Le Matematiche (Dipartimento di Matematica e Informatica, Università degli Studi di Catania)
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Vector Bundles of Low rank on a Multiprojective Space
Get PDFIn this paper we construct vector bundles over a multiprojective space and study their properties. We first set out to establish the existence of monads on a multiprojective space X. Then, we study the vector bundles associated to these monads
Periodic solutions for a second order nonlinear neutral functional differential equation with variable delay
Get PDFIn this paper we study the existence of periodic solutions of the second order nonlinear neutral differential equation with functional delay. We invert the given equation to obtain an integral, but equivalent, equation from which we define a fixed point mapping written as a sum of a large contraction and a compact map. We show that, under suitable conditions, such maps fit very nicely into the framework of Krasnoselskii-Burton\u27s fixed point theorem so that the existence of periodic solutions is concluded
Thermo-elastic plane deformations in doubly-connected domains with temperature and pressure which depend of the thermal conductivity
Get PDFWe propose a new weak formulation for the plane problem of thermoelastic theory in multiply-connected domains. This permits to avoid the difficulties connected with the Cesaro-Volterra boundary conditions in the related elliptic boundary-value problem. In the second part we consider a nonlinear version of the problem assuming that the thermal conductivity depends not only on the temperature but also on the pressure. Recent studies reveals that this situation can occur in practice. A theorem of existence and uniqueness is proved for this problem
Classes of spirallike functions defined by the Dziok-Srivastava operator
Get PDFMaking use of the Dziok-Srivastava operator, we introduce two classes of analytic functions and investigate convolution properties, the necessary and sufficient condition, coefficient estimates and inclusion properties for these classes
Minimax solutions for a problem with sign changing nonlinearity and lack of strict convexity
Get PDFA result of existence of a nonnegative and a nontrivial solution is proved via critical point theorems for non smooth functionals. The equation considered presents a convex part and a nonlinearity which changes sign
Rational cuspidal curves with four cusps on Hirzebruch surfaces
Get PDFThe purpose of this article is to shed light on the question of how many and what kind of cusps a rational cuspidal curve on a Hirzebruch surface can have. Our main result is a list of rational cuspidal curves with four cusps, their type, cuspidal congurations and the surfaces they lie on. We use birational transformations to construct these curves. Moreover, we find a general expression for and compute the Euler characteristic of the logarithmic tangent sheaf in these cases. Additionally, we show that there exists a real rational cuspidal curve with four real cusps. Last, we show that for rational cuspidal curves with two or more cusps on a Hirzebruch surface, there is a lower bound on one of the multiplicities
Equivalence of the convergences of T-Picard, T-Mann and T-Ishikawa iterations for the class of T-Zamfirescu operators
Get PDFIn this paper, we prove the equivalence between the convergences of T-Picard iteration, T-Mann iteration and T-Ishikawa iteration for the class ofT-Zamfirescu operators in normed linear spaces. Our results extend and improvethe results of Solutz and Zhiqun
A generalized variational principle in b-metric spaces
Get PDFIn this paper we establish and prove a generalized variational principle for b-metric spaces. As a consequence, we obtain a weak Zhong-type variational principle in b-metric spaces. We show the applicability of the mentioned generalized variational principle by presenting a Caristi-type fixed point theorem and an extension of the main result for bifunctions - both of them stated in b-metric spaces
Mapping properties a general integral operator defined by the Hadamard product
Get PDFIn the present paper, we introduce a general integral operator defined by Hadamard product and study mapping properties on some subclasses of analytic univalent functions. Relevant connections of the results presented here with various known results are briefly indicated
New fractional inequalities of Ostrowski-Grüss type
Get PDFIn this paper, we improve and further generalize some Ostrowski-Grüss type inequalities for the fractional integrals by using new Montogomery identities