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In this work, we prove that linear bounded operators $T$ on a Banach space $X$ allowing spectral cuts along rectifiable Jordan curves meeting their spectrum are related to classes of operators admitting an unconventional functional…

Functional Analysis · Mathematics 2026-03-24 Eva A. Gallardo-Gutiérrez , F. Javier González-Doña

Using the notion of $S_\xi$-strictly singular operator introduced by Androulakis, Dodos, Sirotkin and Troitsky, we define an ordinal index on the subspace of strictly singular operators between two separable Banach spaces. In our main…

Functional Analysis · Mathematics 2009-08-11 Kevin Beanland

Sz.-Nagy's famous theorem states that a bounded operator $T$ which acts on a complex Hilbert space $\mathcal{H}$ is similar to a unitary operator if and only if $T$ is invertible and both $T$ and $T^{-1}$ are power bounded. There is an…

Functional Analysis · Mathematics 2016-04-05 György Pál Gehér

In this paper, we consider the trace theorem for modulation spaces, alpha modulation spaces and Besov spaces. For the modulation space, we obtain the sharp results.

Functional Analysis · Mathematics 2008-12-02 Hans Feichtinger , Chunyan Huang , Baoxiang Wang

Consider a Lipschitz domain $\Omega$ and a measurable function $\mu$ supported in $\overline\Omega$ with $\left\|{\mu}\right\|_{L^\infty}<1$. Then the derivatives of a quasiconformal solution of the Beltrami equation $\overline{\partial} f…

Classical Analysis and ODEs · Mathematics 2016-12-19 Martí Prats

For a domain $\Omega$ in a geodesically convex surface, we introduce a scattering energy $\mathcal{E}(\Omega)$, which measures the asymmetry of $\Omega$ by quantifying its incompatibility with an isometric circle action. We prove several…

Differential Geometry · Mathematics 2021-10-15 Joseph Ansel Hoisington , Peter McGrath

Starting from a thorough analysis of the conjugate $\overline{H}$ of a complex Hilbert space $H$, including its significant importance regarding a representation of the tensor product of two complex Hilbert spaces and its impact to the…

Quantum Physics · Physics 2026-05-18 Frank Oertel

We introduce a new approach to traces on the principal ideal $\mathcal L_{1,\infty}$ generated by any positive compact operator whose singular value sequence is the harmonic sequence. Distinct from the well-known construction of J.~Dixmier,…

Operator Algebras · Mathematics 2016-12-15 Evgenii Semenov , Fedor Sukochev , Aleksandr Usachev , Dmitriy Zanin

Let $V\subset \mathbb{C}\mathbb{P}^n$ be an irreducible complex projective variety of complex dimension $v$ and let $g$ be the K\"ahler metric on $\reg(V)$, the regular part of $V$, induced by the Fubini Study metric of…

Differential Geometry · Mathematics 2016-03-14 Francesco Bei

We refine the well-known Blanco-Koldobsky-Turn\v{s}ek Theorem which states that a norm one linear operator defined on a Banach space is an isometry if and only if it preserves orthogonality at every element of the space. We improve the…

Functional Analysis · Mathematics 2026-02-10 Jayanta Manna , Kalidas Mandal , Kallol Paul , Debmalya Sain

We consider the question of whether a domain with uniformly thick boundary at all locations and at all scales has a large portion of its boundary visible from the interior; here, "visibility" indicates the existence of John curves…

Metric Geometry · Mathematics 2026-03-09 Sylvester Eriksson-Bique , Ryan Gibara , Riikka Korte , Nageswari Shanmugalingam

Similar to the theory of finite Markov chains it is shown that in a Banach space $X$ ordered by a closed cone $K$ with nonempty interior int($K$) a power bounded positive operator $A$ with compact power such that its trajectories for…

Functional Analysis · Mathematics 2019-01-15 Boris M. Makarow , Martin R. Weber

We show that if a rearrangement invariant Banach function space $E$ on the positive semi-axis satisfies a non-trivial lower $q-$ estimate with constant $1$ then the corresponding space $E(\nm)$ of $\tau-$measurable operators, affiliated…

Functional Analysis · Mathematics 2016-09-06 Peter G. Dodds , T. K. Dodds , Paddy N. Dowling , Christopher J. Lennard , Fyodor A. Sukochev

We prove trace theorems for weighted mixed norm Sobolev spaces in the upper-half space where the weight is a power function of the vertical variable. The results show the differentiability order of the trace functions depends only on the…

Analysis of PDEs · Mathematics 2022-05-11 Tuoc Phan

In a bounded domain $G$ with smooth border studied boundary value and spectral problems for operators of the rotor (vortex) and the gradient of the divergence $+\lambda\,I$ in the Sobolev spaces. For $\lambda\neq 0$ these operators are…

Analysis of PDEs · Mathematics 2019-12-02 Romen S. Saks

In this paper we relate the generator property of an operator $A$ with (abstract) generalized Wentzell boundary conditions on a Banach space $X$ and its associated (abstract) Dirichlet-to-Neumann operator $N$ acting on a "boundary" space…

Functional Analysis · Mathematics 2018-11-28 Tim Binz , Klaus-Jochen Engel

The existence of right inverses of the divergence as an operator form $H^1_0(\Omega)^n$ to $L_0^2(\Omega)$ is a problem that has been widely studied because of its importance in the analysis of the classic equations of fluid dynamics. When…

Analysis of PDEs · Mathematics 2011-03-22 Ricardo G. Duran

We consider the operator algebra $\mathscr A$ on $\mathscr S(\mathbb R^n)$ generated by the Shubin type pseudodifferential operators, the Heisenberg-Weyl operators and the lifts of the unitary operators on $\mathbb C^n$ to metaplectic…

Functional Analysis · Mathematics 2022-04-13 Anton Savin , Elmar Schrohe

Let $K$ be an absolutely convex infinite-dimensional compact in a Banach space $\mathcal{X}$. The set of all bounded linear operators $T$ on $\mathcal{X}$ satisfying $TK\supset K$ is denoted by $G(K)$. Our starting point is the study of the…

Functional Analysis · Mathematics 2009-12-15 M. I. Ostrovskii , V. S. Shulman

Quantization of the Teichm\"uller space of a punctured Riemann surface $S$ is an approach to $3$-dimensional quantum gravity, and is a prototypical example of quantization of cluster varieties. Any simple loop $\gamma$ in $S$ gives rise to…

Geometric Topology · Mathematics 2023-04-05 Hyun Kyu Kim , Thang T. Q. Lê , Miri Son