The restricted Siegel disc as coadjoint orbit

Abstract

The restricted Siegel disc is a homogeneous space related to the connected component $T_0(1)$ of the Universal Teichmüller space via the period mapping. In this paper we show that it is a coadjoint orbit of the universal central extension of the restricted symplectic group or, equivalently, an affine coadjoint orbit of the restricted symplectic group with cocycle given by the Schwinger term.

16 pages