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Some results on multi-valued weakly jungck mappings in b-metric space

Memudu Olatinwo (2008)

Open Mathematics

In this paper, the concept of multi-valued weak contraction of Berinde and Berinde [8] for the Picard iteration in a complete metric space is extended to the case of multi-valued weak contraction for the Jungck iteration in a complete b-metric space. While our main results generalize the recent results of Berinde and Berinde [8], they also extend, improve and unify several classical results pertainning to single and multi-valued contractive mappings in the fixed point theory. Our results also improve...

Some results on order weakly compact operators

Belmesnaoui Aqzzouz, Jawad Hmichane (2009)

Mathematica Bohemica

We establish some properties of the class of order weakly compact operators on Banach lattices. As consequences, we obtain some characterizations of Banach lattices with order continuous norms or whose topological duals have order continuous norms.

Some results on (strong) asymptotic Toeplitzness and Hankelness

Mehdi Nikpour (2019)

Czechoslovak Mathematical Journal

Based on the results in A. Feintuch (1989), this work sheds light upon some interesting properties of strongly asymptotically Toeplitz and Hankel operators, and relations between these two classes of operators. Indeed, among other things, two main results here are (a) vanishing Toeplitz and Hankel operators forms an ideal, and (b) finding the distance of a strongly asymptotically Toeplitz operator from the set of vanishing Toeplitz operators.

Some results on the class of σ -unbounded Dunford-Pettis operators

Noufissa Hafidi, Jawad H'michane (2021)

Commentationes Mathematicae Universitatis Carolinae

We introduce and study the class of unbounded Dunford--Pettis operators. As consequences, we give basic properties and derive interesting results about the duality, domination problem and relationship with other known classes of operators.

Some simple nonlinear PDE's without solutions

Haïm Brezis, Xavier Cabré (1998)

Bollettino dell'Unione Matematica Italiana

In questo articolo consideriamo alcune semplici equazioni a derivate parziali elittiche nonlineari, per le quali il Teorema della Funzione Inversa, se applicato in modo formale, suggerisce l'esistenza di soluzioni. Nonostante ciò, proviamo che non esistono soluzioni neppure in vari sensi deboli. Un problema modello è dato da - Δ ⁢ u = u 2 / x 2 + c in Ω , u = 0 su ∂ ⁡ Ω , dove Ω ⊂ R N , N ≥ 2 , è un dominio limitato contenente 0 . Per qualunque costante c > 0 , arbitrariamente piccola, proviamo che questo problema non ammette soluzioni distribuzionali...

Some spectral inequalities involving generalized scalar operators

B. Aupetit, D. Drissi (1994)

Studia Mathematica

In 1971, Allan Sinclair proved that for a hermitian element h of a Banach algebra and λ complex we have ∥λ + h∥ = r(λ + h), where r denotes the spectral radius. Using Levin's subordination theory for entire functions of exponential type, we extend this result locally to a much larger class of generalized spectral operators. This fundamental result improves many earlier results due to Gelfand, Hille, Colojoară-Foiaş, Vidav, Dowson, Dowson-Gillespie-Spain, Crabb-Spain, I. & V. Istrăţescu, Barnes,...

Some spectral properties of the streaming operator with general boundary conditions

Mohamed Boulanouar (2008)

Applications of Mathematics

This paper deals with the spectral study of the streaming operator with general boundary conditions defined by means of a boundary operator K . We study the positivity and the irreducibility of the generated semigroup proved in [M. Boulanouar, L’opérateur d’Advection: existence d’un C 0 -semi-groupe (I), Transp. Theory Stat. Phys. 31, 2002, 153–167], in the case ∥ K ∥ ≥ 1 . We also give some spectral properties of the streaming operator and we characterize the type of the generated semigroup in terms of the...

Some stability results in complete metric space

Memudu Olaposi Olatinwo (2009)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

In this paper, we obtain some stability results for the Picard iteration process for one and two metrics in complete metric space by using different contractive definitions which are more general than those of Berinde [Berinde, V.: On the stability of some fixed point procedures. Bul. Stiint. Univ. Baia Mare, Ser. B, Matematica–Informatica 18, 1 (2002), 7–14.], Imoru and Olatinwo [Imoru, C. O., Olatinwo, M. O.: On the stability of Picard and Mann iteration processes. Carpathian J. Math. 19, 2 (2003),...

Some stability theorems for some iteration processes

C. O. Imoru, Memudu Olaposi Olatinwo (2006)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

In this paper, we obtain some stability results for Picard and Mann iteration processes in metric space and normed linear space respectively, using two different contractive definitions which are more general than those of Harder and Hicks [4], Rhoades [10, 11], Osilike [8], Osilike and Udomene [9], Berinde [1, 2], Imoru and Olatinwo [5] and Imoru et al [6].Our results are generalizations of some results of Harder and Hicks [4], Rhoades [10, 11], Osilike [8], Osilike and Udomene [9], Berinde [1,...

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