Heterotic Quotes

The BEH mechanism operates within the context of gauge theories. Despite the fact that grand unification schemes reach scales comparable to the Planck scale, there was, a priori, no indication that Yang-Mills fields offer any insight into quantum gravity. The only approach to quantum gravity that had some success, in particular in the context of a quantum interpretation of the black hole entropies, are the superstring theory approaches and the possible merging of the five perturbative approaches (Type IIA, IIB, Type I and the two heterotic strings) into an elusive M-theory whose classical limit would be 11-dimensional supergravity. (Francois Englert)