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We analyze special classes of bi-orthogonal sets of vectors in Hilbert and in Krein spaces, and their relations with generalized Riesz systems. In this way, the notion of the first/second type sequences is introduced and studied. We also…

Mathematical Physics · Physics 2020-02-19 Fabio Bagarello , Sergiusz Kużel

We study orthogonally additive operators between Riesz spaces without the Dedekind completeness assumption on the range space. Our first result gives necessary and sufficient conditions on a pair of Riesz spaces $(E,F)$ for which every…

Functional Analysis · Mathematics 2022-10-19 Olena Fotiy , Vladimir Kadets , Mikhail Popov

The main result of the paper is that a system of invariant subspaces of a (completely non-unitary) Hilbert space contraction $T$ with finite defects (rank$(I-T^*T)<\infty$, rank$(I-TT^*)<\infty$) is an unconditional basis (Riesz basis) if…

Functional Analysis · Mathematics 2016-09-06 Serguei Treil

We prove that every finite union of rectangles in $R^d$ admits a Riesz basis of exponentials.

Classical Analysis and ODEs · Mathematics 2015-06-23 Gady Kozma , Shahaf Nitzan

In this paper we have some new results on sums of Hilbert space frames and Riesz bases. We also have a correction for some results in "S. Obeidat et al., Sums of Hilbert space frames, J. Math. Anal. Appl. 351 (2009) 579-585."

Functional Analysis · Mathematics 2012-07-31 A. Najati , M. R. Abdollahpour , E. Osgooei , M. M. Saem

We give necessary and sufficient conditions for a subfamily of regularly spaced translates of a function to form a frame (resp. a Riesz basis) for its span. One consequence is that ifthetranslates are taken only from a subset of the natural…

Functional Analysis · Mathematics 2007-05-23 Peter G. Casazza , Ole Christensen , Nigel J. Kalton

An orthonormal basis matrix $X$ of a subspace ${\cal X}$ is known not to be unique, unless there are some kinds of normalization requirements. One of them is to require that $X^{\rm T}D$ is positive semi-definite, where $D$ is a constant…

Numerical Analysis · Mathematics 2023-04-04 Zhongming Teng , Ren-Cang Li

Let $P_N(R)$ be the space of all real polynomials in $N$ variables with the usual inner product $<, >$ on it, given by integrating over the unit sphere. We start by deriving an explicit combinatorial formula for the bilinear form…

Number Theory · Mathematics 2009-12-14 Lenny Fukshansky

We revisit Pavlov's characterization for Riesz bases of exponentials and study the corresponding lower Riesz basis bounds. In particular, this approach allows us to improve on known estimates for the bounds in Avdonin's theorem regarding…

Classical Analysis and ODEs · Mathematics 2025-01-22 Thibaud Alemany , Shahaf Nitzan

We show that any finite union of intervals supports a Riesz basis of exponentials

Classical Analysis and ODEs · Mathematics 2014-04-16 Gady Kozma , Shahaf Nitzan

Outer product frames are important objects in Hilbert space frame theory. But very little is known about them. In this paper, we make the first detailed study of the family of outer product frames induced directly by vector sequences. We…

Functional Analysis · Mathematics 2014-10-31 Peter G. Casazza , Eric Pinkham , Brian Tuomanen

It is known that if $\Omega \subset \mathbb{R}^{d}$ belongs to a class of multi-tiling domains when translated by a lattice $\Lambda$, there exists a Riesz basis of exponentials for $L^{2}(\Omega)$ constructed using $k$ translates of the…

Classical Analysis and ODEs · Mathematics 2020-07-28 Christina Frederick , Kasso Okoudjou

In~\cite{holub1994bases} Holub introduced the concept of near-Riesz bases, as frames that can be considered Riesz bases for computational purposes or that exhibit certain desirable properties of Riesz bases. In this paper, we introduce a…

Functional Analysis · Mathematics 2025-10-23 Deborpita Biswas , Mishko Mitkovski

In this paper, we present the concept of continuous biframes in a Hilbert space. We examine the essential properties of biframes with an emphasis on the biframe operator. Moreover, we introduce a new type of Riesz bases, referred to as…

Functional Analysis · Mathematics 2023-12-13 Hafida Massit , Roumaissae Eljazzar , Mohamed Rossafi

We give a simple and short proof of the classical Lebesgue decomposition theorem of measures via the Riesz orthogonal decomposition theorem of Hilbert spaces. The tools we employ are elementary Hilbert space techniques.

Functional Analysis · Mathematics 2014-03-24 Zsigmond Tarcsay

We give a comprehensive introduction to a general modular frame construction in Hilbert C*-modules and to related modular operators on them. The Hilbert space situation appears as a special case. The reported investigations rely on the idea…

Operator Algebras · Mathematics 2025-05-08 Michael Frank , David R. Larson

We discuss existence and stability of Riesz bases of exponential type of L^2(T) for special domains T called trapezoids. We construct exponential bases on L^2(T) when T is a finite union of rectangles with the same height. We also…

Functional Analysis · Mathematics 2013-06-20 Laura De Carli , Anudeep Kumar

Given a positive weight function and an isometry map on a Hilbert spaces $\mathcal{H}$, we study a class of linear maps which is a $g$-frame, $g$-Riesz basis and a $g$-orthonormal basis for $\mathcal{H}$ with respect to $\mathbb{C}$ in…

Functional Analysis · Mathematics 2020-04-09 Anirudha Poria

We study the basis property of systems of exponentials with frequencies belonging to 'simple quasicrystals'. We show that a diophantine condition is necessary and sufficient for such a system to be a Riesz basis in L^2 on a finite union of…

Classical Analysis and ODEs · Mathematics 2011-03-15 Gady Kozma , Nir Lev

Weaving frames have potential applications in wireless sensor networks that require distributed processing of signal under different frames. In this paper, we study some new properties of weaving generalized frames (or $g$-frames) and…

Functional Analysis · Mathematics 2021-02-22 Deepshikha , Aniruddha Samanta
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