Keiho Matsumoto

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20222026

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3 papers · 2 filters

math.AG2026

Voevodsky motives and motives with modulus with finite coefficients in characteristic zero

Keiho Matsumoto

Let $k$ be a field of characteristic zero and let $n \geq 2$ be an integer. We prove that, with $Z / n Z$ -coefficients, the category of effective motives with modulus is equivalent t…

math.AG2026

Degeneration Theorems of Connes and Feigin--Tsygan Type in Mixed Characteristic, with q-Analogues

Keiho Matsumoto

We prove mixed-characteristic analogues of the Connes and Feigin--Tsygan degeneration theorem. Let $W = W (k)$ be the Witt vectors of a perfect field of characteristic $p > 0$ . For a sm…

math.AG2026

A Criterion for Phantomness of dg-categories

Keiho Matsumoto

We study the question of whether the vanishing of additive invariants characterizes phantomness for smooth proper dg categories admitting geometric realizations. More precisely, le…