نتایج جستجو برای: positive operator matrices
تعداد نتایج: 813167 فیلتر نتایج به سال:
Classes of non-Hermitian operators that have only real eigenvalues are presented. Such operators appear in quantum mechanics and are expressed in terms of the generators of the Weyl-Heisenberg algebra. For each non-Hermitian operator A, a Hermitian involutive operator Ĵ such that A is Ĵ-Hermitian, that is, ĴA = AĴ , is found. Moreover, we construct a positive definite Hermitian Q such that A is...
We consider discretizations of the hyper-singular integral operator on closed surfaces and show that the inverses of the corresponding system matrices can be approximated by blockwise low-rank matrices at an exponential rate in the block rank. We cover in particular the data-space format of H-matrices. We show the approximability result for two types of discretizations. The first one is a saddl...
Let $A$ be a positive (semidefinite) operator on complex Hilbert space $\mathcal{H}$ and let $\mathbb{A}=\left(\begin{array}{cc} A & O O A \end{array}\right).$ We obtain upper lower bounds for the $A$-Davis-Wielandt radius of semi-Hilbertian operators, which generalize improve existing ones. also $\mathbb{A}$-Davis-Wielandt $2 \times 2$ matrices. Finally, we determine exact value two matr...
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