In this paper, we describe an example of a hyperkaehler quotient of a Banach manifold by a Banach Lie group. Although the initial manifold is not diffeomorphic to a Hilbert manifold (not even to a manifold modelled on a reflexive Banach space), the quotient space obtained is a Hilbert manifold, which can furthermore be identified either with the cotangent space of a connected component of the restricted grassmannian or with a natural complexification of this connected component, thus proving that these two manifolds are isomorphic hyperkaehler manifolds. In addition, Kaehler potentials are computed using Kostant-Souriau's theory of prequantization.
@article{hal-00022117,
author = {Tumpach, Alice Barbara},
title = {Hyperkaehler structures on the cotangent bundle of the restricted grassmannian and on a natural complexification of the restricted grassmannian},
journal = {HAL},
volume = {2005},
number = {0},
year = {2005},
language = {en},
url = {http://dml.mathdoc.fr/item/hal-00022117}
}
Tumpach, Alice Barbara. Hyperkaehler structures on the cotangent bundle of the restricted grassmannian and on a natural complexification of the restricted grassmannian. HAL, Tome 2005 (2005) no. 0, . http://gdmltest.u-ga.fr/item/hal-00022117/