Le Matematiche (Dipartimento di Matematica e Informatica, Università degli Studi di Catania)
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On higher secant varieties of rational normal scrolls
Get PDFIn this paper we study the higher secant varieties of rational normal scrolls, in particular we give them as determinantal varieties. From this we can obtain, in some cases, the sequence of secant defects, generalizing to a class of varieties and to every characteristic the counterexample given by Ådlandsvik to Zak\u27s theorem of superadditivity
Ordinary differential equations in affine geometry
Get PDFThe method of qualitative analysis is used, as applied to a class of fourth order, nonlinear ordinary differential equations, in order to classify, both locally and globally, two classes of hypersurfaces of decomposable type in affine geometry: those with constant unimodular affine mean curvature L , and those with constant Riemannian scalar curvature R. This allows to provide a large number of new examples of hypersurfaces in affine geometry
Decomposizione ed s-m rappresentazione di gruppi finiti
No full textThis paper is a survey of a few previous works of the authors with other new results. We introduce a special decomposition of a finite group [semigroup] and determine its main properties. From such a decomposition one can construct, for a special class of finite groups, a set-matrix representation. The group D_4 has such a representation. Several theorems were already obtained on groups with s-m representation
On the existence of cycles of every even length on generalized Fibonacci cubes
No full textA new topology for the interconnection of computing nodes in multiprocessors systems is the generalized Fibonacci cube.It can be embedded as a subgraph in the Boolean cube and it is also a supergraph of other structures. We prove that every edge of such a graph, but few initial cases, belongs to cycles of every even length
Elliptic equations with discontinuous coefficients in unbounded domains of R^2
Get PDFIn this paper we are concerned with second order elliptic equations in unbounded domains Ω of R^2 . We establish existence and uniqueness theorems under the assumptions that the leading coefficients are bounded and measurable in Ω and satisfy a suitable condition at infinity
On equational properties of subgroup lattices of metabelian groups
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Space-time finite elements numerical solutions of Burgers Problems
Get PDFA finite-element numerical method to solve a weak formulation of quasi-linear parabolic problems on space-time domain governed by Burgers equation is given. Stability and errors estimates theorems for the numerical solution are proved for smooth initial conditions and numerical examples are presented
Ample vector bundles with sections vanishing on surfaces of Kodaira dimension zero
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