scholarly journals Fredholm perturbations and seminorms related to upper semi-Fredholm perturbations

Filomat ◽  
2013 ◽  
Vol 27 (6) ◽  
pp. 1147-1155 ◽  
Author(s):  
Boulbeba Abdelmoumen ◽  
Hamadi Baklouti
Keyword(s):  
Fredholm Perturbations

scholarly journals Some results on Fredholm and semi-Fredholm perturbations

2014 ◽  
Vol 3 (3) ◽  
pp. 313-323 ◽  
Author(s):  
Afif Ben Amar ◽  
Aref Jeribi ◽  
Maher Mnif
Keyword(s):  
Fredholm Perturbations

Semi-Fredholm perturbations and commutators

1993 ◽  
Vol 113 (1) ◽  
pp. 173-177 ◽  
Author(s):  
Mostafa Mbekhta
Keyword(s):  
Banach Spaces ◽  
Finite Rank ◽  
Fredholm Operators ◽  
Densely Defined ◽  
Fredholm Perturbations

AbstractThe Laffey–West theorem concerning finite rank perturbations of bounded Fredholm operators is extended to closed densely defined operators on Banach Spaces.

scholarly journals Relatively compact-like perturbations, essential spectra and application

2004 ◽  
Vol 77 (1) ◽  
pp. 73-90 ◽  
Author(s):  
Khalid Latrach ◽  
J. Martin Paoli
Keyword(s):  
Banach Space ◽  
Linear Operator ◽  
Neutron Transport ◽  
Linear Operators ◽  
Essential Spectra ◽  
Graph Norm ◽  
Bounded Linear ◽  
Neutron Transport Equations ◽  
Densely Defined ◽  
Fredholm Perturbations

AbstractThe purpose of this paper is to provide a detailed treatment of the behaviour of essential spectra of closed densely defined linear operators subjected to additive perturbations not necessarily belonging to any ideal of the algebra of bounded linear operators. IfAdenotes a closed densely defined linear operator on a Banach spaceX, our approach consists principally in considering the class ofA-closable operators which, regarded as operators in ℒ(XA,X) (whereXAdenotes the domain ofAequipped with the graph norm), are contained in the set ofA-Fredholm perturbations (see Definition 1.2). Our results are used to describe the essential spectra of singular neutron transport equations in bounded geometries.

scholarly journals Remarks on embeddable semigroups in groups and a generalization of some Cuthbert's results

2003 ◽  
Vol 2003 (22) ◽  
pp. 1421-1431 ◽  
Author(s):  
Khalid Latrach ◽  
Abdelkader Dehici
Keyword(s):  
Banach Space ◽  
Fredholm Operator ◽  
Linear Operators ◽  
Sufficient Condition ◽  
Necessary And Sufficient Condition ◽  
Bounded Linear Operators ◽  
Bounded Linear ◽  
Compact Perturbations ◽  
Necessary And Sufficient ◽  
Fredholm Perturbations

Let(U(t))t≥0be aC0-semigroup of bounded linear operators on a Banach spaceX. In this paper, we establish that if, for somet0>0,U(t0)is a Fredholm (resp., semi-Fredholm) operator, then(U(t))t≥0is a Fredholm (resp., semi-Fredholm) semigroup. Moreover, we give a necessary and sufficient condition guaranteeing that(U(t))t≥0can be imbedded in aC0-group onX. Also we study semigroups which are near the identity in the sense that there existst0>0such thatU(t0)−I∈𝒥(X), where𝒥(X)is an arbitrary closed two-sided ideal contained in the set of Fredholm perturbations. We close this paper by discussing the case where𝒥(X)is replaced by some subsets of the set of polynomially compact perturbations.

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