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September 2005 Covariant Honda theory
Oleg Demchenko
Tohoku Math. J. (2) 57(3): 303-319 (September 2005). DOI: 10.2748/tmj/1128702999


Honda's theory gives an explicit description up to strict isomorphism of formal groups over perfect fields of characteristic $p\neq 0$ and over their rings of Witt vectors by means of attaching a certain matrix, which is called its type, to every formal group. A dual notion of right type connected with the reduction of the formal group is introduced while Honda's original type becomes a left type. An analogue of the Dieudonné module is constructed and an equivalence between the categories of formal groups and right modules satisfying certain conditions, similar to the classical anti-equivalence between the categories of formal groups, and left modules satisfying certain conditions is established. As an application, the $\star$-isomorphism classes of the deformations of a formal group over and the action of its automorphism group on these classes are studied.


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Oleg Demchenko. "Covariant Honda theory." Tohoku Math. J. (2) 57 (3) 303 - 319, September 2005.


Published: September 2005
First available in Project Euclid: 7 October 2005

zbMATH: 1127.14041
MathSciNet: MR2154095
Digital Object Identifier: 10.2748/tmj/1128702999

Primary: 11S31
Secondary: 14L05

Rights: Copyright © 2005 Tohoku University


Vol.57 • No. 3 • September 2005
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