On multiplier analogues of the algebra $C+H^\infty$ on weighted rearrangement-invariant sequence spaces

TL;DR

This paper investigates the structure of multiplier algebras related to weighted rearrangement-invariant sequence spaces, establishing their Banach algebra properties and the closedness of certain subalgebras generated by trigonometric polynomials and Hardy-type functions.

Contribution

It introduces and analyzes multiplier algebras on weighted rearrangement-invariant sequence spaces, proving they form Banach algebras and identifying closed subalgebras related to trigonometric polynomials and Hardy spaces.

Findings

$M_{X(bZ,w)}$ is a Banach algebra.

The closures of trigonometric polynomials form closed subalgebras.

Subalgebras $C_{X(bZ,w)}$ and $H_{X(bZ,w)}^{ty, pm}$ are closed in $M_{X(bZ,w)}$.

Abstract

Let $X(\mathbb{Z})$ be a reflexive rearrangement-invariant Banach sequence space with nontrivial Boyd indices $\alpha_X,\beta_X$ and let $w$ be a symmetric weight in the intersection of the Muckenhoupt classes $A_{1/\alpha_X}(\mathbb{Z})$ and $A_{1/\beta_X}(\mathbb{Z})$. Let $M_{X(\mathbb{Z},w)}$ denote the collection of all periodic distributions $a$ generating bounded Laurent operators $L(a)$ on the space $X(\mathbb{Z},w)=\{\varphi:\mathbb{Z}\to\mathbb{C}:\varphi w\in X(\mathbb{Z})\}$. We show that $M_{X(\mathbb{Z},w)}$ is a Banach algebra. Further, we consider the closure of trigonometric polynomials in $M_{X(\mathbb{Z},w)}$ denoted by $C_{X(\mathbb{Z},w)}$ and $H_{X(\mathbb{Z},w)}^{\infty,\pm}= \{a\in M_{X(\mathbb{Z},w)}:\widehat{a}(\pm n)=0 \mbox{ for }n<0\}$. We prove that $C_{X(\mathbb{Z},w)}+H_{X(\mathbb{Z},w)}^{\infty,\pm}$ are closed subalgebras of $M_{X(\mathbb{Z},w)}$.