In this paper‎, ‎we show the stability of Gustafson‎, ‎Weidmann‎, ‎Kato‎, ‎Wolf‎, ‎Schechter and Browder essential spectrum of bounded linear operators on Banach spaces which remain invariant under additive perturbations‎ ‎belonging to a broad classes of operators $U$ such $gamma(U^m)

in this paper‎, ‎we show the stability of gustafson‎, ‎weidmann‎, ‎kato‎, ‎wolf‎, ‎schechter and browder essential spectrum of bounded linear operators on banach spaces which remain invariant under additive perturbations‎ ‎belonging to a broad classes of operators $u$ such $gamma(u^m)

We study spectral properties of unbounded Jacobi matrices with periodically modulated or blended entries. Our approach is based on uniform asymptotic analysis generalized eigenvectors. determine when the studied operators are self-adjoint. identify regions where point spectrum has no accumulation points. This allows us to completely describe essential these operators.

A continuation approach to the computation of essential and absolute spectra of reaction-diffusion operators on the real line is presented. The advantage of this approach compared with direct eigenvalue computations for the discretized operator are the efficient and accurate computation of selected parts of the spectrum (typically those near the imaginary axis) and the option to compute nonline...

Let A be a closed, densely defined operator in a Banach space X. There are several definitions of the "essential" spectrum of A (cf. [ l ] , [2]). According to Wolf [3], [4] it is the complement in the complex plane of the $-set of A. The $-set $A of A is the set of points X for which (a) a(A — X), the dimension of the null space of A — X, is finite (b) R(A —X), the range of A —X, is closed (c)...

If T and S are quasisimilar bounded operators on Banach spaces, we prove that each closed-and-open subset of the lower semiBrowder essential spectrum of T intersects one special part of the upper semi-Browder essential spectra of T and S. AMS Mathematics Subject Classification (1991): 47A53, 47A10

The B̃-X̃ laser-induced-fluorescence spectrum of jet-cooled isopropoxy radical (i-C3H7O[middle dot]) has been recorded. Using an isolated state model the observed rotational and fine structure of the origin band has been well simulated to determine rotational constants for both the X̃ and B̃ states and the electron spin-rotation constants of the X̃ state. The line intensities are well simulated with...