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Integrable Systems Associated to a Hopf Surface

Published online by Cambridge University Press:  20 November 2018

Ruxandra Moraru*
Affiliation:
Department of Mathematics and Statistics, McGill University, 805 Sherbrooke Street West, Montreal, Quebec H3A 2K6 e-mail: moraru@math.mcgill.ca
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Abstract

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A Hopf surface is the quotient of the complex surface ${{\mathbb{C}}^{2}}\,\backslash \,\left\{ 0 \right\}$ by an infinite cyclic group of dilations of ${{\mathbb{C}}^{2}}$. In this paper, we study the moduli spaces ${{\mathcal{M}}^{n}}$ of stable $\text{SL}\left( 2,\,\mathbb{C} \right)$-bundles on a Hopf surface $\mathcal{H}$, from the point of view of symplectic geometry. An important point is that the surface $\mathcal{H}$ is an elliptic fibration, which implies that a vector bundle on $\mathcal{H}$ can be considered as a family of vector bundles over an elliptic curve. We define a map $G:\,{{\mathcal{M}}^{n}}\,\to \,{{\mathbb{P}}^{2n+1}}$ that associates to every bundle on $\mathcal{H}$ a divisor, called the graph of the bundle, which encodes the isomorphism class of the bundle over each elliptic curve. We then prove that the map $G$ is an algebraically completely integrable Hamiltonian system, with respect to a given Poisson structure on ${{\mathcal{M}}^{n}}$. We also give an explicit description of the fibres of the integrable system. This example is interesting for several reasons; in particular, since the Hopf surface is not Kähler, it is an elliptic fibration that does not admit a section.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2003

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