Galois theory and integral models of Lambda-rings

J. Borger, B. de Smit, Galois theory and integral models of Lambda-rings, Bulletin of the London Mathematical Society 2008; doi: 10.1112/blms/bdn024

Abstract: We show that any Λ-ring, in the sense of Riemann--Roch theory, which is finite étale over the rational numbers and has an integral model as a Λ-ring is contained in a product of cyclotomic fields. In fact, we show that the category of such Λ-rings is described in a Galois-theoretic way in terms of the monoid of pro-finite integers under multiplication and the cyclotomic character. We also study the maximality of these integral models and give a more precise, integral version of the result above. These results reveal an interesting relation between Λ-rings and class field theory.

Published LMS version: here
The pre-LMS pdf: here

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