Results 11 to 20 of about 2,436,536 (336)
Numerical Range and Quadratic Numerical Range for Damped Systems [PDF]
, 2017 We prove new enclosures for the spectrum of non-selfadjoint operator matrices associated with second order linear differential equations $\ddot{z}(t) + D \dot{z} (t) + A_0 z(t) = 0$ in a Hilbert space.
Jacob, Birgit +3 more
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On the Numerical Range and Numerical Radius of the Volterra Operator
Известия Иркутского государственного университета: Серия "Математика", 2018 In this paper, we investigated the numerical range and the numerical radius of the classical Volterra operator on the complex space $L^2[0,1]$. In particular, we determined the numerical range, the numerical radius of real and imaginary part of the ...
L. Khadkhuu, D. Tsedenbayar
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Computing the q-Numerical Range of Differential Operators
Journal of Applied Mathematics, 2020 A linear operator on a Hilbert space may be approximated with finite matrices by choosing an orthonormal basis of thez Hilbert space. In this paper, we establish an approximation of the q-numerical range of bounded and unbounnded operator matrices by ...
Ahmed Muhammad, Faiza Abdullah Shareef
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On joint numerical ranges [PDF]
Pacific Journal of Mathematics, 1978 The joint numerical status of commuting bounded operators Ai and A2 on a Hubert space is defined as {{φiA^y φ(A2)) such that φ is a state on the C*-algebra generated by Ax and A2}. It is shown that if At and A2 are commuting normal operators then their joint numerical status equals the closure of their joint numerical range.
John J. Buoni, Bhushan L. Wadhwa
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Essential numerical range and $C$-numerical range for unbounded operators [PDF]
Studia Mathematica, 2022 Consider an unbounded operator \(T\) on a Hilbert space \(\mathcal{H}\). The authors introduce a new type of essential numerical range for \(T\), called \(W_{e5}(T)\) (essential numerical range of type 5). They show, for instance, that \(W_{e5}(T)\) is closed, convex, and contains the essential spectrum \(\sigma_e(T)\).
Hefti, Nicolas, Tretter, Christiane
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The numerical range and the essential numerical range [PDF]
Proceedings of the American Mathematical Society, 1977 A simple proof is given of Lancaster’s theorem that the convex hull of the numerical and essential numerical ranges of a Hilbert space operator is the closure of the numerical range.
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On some reciprocal matrices with elliptical components of their Kippenhahn curves
Special Matrices, 2021 By definition, reciprocal matrices are tridiagonal n-by-n matrices A with constant main diagonal and such that ai,i+1ai+1,i= 1 for i = 1, . . ., n − 1.
Jiang Muyan, Spitkovsky Ilya M.
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Joint numerical ranges: recent advances and applications minicourse by V. Müller and Yu. Tomilov
Concrete Operators, 2020 We present a survey of some recent results concerning joint numerical ranges of n-tuples of Hilbert space operators, accompanied with several new observations and remarks.
Müller V., Tomilov Yu.
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Demonstratio Mathematica, 2021 A new class of operators, larger than ∗\ast -finite operators, named generalized ∗\ast -finite operators and noted by Gℱ∗(ℋ){{\mathcal{G {\mathcal F} }}}^{\ast }\left({\mathcal{ {\mathcal H} }}) is introduced, where: Gℱ∗(ℋ)={(A,B)∈ℬ(ℋ)×ℬ(ℋ):∥TA−BT∗−λI ...
Messaoudene Hadia, Mesbah Nadia
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Investigations of the numerical range of a operator matrix
Vestnik Samarskogo Gosudarstvennogo Tehničeskogo Universiteta. Seriâ: Fiziko-Matematičeskie Nauki, 2014 We consider a $2\times2$ operator matrix $A$ (so-called generalized Friedrichs model) associated with a system of at most two quantum particles on ${\rm d}$-dimensional lattice.
Tulkin Kh Rasulov, Elyor B Dilmurodov
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