Results 11 to 20 of about 694 (64)
Spectrum perturbations of compact operators in a Banach space
Open Mathematics, 2019 For an integer p ≥ 1, let Γp be an approximative quasi-normed ideal of compact operators in a Banach space with a quasi-norm NΓp(.) and the ...
Gil’ Michael
doaj +1 more source
On a problem in eigenvalue perturbation theory [PDF]
, 2015 We consider additive perturbations of the type $K_t=K_0+tW$, $t\in [0,1]$, where $K_0$ and $W$ are self-adjoint operators in a separable Hilbert space $\mathcal{H}$ and $W$ is bounded.
Gesztesy, Fritz +2 more
core +1 more source
On the spectra of non‐selfadjoint differential operators and their adjoints in direct sum spaces
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 9, Page 557-574, 2003., 2003 The general ordinary quasidifferential expression Mp of nth order, with complex coefficients and its formal adjoint Mp+ on any finite number of intervals Ip = (ap, bp), p = 1, …, N, are considered in the setting of the direct sums of Lwp2(ap,bp)‐spaces of functions defined on each of the separate intervals.
Sobhy El-Sayed Ibrahim
wiley +1 more source
On the domain of selfadjoint extension of the product of Sturm‐Liouville differential operators
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 11, Page 695-709, 2003., 2003 The second‐order symmetric Sturm‐Liouville differential expressions τ1, τ2, …, τn with real coefficients are considered on the interval I = (a, b), −∞ ≤ a < b ≤ ∞. It is shown that the characterization of singular selfadjoint boundary conditions involves the sesquilinear form associated with the product of Sturm‐Liouville differential expressions and ...
Sobhy El-Sayed Ibrahim
wiley +1 more source
Finite rank perturbations and solutions to the operator Riccati equation [PDF]
, 2015 We consider an off-diagonal self-adjoint finite rank perturbation of a self-adjoint operator in a complex separable Hilbert space $\mathfrak{H}_0 \oplus \mathfrak{H}_1$, where $\mathfrak{H}_1$ is finite dimensional.
Großmann, Julian P.
core +1 more source
USING PERTURBATION METHODS AND LAPLACE-PAD´ E APPROXIMATION TO SOLVE NONLINEAR PROBLEMS
, 2013 In this paper, the perturbation method and Padtransformation are used to provide an approximate solution of elliptic integrals of the second kind and of complete integrals of the first kind.
U. Filobello-Nino +7 more
semanticscholar +1 more source
A spectral mapping theorem for semigroups solving PDEs with nonautonomous past
Abstract and Applied Analysis, Volume 2003, Issue 16, Page 933-951, 2003., 2003 We prove a spectral mapping theorem for semigroups solving partial differential equations with nonautonomous past. This theorem is then used to give spectral conditions for the stability of the solutions of the equations.
Genni Fragnelli
wiley +1 more source
Weyl's theorem and its perturbations for the functions of operators
, 2018 In this paper, we study the stability of Weyl’s theorem under compact perturbations, and characterize those operators satisfying that the stability of Weyl’s theorem does not hold for any integer powers of the operator. Mathematics subject classification
X. Cao, Jiong Dong, Jun Liu
semanticscholar +1 more source
A Note on Property $(gb)$ and Perturbations [PDF]
, 2012 An operator T ∈ B(X) defined on a Banach space X satisfies property (gb) if the complement in the approximate point spectruma(T) of the upper semi-B-Weyl spectrumSBF + (T) coincides with the set (T) of all poles of the resolvent of T.
Qingping Zeng, H. Zhong
semanticscholar +1 more source
Kreĭn′s trace formula and the spectral shift function
International Journal of Mathematics and Mathematical Sciences, Volume 25, Issue 4, Page 239-252, 2001., 2001 Let A, B be two selfadjoint operators whose difference B − A is trace class. Kreĭn proved the existence of a certain function ξ ∈ L1(ℝ) such that tr[f(B) − f(A)] = ∫ℝf′(x)ξ(x)dx for a large set of functions f. We give here a new proof of this result and discuss the class of admissible functions.
Khristo N. Boyadzhiev
wiley +1 more source