Andreas Ruffing , Thomas Deck , Martin Schlichenmaier 
String branchings on complex tori and algebraic representations
of generalized Krichever-Novikov algebras
(27K, amstex)

ABSTRACT.  The propagation
differential for bosonic strings on a complex torus
with three symmetric punctures is investigated. We study
deformation aspects between two point  and three point differentials
as well  as the behaviour of the corresponding
Krichever-Novikov algebras.
The structure constants are calculated and from this we derive a
central extension of the Krichever-Novikov algebras by means
of b-c systems.
The defining cocycle for this central extension deforms to
the well known Virasoro cocycle for certain kinds of
degenerations of the torus.
AMS subject classification (1991).:
17B66, 17B90, 14H52, 30F30, 81T40