Characterization of decay rates for discrete operator semigroups

Fuente: arXiv
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Main Author: Wakaiki, Masashi
Format: Preprint
Published: 2024
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author Wakaiki, Masashi
author_facet Wakaiki, Masashi
contents Let $T$ be a power-bounded linear operator on a Hilbert space $X$, and let $S$ be a bounded linear operator from another Hilbert space $Y$ to $X$. We investigate the non-exponential rate of decay of $\|T^nS\|$ as $n \to \infty$. First, when $X = Y$ and $S$ commutes with $T$, we characterize the decay rate of $\|T^nS\|$ in terms of the growth rate of $\|(λI - T)^{-k}S\|$ as $|λ| \downarrow 1$ for some $k \in \mathbb{N}$. Next, we provide another characterization by means of an integral estimate of $\|(λI - T)^{-k}S\|$. The second characterization is then applied to asymptotic estimates for perturbed discrete operator semigroups. Finally, we present some results on the relation between the decay rate of $\|T^nS\|$ and the boundedness of the sum $\sum_{n=1}^{\infty} f(n)\|T^nSy\|^p$ for all $y \in Y$ in the Banach space setting, where $f \colon \mathbb{N} \to(0,\infty)$ and $p \geq 1$.
format Preprint
id arxiv_https___arxiv_org_abs_2412_19534
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Characterization of decay rates for discrete operator semigroups
Wakaiki, Masashi
Functional Analysis
Optimization and Control
Let $T$ be a power-bounded linear operator on a Hilbert space $X$, and let $S$ be a bounded linear operator from another Hilbert space $Y$ to $X$. We investigate the non-exponential rate of decay of $\|T^nS\|$ as $n \to \infty$. First, when $X = Y$ and $S$ commutes with $T$, we characterize the decay rate of $\|T^nS\|$ in terms of the growth rate of $\|(λI - T)^{-k}S\|$ as $|λ| \downarrow 1$ for some $k \in \mathbb{N}$. Next, we provide another characterization by means of an integral estimate of $\|(λI - T)^{-k}S\|$. The second characterization is then applied to asymptotic estimates for perturbed discrete operator semigroups. Finally, we present some results on the relation between the decay rate of $\|T^nS\|$ and the boundedness of the sum $\sum_{n=1}^{\infty} f(n)\|T^nSy\|^p$ for all $y \in Y$ in the Banach space setting, where $f \colon \mathbb{N} \to(0,\infty)$ and $p \geq 1$.
title Characterization of decay rates for discrete operator semigroups
topic Functional Analysis
Optimization and Control
url https://arxiv.org/abs/2412.19534