When Kalton and Peck met Fourier

Abstract

The paper studies short exact sequences of Banach modules over the convolution algebra $L_1=L_1(G)$, where $G$ is a compact abelian group. The main tool is the notion of a nonlinear $L_1$-centralizer, which in combination with the Fourier transform, is used to produce sequences of $L_1$-modules $0\to L_q\to Z\to L_p\to 0$ that are nontrivial as long as the general theory allows it, namely for $p\in (1,\infty ],q\in [1,\infty )$. Concrete examples are worked in detail for the circle group, with applications to the Hardy classes, and the Cantor group.

27 pages, 0 figures