Atomic representations in function spaces and applications to pointwise multipliers and diffeomorphisms, a new approach

TL;DR

This paper extends atomic decompositions in function spaces to provide a simpler proof for theorems on pointwise multipliers and diffeomorphisms, achieving more general results than previous approaches.

Contribution

It generalizes atomic decompositions for Besov and Triebel-Lizorkin spaces, enabling a concise proof of key theorems with broader applicability.

Findings

Atomic decompositions are extended for broader classes of function spaces.

A shorter, more general proof of theorems on pointwise multipliers and diffeomorphisms is provided.

The approach simplifies previous complex proofs using local means.

Abstract

In Chapter 4 of [25] Triebel proved two theorems concerning pointwise multipliers and diffeomorphisms in function spaces of Besov and Triebel-Lizorkin type. In each case he presented two approaches, one via atoms and one via local means. While the approach via atoms was very satisfactory concerning the length and simplicity, only the rather technical approach via local means proved the theorems in full generality. In this paper we generalize two extensions of these atomic decompositions, one by Skrzypczak (see [22]) and one by Triebel and Winkelvoss (see [30]) so that we are able to give a short proof using atomic representations getting an even more general result than in the two theorems in [25]. References: [22] L. Skrzypczak. Atomic decompositions on manifolds with bounded geometry. Forum Math., 10(1):19-38, 1998. [25] H. Triebel. Theory of Function Spaces II. Birkh\"auser, Basel, 1992. [30] H. Triebel and H. Winkelvo{\ss}. Intrinsic atomic characterizations of function spaces on domains. Math. Z., 221(1):647-673, 1996.