Additive Mappings Preserving Fredholm Operators with Fixed Nullity or Defect

2021 ◽  
Vol 41 (5) ◽  
pp. 1670-1678
Author(s):  
Ruihan Zhang ◽  
Weijuan Shi ◽  
Guoxing Ji
Author(s):  
Najat Muthana ◽  
◽  
Asma Ali ◽  
Kapil Kumar

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Julián López-Gómez ◽  
Juan Carlos Sampedro

Abstract This paper generalizes the classical theory of perturbation of eigenvalues up to cover the most general setting where the operator surface 𝔏 : [ a , b ] × [ c , d ] → Φ 0 ⁢ ( U , V ) {\mathfrak{L}:[a,b]\times[c,d]\to\Phi_{0}(U,V)} , ( λ , μ ) ↦ 𝔏 ⁢ ( λ , μ ) {(\lambda,\mu)\mapsto\mathfrak{L}(\lambda,\mu)} , depends continuously on the perturbation parameter, μ, and holomorphically, as well as nonlinearly, on the spectral parameter, λ, where Φ 0 ⁢ ( U , V ) {\Phi_{0}(U,V)} stands for the set of Fredholm operators of index zero between U and V. The main result is a substantial extension of a classical finite-dimensional theorem of T. Kato (see [T. Kato, Perturbation Theory for Linear Operators, 2nd ed., Class. Math., Springer, Berlin, 1995, Chapter 2, Section 5]).


1988 ◽  
Vol 198 (3) ◽  
pp. 431-434 ◽  
Author(s):  
M�che�l � Searc�id

2003 ◽  
Vol 367 ◽  
pp. 213-224 ◽  
Author(s):  
Wu Jing ◽  
Pengtong Li ◽  
Shijie Lu

Author(s):  
Zbigniew Gajda
Keyword(s):  

In this paper we answer a question of Th. M. Rassias concerning an extension of validity of his result proved in [3].


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