the case in which the underlying axiomatic set theory does not contain the axiom of foundation. For all the classes considered is also studied whether or not they result to be not only decidable, but also complete and a simple decidable but not complete class of formulas is presented
3-varietà di Fano in G(1,4)
No full textLet V be a Fano threefold of genus one (i.e. with Pic(V)≃Z). Let G be the Grassmannian of the lines of ℙ4 . We study when it is possible to embed V in G , in such cases we determine the cohomology class of V in H*(G)
Existence theorems for completely non convex problems
No full textIn this note we give some existence theorems for integral functionals with non convex integrand. We consider first the simpler case in which minimization is taken on decomposable spaces and successively we prove an existence theorem also for the minimum of an integral functional on non-decomposable space