The d=6, N=1 heterotic string does not "live" in six dimensions
arXiv:hep-th/0110025
Abstract
We discuss why the N_6=1 heterotic string has to be viewed as something similar to a ``non-compact orbifold''. Only the perturbative spectrum is forced to satisfy the constraints imposed by the vanishing of six-dimensional anomalies. These do not apply to the states of the non-perturbative spectrum, such as those appearing when small instantons shrink to zero size.
7 pages, Latex, no figures, extended version of a work presented at "Modern Trends in String Theory, Lisbon, 13-17 July 2001