Ehsan Rashidi | Searcharxiv

arXiv2019

Dynamical sampling: mixed frame operators, representations and perturbations

Motivated by recent progress in operator representation of frames, we investigate the frames of the form $ \{T^n φ\}_{n\in I}$ for $ I=\mathbb{N}, \mathbb{Z} $, and answer questions about representations, perturbations and frames induced by the action of powers of bounded linear operators. As a particular case, we discuss problems concerning representation of frames in terms of iterations of the mixed frame operators. As our another contribution, we consider frames of the form $ \{a_n T^n φ\}_{n=0}^{\infty} $ for some non-zero scalars $ \{a_n\}_{n=0}^{\infty} $, and we obtain some new results in dynamical sampling. Finally, we will present some auxiliary results related to the perturbation of sequences of the form $ \{T^n φ\}_{n=0}^{\infty}$.

math.FA↗

arXiv2018

Dynamical sampling and frame representations with bounded operators

The purpose of this paper is to study frames for a Hilbert space ${\cal H},$ having the form $\{T^n φ\}_{n=0}^\infty$ for some $φ\in {\cal H}$ and an operator $T: {\cal H} \to {\cal H}.$ We characterize the frames that have such a representation for a bounded operator $T,$ and discuss the properties of this operator. In particular, we prove that the image chain of $T$ has finite length $N$ in the overcomplete case; furthermore $\{T^n φ\}_{n=0}^\infty$ has the very particular property that $\{T^n φ\}_{n=0}^{N-1} \cup \{T^n φ\}_{n=N+\ell}^\infty$ is a frame for ${\cal H} $ for all $\ell\in {\mathbf N}_0$. We also prove that frames of the form $\{T^n φ\}_{n=0}^\infty$ are sensitive to the ordering of the elements and to norm-perturbations of the generator $φ$ and the operator $T.$ On the other hand positive stability results are obtained by considering perturbations of the generator $φ$ belonging to an invariant subspace on which $T$ is a contraction.

math.FA↗