Over the past three years our views on how the standard model of particle theory could be embedded into string theory have changed dramatically. The heterotic string is no longer the only possibility for such an embedding and other perturbative (or non-perturbative) corners of M-theory, like type I or II strings, now seem possible. It has also been realized that the string scale Ms is not necessarily close to the Planck scale and could be much smaller, of the order of the intermediate scale (MW Mp )1/2 , or even close to the weak scale. In addition, semi-realistic three-generation models have recently been constructed starting with type IIB compact orientifolds. I briefly discuss all of these developments which represent a revolution in our understanding of string phenomenology.
Classical and Quantum Gravity
- Pub Date:
- March 2000
- High Energy Physics - Phenomenology;
- High Energy Physics - Theory
- 15 pages, Latex file, no figures. Contribution to the proceedings of Strings 99, Potsdam (Germany), July 1999