Geometry Forum (special edition)
Tuesday, April 14, 2009, 8:30am, 227 Physics
Graham Cox (Duke University)
The Yang--Mills equations over Riemann surfaces
Abstract:
In this talk I will describe some interactions between the moduli space of stable holomorphic bundles over a Riemann surface and the space of minimal unitary Yang-Mills connections, as presented by Atiyah and Bott in their paper "The Yang-Mills Equations over Riemann Surfaces". The Yang-Mills energy will be considered as a Morse function on the space of connections, and its nullity and index computed in terms of the sheaf cohomology of certain holomorphic bundles. I will also describe how the standard holonomy correspondence can be extended to relate unitary Yang-Mills connections (not necessarily flat) to projective unitary representations of the fundamental group. Finally, a stratification of the moduli space that occurs in algebraic geometry will be presented. This is precisely the stratification one would expect from the Yang-Mills functional; however, the proof that such a Morse stratification even exists would require rather strong convergence results for the Yang-Mills gradient flow, and so this correspondence is left at a conjectural level.

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