Le Matematiche  

Fausto De Mari, Francesco De Giovanni

It is proved that a group G has ?nitely many normalizers of non-subnormal subgroups if and only if each subgroup of G either is subnormal or has ?nitely many conjugates; groups with this latter property have been completely described in [8]. Moreover, gro... see more

M. M. El-Borai, M. A. Abdou, M. Basseem

In this article, a numerical method is used to solve the two dimensionalFredholm integral equation of the second kind with weak singular kernel using the Toeplitz matrix and product Nystrom method. The numerical results given in this paper are computed us... see more

Ali Mahmud Ateiwi

We study problems related to the existence of a nondegenerate substitution(of the Lyapunov type) that reduces a system of linear difference equationsto a system with constant coefficients.

A. M. Hassanein

In this paper we study the transfer of some algebraic properties from the ring R to the ring of skew Hurwitz series T = (H R, s ) where s  is an automorphism of R and vice versa. We show that T = (H R, s ) is a clean (strongly clean) ring if and only... see more

Meri Lisi

In this paper, some results and generalizations about the Cantor pairingfunction are given. In particular, it is investigated a very compact expressionfor the n-degree generalized Cantor pairing function (g.C.p.f., for short), thatpermits to obtain n-tupl... see more

Caterina La Russa

In this paper we study suitable notions of porosity and directional porosity in Fréchet spaces. Moreover we give a decomposition theorem for s-P-directionally porous sets.

Jorge Caravantes

The aim of this paper is to extend a theorem of Griffiths, Harris and Hulek [4], [6] on the extendability of divisors of a smooth complete intersection surface in P^n to the case when the ambient space is a product of projective spaces or a Grassmannian. ... see more

Paola Bonacini, Alessio Del Padrone, Michele Nesci

In 1980, Faltings proved, by deep local algebra methods, a local resultregarding formal functions which has the following global geometric factas a consequence. Theorem. - Let k be an algebraically closed field (ofany characteristic). Let Y be a closed su... see more

Naim L. Braha

Corrigendum of Lemma 3 (Le Matematiche vol. 60 Fasc. 1, 2005, pp. 121-128)

Maria Artale

The Durfee square of a partition ?, D(?), is defined as the largest square contained in the shape of ?.It was proved in [2] (cf. also [3]) that the size of D(?), d(?), was related to the perfection of a certain module M_? , an algebro-geometric object (cf... see more

Edoardo Ballico, Francesco Malaspina

Let X be a smooth Fano manifold equipped with a “ nice ” n-blocks collection in the sense of [3] and F a coherent sheaf on X . Assume that X is Fano and that all blocks are coherent sheaves. Here we prove that F has regularity -8 in the sense of [3] if Su... see more

Giuseppe Rao, Francesco Tulone

An analogue of classical Dini-Riemann theorem related to non-absolutelyconvergent series of real number is proved for the Lebesgue improper integral.

Roberta Volpicelli, Bruno Volzone

We consider the solution u of the Cauchy-Dirichlet problem for a class of linear parabolic equations in which the coefficient of the zero order term could have a singularity at the origin of the type 1/|x|^2 . We prove that u can be compared “in the sense... see more