Zobrazeno 1 - 10
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pro vyhledávání: '"Yakubovich, Dmitry"'
We provide a complete characterization of those non-elliptic semigroups of holomorphic self-maps of the unit disc for which the linear span of eigenvectors of the generator of the corresponding semigroup of composition operators is weak-star dense in
Externí odkaz:
http://arxiv.org/abs/2311.17470
We prove that in a large class of Banach spaces of analytic functions in the unit disc $\mathbb{D}$ an (unbounded) operator $Af=G\cdot f'+g\cdot f$ with $G,\, g$ analytic in $\mathbb{D}$ generates a $C_0$-semigroup of weighted composition operators i
Externí odkaz:
http://arxiv.org/abs/2110.05247
Autor:
Bello, Glenier, Yakubovich, Dmitry
For an invertible linear operator $T$ on a Hilbert space $H$, put \[ \alpha(T^*,T) := -T^{*2}T^2 + (1+r^2) T^* T - r^2 I, \] where $I$ stands for the identity operator on $H$ and $r\in (0,1)$; this expression comes from applying Agler's hereditary fu
Externí odkaz:
http://arxiv.org/abs/2106.08757
We study the generalization of $m$-isometries and $m$-contractions (for positive integers $m$) to what we call $a$-isometries and $a$-contractions for positive real numbers $a$. We show that any Hilbert space operator, satisfying an inequality of cer
Externí odkaz:
http://arxiv.org/abs/2005.00075
We discuss when an operator, subject to a rather general inequality in hereditary form, admits a unitarily equivalent functional model of Agler type in the reproducing kernel Hilbert space associated to the inequality. To the contrary to the previous
Externí odkaz:
http://arxiv.org/abs/1908.05032
Autor:
Putinar, Mihai, Yakubovich, Dmitry
Finite rank perturbations $T=N+K$ of a bounded normal operator $N$ on a separable Hilbert space are studied thanks to a natural functional model of $T$; in its turn the functional model solely relies on a perturbation matrix/ characteristic function
Externí odkaz:
http://arxiv.org/abs/1907.13587
Publikováno v:
Complex Analysis and Operator Theory (2019) 13:1325-1360
Let $T$ be a bounded linear operator on a Hilbert space $H$ such that \[ \alpha[T^*,T]:=\sum_{n=0}^\infty \alpha_n T^{*n}T^n\ge 0. \] where $\alpha(t)=\sum_{n=0}^\infty \alpha_n t^n$ is a suitable analytic function in the unit disc $\mathbb{D}$ with
Externí odkaz:
http://arxiv.org/abs/1711.05110
Publikováno v:
Israel J. Math. 229 (2019), no. 1, 487-500
Avicou, Chalendar and Partington proved that an (unbounded) operator $(Af)=G\cdot f'$ on the classical Hardy space generates a $C_0$ semigroup of composition operators if and only if it generates a quasicontractive semigroup. Here we prove that if su
Externí odkaz:
http://arxiv.org/abs/1708.02259
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
Autor:
Pal, Avijit, Yakubovich, Dmitry V.
Given a Hilbert space operator $T$, the level sets of function $\Psi_T(z)=\|(T-z)^{-1}\|^{-1}$ determine the so-called pseudospectra of $T$. We set $\Psi_T$ to be zero on the spectrum of $T$. After giving some elementary properties of $\Psi_T$ (which
Externí odkaz:
http://arxiv.org/abs/1609.08325