GUTs and String-GUTs

Abstract

We look for a connection between string theories and Grand Unified Theories (GUTs), with the aim to look for new insights in the existing four dimensional string-GUT problems. We argue that the construction of consistent string-GUT models could require the use of non canonical affine levels. We list the most common level values related to realistic GUTs.

Comments: 8 pages, Latex file, no figures. Acepted for publication in Europhysics Letters