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2009
If B(H) is the algebra of bounded linear operators on a Hilbert space (H) and K is the ideal of compact operators on (H), one forms the Calkin algebra B(H)/K and the natural map π: B(H) → B(H)/K. Recall that A∈B(H) is Fredholm if π(A) is invertible in B(H)/K. A well-known theorem [19, p.
Alexandru Aleman +2 more
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If B(H) is the algebra of bounded linear operators on a Hilbert space (H) and K is the ideal of compact operators on (H), one forms the Calkin algebra B(H)/K and the natural map π: B(H) → B(H)/K. Recall that A∈B(H) is Fredholm if π(A) is invertible in B(H)/K. A well-known theorem [19, p.
Alexandru Aleman +2 more
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The Clinical Spectrum of Essential Hypertension
Archives of Internal Medicine, 1974The majority of hypertensive patients fall into the borderline and mild groups. A smaller percentage of the hypertensive population falls into the groups with persistent elevations in diastolic blood pressure of 105 mm Hg or higher. However, they are a most important group because treatment has been effective in reducing their high risk of developing ...
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On the Essential Spectrum of Quantum Graphs
Integral Equations and Operator Theory, 2017This paper studies the spectral theory of Schrödinger operators which are defined on a metric graph, embedded in \(\mathbb{R}^n\), which has a periodic structure in the sense that it is invariant under translations defined by of a subgroup of \(\mathbb{R}^n\) isomorphic to \(\mathbb{Z}^m\) (i.e. a lattice).
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Spectrum of a Model Operator in the Perturbation Theory of the Essential Spectrum
Theoretical and Mathematical Physics, 2005zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Yodgorov, G. R., Muminov, M. E.
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On the Linear Essential Spectrum Operator
2018This paper presents: Let A be a unital \(C^{*}\)-algebra of real rank zero and B be a unital semisimple complex Banach algebra. We characterize linear maps from A onto B that compress different essential spectral sets such as the (left, right) essential spectrum, the semi-Fredholm spectrum, and the Weyl spectrum.
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On the Essential Spectrum of a Differentially Rotating Star
ZAMM, 1999The authors study the essential spectrum of a family \(L_{k,0}\) (\(k\in {\mathbb Z}\)) of mixed order partial differential operators which arise after separation of variables in the linearised Euler equation. Such an equation could be a model for natural oscillation of a differentially rotating stars.
Faierman, M. +3 more
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The Essential Spectrum of Some Matrix Operators
Mathematische Nachrichten, 1994From authors' introduction: We consider operators \(L_0\) defined by a \(2\times 2\) block operator matrix \[ L_0= \left(\begin{matrix} A & B\\ C & D\end{matrix}\right),\tag{\(*\)} \] where the entries are in general unbounded operators, \(A\) acting in a Banach space \(X_1\), \(D\) acting in a Banach space \(X_2\), and \(B\), \(C\) acting between ...
Atkinson, F. V. +3 more
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On the Unboundedness of the Essential Spectrum
American Journal of Mathematics, 1952openaire +2 more sources
Essential spectrum of upper triangular operator matrices
Annals of Functional Analysis, 2020Junjie Huang, Xiufeng Wu
exaly