


Paper's Title:
Hyponormal and KQuasiHyponormal Operators On SemiHilbertian Spaces
Author(s):
Ould Ahmed Mahmoud Sid Ahmed and Abdelkader Benali
Mathematics Department,
College of Science,
Aljouf University,
Aljouf 2014,
Saudi Arabia.
Email:
sididahmed@ju.edu.sa
Mathematics Department, Faculty of
Science,
Hassiba Benbouali, University of Chlef,
B.P. 151 Hay Essalem, Chlef 02000,
Algeria.
Email:
benali4848@gmail.com
Abstract:
Let H be a Hilbert space and let A be a positive bounded operator on H. The semiinner product < uv>_{A}:=<Auv>, u,v ∈ H induces a seminorm  ._{A} on H. This makes H into a semiHilbertian space. In this paper we introduce the notions of hyponormalities and kquasihyponormalities for operators on semi Hilbertian space (H,._{A}), based on the works that studied normal, isometry, unitary and partial isometries operators in these spaces. Also, we generalize some results which are already known for hyponormal and quasihyponormal operators. An operator T ∈ B_{A} (H) is said to be (A, k)quasihyponormal if
Paper's Title:
Linear System of Singularly Perturbed Initial Value Problems with Robin Initial Conditions
Author(s):
S. Dinesh, G. E. Chatzarakis, S. L. Panetsos and S. Sivamani
Department of Mathematics,
Saranathan College of Engineering,
Tiruchirappalli620012,
Tamil Nadu,
India.
Department of Electrical and Electronic
Engineering Educators,
School of Pedagogical and Technological Education,
Marousi 15122, Athens,
Greece.
Email:
geaxatz@otenet.gr,
dineshselvaraj24@gmail.com,
spanetsos@aspete.gr,
winmayi2012@gmail.com
Abstract:
On the interval (0,1], this paper considers an initial value problem for a system of n singularly perturbed differential equations with Robin initial conditions. On a piecewise uniform Shishkin mesh, a computational approach based on a classical finite difference scheme is proposed. This approach is shown to be firstorder convergent in the maximum norm uniformly in the perturbation parameters. The theory is illustrated by a numerical example.
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