Herbert Kurke

Commuting differential operators and higher-dimensional algebraic varieties

Several algebro-geometric properties of commutative rings of partial differential operators (PDOs) as well as several geometric constructions are investigated. In particular, we show how to associate a geometric data by a commutative ring of PDOs, and we investigate the properties of these geometric data. This construction is in some sense similar to the construction of a formal module of Baker–Akhieser functions. On the other hand, there is a recent generalization of Sato’s theory, which belongs to the third author of this paper. We compare both approaches to the commutative rings of PDOs in two variables. As a by-product, we get several necessary conditions on geometric data describing commutative rings of PDOs.

Formal punctured ribbons and two-dimensional local fields

Abstract We investigate formal ribbons on curves. Roughly speaking, formal ribbon is a family of locally linearly compact vector spaces on a curve. We establish a one-to-one correspondence between formal ribbons on curves plus some geometric data and some subspaces of two-dimensional local fields.

Formal Groups Arising from Formal Punctured Ribbons

We investigate the Picard functor of a formal punctured ribbon. We prove that under some conditions this functor is representable by a formal group scheme.