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

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 $X(\mathbb{Z},w)=\{\phi :\mathbb{Z}\to \mathbb{C}:\phi w\in X(\mathbb{Z})\}$. 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 $M_{X(\mathbb{Z},w)}$.

accepted in Journal of Approximation Theory