Derived $q$-Hodge complexes and refined $\operatorname{TC}^-$ (2410.23115v3)

Abstract: As a consequence of Efimov's proof of rigidity of the $\infty$-category of localising motives, Scholze and Efimov have constructed refinements of localising invariants such as $\operatorname{TC}^-$. In this article we compute the homotopy groups of the refined invariants $\operatorname{TC}^{-,\mathrm{ref}}(\mathrm{ku}\otimes\mathbb Q/\mathrm{ku})$ and $\operatorname{TC}^{-,\mathrm{ref}}(\mathrm{KU}\otimes\mathbb Q/\mathrm{KU})$. The computation involves a surprising connection to $q$-de Rham cohomology. In particular, it suggests a construction of a $q$-Hodge filtration on $q$-de Rham complexes in certain situations, which can be used to construct a functorial derived $q$-Hodge complex for many rings. This is in contrast to a no-go result by the second author, who showed that such a $q$-Hodge complex (and thus also a $q$-Hodge filtration) cannot exist in full generality.