Abstract
We give a new construction, based on categorical logic, of Nori’s \(\mathbb Q\)-linear abelian category of mixed motives associated to a cohomology or homology functor with values in finite-dimensional vector spaces over \(\mathbb Q\). This new construction makes sense for infinite-dimensional vector spaces as well, so that it associates a \(\mathbb Q\)-linear abelian category of mixed motives to any (co)homology functor, not only Betti homology (as Nori had done) but also, for instance, \(\ell \)-adic, p-adic or motivic cohomology. We prove that the \(\mathbb Q\)-linear abelian categories of mixed motives associated to different (co)homology functors are equivalent if and only a family (of logical nature) of explicit properties is shared by these different functors. The problem of the existence of a universal cohomology theory and of the equivalence of the information encoded by the different classical cohomology functors thus reduces to that of checking these explicit conditions.
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Barbieri-Viale, L., Caramello, O. & Lafforgue, L. Syntactic categories for Nori motives. Sel. Math. New Ser. 24, 3619–3648 (2018). https://doi.org/10.1007/s00029-018-0425-z
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DOI: https://doi.org/10.1007/s00029-018-0425-z