XXV Workshop on Geometric Methods in Physics 2-8.07.2006

Kirill Mackenzie


For any Poisson structure on a smooth manifold M the bracket of functions induces a bracket of 1--forms which makes the cotangent bundle T^*M a Lie algebroid. On the other hand, for any Lie group G there is a Lie groupoid structure on T^*G with base manifold the dual of the Lie algebra. It is a basic fact that a Poisson structure on a Lie group G makes G a Poisson Lie group if and only if the two structures on T^*G commute in the categorical sense, that is, if and only if T^*G is a Lie groupoid object in the category of Lie algebroids.

This observation shows that the Drinfel'd double of the Lie bialgebra is a double in the categorical sense, as well as in the sense of Drinfel'd. We will describe this and further applications of the method to Poisson actions.