Generalized vector valued almost periodic and ergodic distributions

TL;DR

This paper develops a unified framework for vector-valued almost periodic and ergodic distributions, extending classical theorems and introducing new conditions to analyze the asymptotic behavior of solutions to differential-integral equations.

Contribution

It generalizes the theory of almost periodic and ergodic distributions, introduces a new $( riangle)$-condition, and derives new Tauberian theorems for asymptotic analysis of differential-integral equations.

Findings

Characterization of almost periodic distributions in various classes.

Generalizations of Bohl-Bohr-Kadets theorem on indefinite integrals.

New Tauberian theorems for asymptotic behavior of solutions.

Abstract

For $\Cal A\subset L^1_{loc}(\Bbb J,X)$ let $\Cal M\Cal A$ consist of all $f\in L^1_{loc}$ with $ M_h f (\cdot):=\frac {1}{h}\int_{0}^{h}f(\cdot +s)\,ds \in \Cal A$ for all $h>0$. Here $X$ is a Banach space, $\Bbb J= (\alpha ,\infty), [\alpha ,\infty)$ or $\Bbb R$. Usually $\Cal A\subset\Cal M\Cal A\subset \Cal M^2\Cal A\subset ...$. The map $ \Cal A \to \Cal {D}'_{\Cal A}$ is iteration complete, that is $ \Cal {D}'_{\Cal {D}'_{\Cal A}}= \Cal {D}'_{\Cal A}$. Under suitable assumptions $\widetilde {\Cal M}^n \Cal {A}= \Cal A + \{T^{(n)} : T \in \Cal A\}$, and similarly for $\Cal {M}^n \Cal A$. Almost periodic $X$-valued distributions $\h'_{\A}$ with $\A = $ almost periodic (ap) functions are characterized in several ways. Various generalizations of the Bohl-Bohr-Kadets theorem on the almost periodicity of the indefinite integral of an ap or almost automorphic function are obtained. On $ \Cal {D}'_{\Cal E} $, $ \Cal E $ the class of ergodic functions, a mean can be constructed which gives Fourier series. Special cases of $\Cal A $ are the Bohr ap, Stepanoff ap, almost automorphic, asymptotically ap, Eberlein weakly ap, pseudo ap and (totally) ergodic functions $(\T)\E$. Then always $\Cal {M}^n \Cal A$ is strictly contained in $ \Cal {M}^{n+1} \Cal A$. The relations between $\m^n \E$, $\m^n\T\E$ and subclasses are discussed. For many of the above results a new $(\Delta)$-condition is needed, we show that it holds for most of the $\A$ needed in applications. Also, we obtain new tauberian theorems for $f\in L^1_{loc}(\Bbb J,X)$ to belong to a class $\A$ which are decisive in describing the asymptotic behavior of unbounded solutions of many abstract differential-integral equations. This generalizes various recent results