Displaying similar documents to “The algebraic fundamental group of a reductive group scheme over an arbitrary base scheme”

Flasque resolutions of reductive group schemes

Cristian González-Avilés (2013)

Open Mathematics

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We generalize Colliot-Thélène’s construction of flasque resolutions of reductive group schemes over a field to a broad class of base schemes.

Higher order invariants in the case of compact quotients

Anton Deitmar (2011)

Open Mathematics

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We present the theory of higher order invariants and higher order automorphic forms in the simplest case, that of a compact quotient. In this case, many things simplify and we are thus able to prove a more precise structure theorem than in the general case.

Fragmented deformations of primitive multiple curves

Jean-Marc Drézet (2013)

Open Mathematics

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A primitive multiple curve is a Cohen-Macaulay irreducible projective curve Y that can be locally embedded in a smooth surface, and such that Y red is smooth. We study the deformations of Y to curves with smooth irreducible components, when the number of components is maximal (it is then the multiplicity n of Y). We are particularly interested in deformations to n disjoint smooth irreducible components, which are called fragmented deformations. We describe them completely. We give also...

Tame stacks in positive characteristic

Dan Abramovich, Martin Olsson, Angelo Vistoli (2008)

Annales de l’institut Fourier

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We introduce and study a class of algebraic stacks with finite inertia in positive and mixed characteristic, which we call tame algebraic stacks. They include tame Deligne-Mumford stacks, and are arguably better behaved than general Deligne-Mumford stacks. We also give a complete characterization of finite flat linearly reductive schemes over an arbitrary base. Our main result is that tame algebraic stacks are étale locally quotient by actions of linearly reductive finite group schemes. ...

Forcing in the alternative set theory. II

Jiří Sgall, Antonín Sochor (1991)

Commentationes Mathematicae Universitatis Carolinae

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By the technique of forcing, some new independence results are proved for the alternative set theory (AST) and similar weak theories: The scheme of choice is independent both of AST and of second order arithmetic, axiom of constructibility is independent of AST plus schemes of choice.