Seeking the Ground State of String Theory

Recently, a number of authors have challenged the conventional assumptionthat the string scale, Planck mass, and unification scale are roughlycomparable. It has been suggested that the string scale could be as low as aTeV. The greatest obstacle to developing a string phenomenology is our lack ofunderstanding of the ground state. We explain why the dynamics which determinesthis state is not likely to be accessible to any systematic approximation. Wenote that the racetrack scheme, often cited as a counterexample, suffers fromsimilar difficulties. We stress that the weakness of the gauge couplings, thegauge hierarchy, and coupling unification suggest that it may be possible toextract some information in a systematic approximation. We review the ideas ofKahler stabilization, an attempt to reconcile these facts. We consider whetherthe system is likely to sit at extremes of the moduli space, as in recentproposals for a low string scale. Finally we discuss the idea of MaximallyEnhanced Symmetry, a hypothesis which is technically natural, compatible withbasic facts about cosmology, and potentially predictive.Comment: 22 pp. latex. Invited talk presented at Yukawa-Nishinomiya symposium. Minor correction