The orientation-preserving diffeomorphism group of the circle, Diff(S1) admits a central extension called the Virasoro group. Its complexified Lie algebra is spanned by {Li}i in Z and c with Ln+L-n and c being real elements. c is called the central charge. The algebra satisfies
- [c,Ln]=0
- [Lm,Ln]=(n-m)Lm+n+c/12 (m3-m)δm,-n.
Note that the Virasoro algebra generates both a centrally extended orientation-preserving diffeomorphism group and a centrally extended orientation-preserving homeomorphism group of the circle. The difference lies in the topology chosen.
See also Kac-Moody algebra.
This article is a stub. You can help Wikipedia by fixing it.