Feynman rules for string field theories with discrete target space
Abstract
We derive a minimal set of Feynman rules for the loop amplitudes in unitary models of closed strings, whose target space is a simply laced (extended) Dynkin diagram. The string field Feynman graphs are composed of propagators, vertices (including tadpoles) of all topologies, and leg factors for the macroscopic loops. A vertex of given topology factorizes into a fusion coefficient for the matter fields and an intersection number associated with the corresponding punctured surface. As illustration we obtain explicit expressions for the genus-one tadpole and the genus-zero four-loop amplitude.
Cite
@article{arxiv.hep-th/9506022,
title = {Feynman rules for string field theories with discrete target space},
author = {Saburo Higuchi and Ivan K. Kostov},
journal= {arXiv preprint arXiv:hep-th/9506022},
year = {2009}
}
Comments
19 pages, harvmac, 4 uuencoded figures included using epsf. A missing term added to the expression for the genus-one tadpole and Fig.3 modified correspondingly