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Simutaneously vanishing higher derived limits without large cardinals

Published 12 Feb 2021 in math.LO and math.AT | (2102.06699v1)

Abstract: A question dating to Sibe Marde\v{s}i\'{c} and Andrei Prasolov's 1988 work Strong homology is not additive, and motivating a considerable amount of set theoretic work in the ensuing years, is that of whether it is consistent with the ZFC axioms for the higher derived limits lim<sup>n\mathrm{lim}<sup>n $(n&gt;0)$ of a certain inverse system A\mathbf{A} indexed by <sup>ωω{<sup>\omega}\omega to simultaneously vanish. An equivalent formulation of this question is that of whether it is consistent for all nn-coherent families of functions indexed by <sup>ωω{<sup>\omega}\omega to be trivial. In this paper, we prove that, in any forcing extension given by adjoining ℶω\beth_\omega-many Cohen reals, lim<sup>n</sup>A\mathrm{lim}<sup>n</sup> \mathbf{A} vanishes for all $n &gt; 0$. Our proof involves a detailed combinatorial analysis of the forcing extension and repeated applications of higher dimensional Δ\Delta-system lemmas. This work removes all large cardinal hypotheses from the main result of arXiv:1907.11744 and substantially reduces the least value of the continuum known to be compatible with the simultaneous vanishing of lim<sup>n</sup>A\mathrm{lim}<sup>n</sup> \mathbf{A} for all $n &gt; 0$.

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