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In this paper, structural properties of lower semi-frames in separable Hilbert spaces are explored with a focus on transformations under linear operators (may be unbounded). Also, the direct sum of lower semi-frames, providing necessary and…

Functional Analysis · Mathematics 2025-04-18 Hemalatha M , P. Sam Johnson , Harikrishnan P. K

In this work, we stress the existence of isomorphisms which map complex contours from the upper half to contours in the lower half of the complex plane. The metric operator is found to depend on the chosen contour but the maps connecting…

Mathematical Physics · Physics 2014-10-23 Abouzeid Shalaby

We find sharp bounds for the norm inequality on a Pseudo-hermitian manifold, where the L^2 norm of all second derivatives of the function involving horizontal derivatives is controlled by the L^2 norm of the sub-Laplacian. Perturbation…

Analysis of PDEs · Mathematics 2007-05-23 Sagun Chanillo , Juan J. Manfredi

We consider perturbed nonlinear ill-posed equations in Hilbert spaces, with operators that are monotone on a given closed convex subset. A simple stable approach is Lavrentiev regularization, but existence of solutions of the regularized…

Numerical Analysis · Mathematics 2018-06-05 Robert Plato , Bernd Hofmann

We introduce the so called convex body valued sparse operators, which generalize the notion of sparse operators to the case of spaces of vector valued functions. We prove that Calder\'on--Zygmund operators as well as Haar shifts and…

Classical Analysis and ODEs · Mathematics 2017-05-22 Fedor Nazarov , Stefanie Petermichl , Sergei Treil , Alexander Volberg

The description of all correct restrictions of the maximal operator are considered in a Hilbert space. A class of correct restrictions are obtained for which a similar transformation has the domain of the fixed correct restriction. The…

Spectral Theory · Mathematics 2021-03-11 B. N. Biyarov

Quantum splines are curves in a Hilbert space or, equivalently, in the corresponding Hilbert projective space, which generalize the notion of Riemannian cubic splines to the quantum domain. In this paper, we present a generalization of this…

Mathematical Physics · Physics 2018-11-21 L. Abrunheiro , M. Camarinha , J. Clemente-Gallardo , J. C. Cuchí , P. Santos

This paper refines the main results from our previous study on sparse bounds of generalized commutators of multilinear fractional singular integral operators in \cite{CenSong2412}. The key improvements are: 1. We replace pointwise…

Classical Analysis and ODEs · Mathematics 2025-05-27 Xi Cen

We prove that scalar-valued sparse domination of a multilinear operator implies vector-valued sparse domination for tuples of quasi-Banach function spaces, for which we introduce a multilinear analogue of the UMD condition. This condition…

Classical Analysis and ODEs · Mathematics 2024-05-31 Emiel Lorist , Zoe Nieraeth

We compute the $\delta$-invariant of a curve singularity parameterized by generic sparse polynomials. We apply this to describe topological types of generic singularities of sparse resultants and ``algebraic knot diagrams'' (i.e. generic…

Algebraic Geometry · Mathematics 2023-01-31 Alexander Esterov , Evgeny Statnik , Arina Voorhaar

We prove the equivariant holomorphic Morse inequalities for a holomorphic torus action on a holomorphic vector bundle over a compact Kahler manifold when the fixed-point set is not necessarily discrete. Such inequalities bound the twisted…

dg-ga · Mathematics 2016-08-31 Siye Wu , Weiping Zhang

This paper presents a solution to a problem from superanalysis about the existence of Hilbert-Banach superalgebras. Two main results are derived: 1) There exist Hilbert norms on some graded algebras (infinite-dimensional superalgebras…

funct-an · Mathematics 2007-05-23 Joachim Kupsch , Oleg G. Smolyanov

Beltran \& Cladek~\cite{BC} use $L^r$ to $L^s$ bounds to prove sparse form bounds for pseudodifferential operators with H\"ormander symbols in $S^m_{\rho,\delta}$ up to, but not including, the sharp end-point in decay $m$. We further…

Classical Analysis and ODEs · Mathematics 2026-04-22 Solange Mukeshimana , David Rule

We prove the boundedness of the maximal operator and Hilbert transform along certain variable parabolas in $L^p$ for $p>p_0$ with some $p_0\in (1, 2)$. Connections with the Hilbert transform along vector fields and the polynomial Carleson's…

Classical Analysis and ODEs · Mathematics 2015-05-04 Shaoming Guo

As a corollary to our main theorem we give a new proof of the result that the norm of the Hilbert transform on L^2(w) has norm bounded by a the A_2 characteristic of a weight to the first power, a theorem of one of us. This new proof begins…

Classical Analysis and ODEs · Mathematics 2012-05-04 Michael T. Lacey , Stefanie Petermichl , Maria Carmen Reguera

In this paper we characterize the surjective linear variation norm isometries on JB-algebras. Variation norm isometries are precisely the maps that preserve the maximal deviation, the quantum analogue of the standard deviation, which plays…

Operator Algebras · Mathematics 2019-06-21 Mark Roelands , Marten Wortel

A sequence of operators $T_n$ from a Hilbert space ${\mathfrak H}$ to Hilbert spaces ${\mathfrak K}_n$ which is nondecreasing in the sense of contractive domination is shown to have a limit which is still a linear operator $T$ from…

Functional Analysis · Mathematics 2024-01-02 Seppo Hassi , Henk de Snoo

Let $M$ be a von Neumann algebra with a faithful normal finite trace $t$, and $H^\infty$ be a finite, maximal, subdiagonal of $M$. Fundamental theorems on conjugate functions for weak* Dirichlet algebras are shown to be a bounded linear map…

Functional Analysis · Mathematics 2016-09-07 Narcisse Randrianantoanina

The Hilbert scheme of n points in the projective plane parameterizes degree n zero-dimensional subschemes of the projective plane. We examine the dual cones of effective divisors and moving curves on the Hilbert scheme. By studying…

Algebraic Geometry · Mathematics 2012-03-05 Jack Huizenga

We study the typical behavior of bounded linear operators on infinite dimensional complex separable Hilbert spaces in the norm, strong-star, strong, weak polynomial and weak topologies. In particular, we investigate typical spectral…

Functional Analysis · Mathematics 2014-05-01 Tanja Eisner , Tamas Matrai