A classical result of J. Ph. Labrousse (Rev. Roumaine
Math. Pures Appl. 25, 1391-1394, 1980) concerning the symmetric difference
between the essential quasi-Fredholm spectrum and the Goldberg
spectrum of closed operators in Hilbert spaces is extended to the
case of B-Fredholm spectra. The obtained results are used to describe
the essential spectrum and some B-Fredholm spectra of some transport
operators.
Benharrat, Mohammed; Messirdi, Bekkai(International Journal of Analysis and Applications, 2015-08-11)
To be able to refine the completion of C (H1, H2), the of set all closed densely defined linear operators between two Hilbert spaces H1 and H2, we define in this paper some new strictly stronger metrics than the gap metric ...
Benharrat, Mohammed; Messirdi, Bekkai(Rendiconti del Circolo Matematico di Palermo, 2013-08-01)
In Kaufman (Proc Amer Math Soc 72: 531–534, 1978) proved that the function defined by maps the set $$\fancyscript{C}_{0}(H)$$ of all pure contractions one-to-one onto the set $$\fancyscript{C}(H)$$ of all closed and densely ...
Benharrat, MOHAMMED; Messirdi, BEKKAI(Univ. Oradea Fasc. Mat. XXI (1), 2014)
J. P. Labrousse [13] studied and characterized in the case of Hilbert spaces, a
relation of the essential quasi-Fredholm spectrum and the spectrum de ned by Goldberg
in [9] by ec(A) = f 2 C ; R( I A) is not closedg. ...
