Monodromy group for a strongly semistable principal bundle over a curve. II

Biswas, Indranil ; Parameswaran, A. J. (2008) Monodromy group for a strongly semistable principal bundle over a curve. II Journal of K-Theory, 1 (3). pp. 583-607. ISSN 1865-2433

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Official URL: http://journals.cambridge.org/action/displayAbstra...

Related URL: http://dx.doi.org/10.1017/is007011017jkt015

Abstract

Let X be a geometrically irreducible smooth projective curve defined over a field k. Assume that X has a k-rational point; fix a k-rational point x ε X. From these data we construct an affine group scheme X defined over the field k as well as a principal X-bundle S1755069607000151inline1 over the curve X. The group scheme X is given by a xs0211A-graded neutral Tannakian category built out of all strongly semistable vector bundles over X. The principal bundle S1755069607000151inline1 is tautological. Let G be a linear algebraic group, defined over k, that does not admit any nontrivial character which is trivial on the connected component, containing the identity element, of the reduced center of G. Let EG be a strongly semistable principal G-bundle over X. We associate to EG a group scheme M defined over k, which we call the monodromy group scheme of EG, and a principal M-bundle EM over X, which we call the monodromy bundle of EG. The group scheme M is canonically a quotient of X, and EM is the extension of structure group of S1755069607000151inline1. The group scheme M is also canonically embedded in the fiber Ad(EG)x over x of the adjoint bundle.

Item Type:Article
Source:Copyright of this article belongs to Cambridge University Press.
Keywords:Neutral Tannakian Category; Principal Bundle; Semistability
ID Code:35418
Deposited On:04 Jul 2012 13:30
Last Modified:04 Jul 2012 13:30

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