Connectedness of levels for moment maps on various classes of loop groups
Mare, Augustin-Liviu
Osaka J. Math., Tome 47 (2010) no. 1, p. 609-626 / Harvested from Project Euclid
The space $\Omega(G)$ of all based loops in a compact simply connected Lie group $G$ has an action of the maximal torus $T \subset G$ (by pointwise conjugation) and of the circle $S^{1}$ (by rotation of loops). Let $\mu\colon \Omega(G) \to (\mathfrak{t} \times i\mathbb{R})^{*}$ be a moment map of the resulting $T \times S^{1}$ action. We show that all levels (that is, pre-images of points) of $\mu$ are connected subspaces of $\Omega(G)$ (or empty). The result holds if in the definition of $\Omega(G)$ loops are of class $C^{\infty}$ or of any Sobolev class $H^{s}$, with $s \ge 1$ (for loops of class $H^{1}$ connectedness of regular levels has been proved by Harada, Holm, Jeffrey, and the author in [3]).
Publié le : 2010-09-15
Classification:  53D20,  22E67
@article{1285334468,
     author = {Mare, Augustin-Liviu},
     title = {Connectedness of levels for moment maps on various classes of loop groups},
     journal = {Osaka J. Math.},
     volume = {47},
     number = {1},
     year = {2010},
     pages = { 609-626},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1285334468}
}
Mare, Augustin-Liviu. Connectedness of levels for moment maps on various classes of loop groups. Osaka J. Math., Tome 47 (2010) no. 1, pp.  609-626. http://gdmltest.u-ga.fr/item/1285334468/