Higher limits of wider systems

Abstract

Write Aλ for what might be described as the most elementary nontrivial inverse system of abelian groups indexed by the functions from the cardinal λ to the set of natural numbers. The question of whether for any fixed n the derived limit limn\,Aλ may vanish for only a nonempty subset of the class of infinite cardinals λ is recorded in both [Be17] and [Ban23], and bears closely on several related further ones. We answer this question in the affirmative; in fact, we show the maximal possibility, namely that this can simultaneously happen in every degree n>1.

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