Results 31 to 40 of about 8,384 (123)

Riesz bases of exponentials on multiband spectra [PDF]

, 2011
Let $S$ be the union of finitely many disjoint intervals on the real line. Suppose that there are two real numbers $\alpha, \beta$ such that the length of each interval belongs to $Z \alpha + Z \beta$.
Lev, Nir
core   +1 more source

Inverse Problem for a Fourth-Order Hyperbolic Equation with a Complex-Valued Coefficient

Mathematics, 2023
This paper studies the existence and uniqueness of the classical solution of inverse problems for a fourth-order hyperbolic equation with a complex-valued coefficient with Dirichlet and Neumann boundary conditions.
Asselkhan Imanbetova, Abdissalam Sarsenbi, Bolat Seilbekov   +2 more
doaj   +1 more source

New Characterizations of Riesz Bases

Applied and Computational Harmonic Analysis, 1997
Using the projection method for frames [\textit{O. Christensen}, Appl. Comput. Harmon. Anal. 1, No. 1, 50-53 (1993; Zbl 0849.42025)] this paper gives two equivalent conditions for a frame to be a Riesz basis in a separable Hilbert space. These conditions emerge from taking the limit in a sequence of nested finite dimensional subspaces.
Kim, Hong Oh, Lim, Jae Kun
openaire   +2 more sources

Riesz bases and positive operators on Hilbert space

International Journal of Mathematics and Mathematical Sciences, 2003
It is shown that a normalized Riesz basis for a Hilbert space H (i.e., the isomorphic image of an orthonormal basis in H) induces in a natural way a new, but equivalent, inner product on H in which it is an orthonormal basis, thereby extending the sense ...
James R. Holub
doaj   +1 more source

Approximate Duals of $g$-frames and Fusion Frames in Hilbert $C^ast-$modules [PDF]

Sahand Communications in Mathematical Analysis, 2019
In this paper, we study approximate duals of $g$-frames and fusion frames in Hilbert $C^ast-$modules. We get some relations between approximate duals of $g$-frames and biorthogonal Bessel sequences, and using these relations, some results for approximate
Morteza Mirzaee Azandaryani
doaj   +1 more source

A note on exponential Riesz bases

Sampling Theory, Signal Processing, and Data Analysis, 2022
AbstractWe prove that if$$I_\ell = [a_\ell ,b_\ell )$$Iℓ=[aℓ,bℓ),$$\ell =1,\ldots ,L$$ℓ=1,…,L, are disjoint intervals in [0, 1) with the property that the numbers$$1, a_1, \ldots , a_L, b_1, \ldots , b_L$$1,a1,…,aL,b1,…,bLare linearly independent over$${\mathbb {Q}}$$Q, then there exist pairwise disjoint sets$$\Lambda _\ell \subset {\mathbb {Z}}$$Λℓ⊂Z,$
Andrei Caragea, Dae Gwan Lee
openaire   +3 more sources

Weaving Riesz Bases

Journal of Fourier Analysis and Applications
This paper explores woven frames in separable Hilbert spaces with an initial focus on the finite-dimensional case. We begin by simplifying the problem to bases, for which we obtain a unique characterization. We establish a condition that is both necessary and sufficient for vector reconstruction, which applies to Fourier matrices.
C. Cabrelli, U. Molter, F. Negreira
openaire   +3 more sources

Characterizing the R-duality of g-frames

Journal of Inequalities and Applications, 2019
In this paper, we define the g-Riesz-dual of a given special operator-valued sequence with respect to g-orthonormal bases for a separable Hilbert space.
Liang Li, Pengtong Li
doaj   +1 more source

Fractal Frames of Functions on the Rectangle

Fractal and Fractional, 2021
In this paper, we define fractal bases and fractal frames of L2(I×J), where I and J are real compact intervals, in order to approximate two-dimensional square-integrable maps whose domain is a rectangle, using the identification of L2(I×J) with the ...
María A. Navascués, Ram Mohapatra, Md. Nasim Akhtar   +2 more
doaj   +1 more source

p-Riesz bases in quasi shift invariant spaces

, 2017
Let $ 1\leq p< \infty$ and let $\psi\in L^{p}(\R^d)$. We study $p-$Riesz bases of quasi shift invariant spaces $V^p(\psi;Y)$
De Carli, Laura, Vellucci, Pierluigi
core   +1 more source