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pro vyhledávání: '"Dritschel, Michael A."'
Autor:
Contino, Maximiliano, Dritschel, Michael A., Maestripieri, Alejandra, Marcantognini, Stefania
On finite dimensional spaces, it is apparent that an operator is the product of two positive operators if and only if it is similar to a positive operator. Here, the class ${\mathcal L}^{+2}$ of bounded operators on separable infinite dimensional Hil
Externí odkaz:
http://arxiv.org/abs/2007.00680
Akademický článek
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Autor:
Dritschel, Michael A.
It is shown using Schur complement techniques that on finite dimensional Hilbert spaces, a non-negative operator valued trigonometric polynomial in two variables with degree $(d_1,d_2)$ can be written as a finite sum of hermitian squares of at most $
Externí odkaz:
http://arxiv.org/abs/1811.06005
It is shown that rational dilation fails on broad collection of distinguished varieties associated to constrained subalgebras of the disk algebra of the form C + B A(D), where B is a finite Blaschke product with two or more zeros. This is accomplishe
Externí odkaz:
http://arxiv.org/abs/1711.11090
Publikováno v:
J. Math. Anal. Appl. 463 (2018), no. 1, 345-364
We give some new criteria for a Hilbert space operator with spectrum on a smooth curve to be similar to a normal operator, in terms of pointwise and integral estimates of the resolvent. These results generalize criteria of Stampfli, Van Casteren and
Externí odkaz:
http://arxiv.org/abs/1704.08135
Let $\Phi$ be a family of functions analytic in some neighborhood of a complex domain $\Omega$, and let $T$ be a Hilbert space operator whose spectrum is contained in $\overline\Omega$. Our typical result shows that under some extra conditions, if th
Externí odkaz:
http://arxiv.org/abs/1510.08350
Given a complex domain $\Omega$ and analytic functions $\varphi_1,\ldots,\varphi_n : \Omega \to \mathbb{D}$, we give geometric conditions for $H^\infty(\Omega)$ to be generated by functions of the form $g \circ \varphi_k$, $g \in H^\infty(\mathbb{D})
Externí odkaz:
http://arxiv.org/abs/1505.01838
Autor:
Dritschel, Michael A.
We extend Agler's notion of a function algebra defined in terms of test functions to include products, in analogy with the practice in real algebraic geometry, and hence the term preordering in the title. This is done over abstract sets and no additi
Externí odkaz:
http://arxiv.org/abs/1503.01319
It is well known that unital contractive representations of the disk algebra are completely contractive. Let A denote the subalgebra of the disk algebra consisting of those functions f whose first derivative vanishes at 0. We prove that there are uni
Externí odkaz:
http://arxiv.org/abs/1305.4272
We introduce completely bounded kernels taking values in L(A,B) where A and B are C*-algebras. We show that if B is injective such kernels have a Kolmogorov decomposition precisely when they can be scaled to be completely contractive, and that this i
Externí odkaz:
http://arxiv.org/abs/1001.3590