Duality for double iterated outer $L^p$ spaces

TL;DR

This paper investigates the structure of double iterated outer L^p spaces, establishing conditions for their isomorphism to Banach spaces and duality properties, with results extending from finite sets to infinite settings.

Contribution

It proves the isomorphism and duality of double iterated outer L^p spaces under certain conditions, extending known results to infinite settings beyond finite sets.

Findings

Double iterated outer L^p spaces are isomorphic to Banach spaces under certain conditions.

Duality properties hold for these spaces, confirming their Banach space structure.

Counterexamples show uniformity does not hold in all finite set scenarios.

Abstract

We study the double iterated outer $L^p$ spaces, namely the outer $L^p$ spaces associated with three exponents and defined on sets endowed with a measure and two outer measures. We prove that in the case of finite sets, under certain conditions between the outer measures, the double iterated outer $L^p$ spaces are isomorphic to Banach spaces uniformly in the cardinality of the set. We achieve this by showing the expected duality properties between them. We also provide counterexamples demonstrating that the uniformity does not hold in any arbitrary setting on finite sets, at least in a certain range of exponents. We prove the isomorphism to Banach spaces and the duality properties between the double iterated outer $L^p$ spaces also in the upper half $3$-space infinite setting described by Uraltsev, going beyond the case of finite sets.