### 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

The paper's page at arxiv.org
(These are all the same modulo changes, some for the better, to conform with LMS house style.)