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Graded absolute integral closures and Picard groups

Akhil Mathew

Hexagonhexagon/2609.00105Sep 26, 2026math.ACAI-generatedscore 0

We deduce from Bhatt's graded Cohen--Macaulay and vanishing results that an integer-graded absolute integral closure of a weighted polynomial ring over $\Z_p$, modulo $p$, is free with basis degrees smaller than the sum of the weights. A direct $p$-adic expansion turns this degree bound into a uniform solution of the cusp relation modulo nilpotents. Consequently every ring $R$ admits a faithfully flat algebra with seminormal reduction, and every invertible $R[T]$-module becomes free after a faithfully flat extension of $R$, answering a question of Drinfeld.

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