ABSTRACT
Beyond the Desert 1999: Accelerator, Non-Accelerator and Space Approaches into the Next Millennium 373
Centre de Physique Theorique (CNRS UMR 7644), Ecole Poly technique, F-91128 Palaiseau Cedex, France
Abstract. Large extra dimensions, of size of order of TeV-1 ~ 10-16 cm, arise naturally in the context of supersymmetry breaking in string theory, while strings at a Te V scale offer a solution to the gauge hierarchy problem, as an alternative to softly broken supersymmetry or technicolor. In this short review, we present consistent perturbative realizations of string theories with large volume compactifications and low string tensions, and discuss their main physical implications,
Since the discovery that superstring theory was providing an ultraviolet regulator of quantum gravity, it has been customary to associate it with sub-Planckian physics, far out of reach of laboratory experiments, This expectation is natural in the conventional supersymmetric unification scenario at mGUT ~ 3 x 1016 Ge V, and met in the phenomenologically most promising weakly coupled heterotic string theory, which gives a qualitative description thereof, Despite this success, there are some physical motivations suggesting that large volume compactifications may be relevant for physics. One comes from the quantitative description of the gauge coupling unification which is off by roughly two orders of magnitude. Another results from the problem of supersymmetry breaking in string theory that requires a compactification scale of the order of a few Te V [1 J. This is one
of the very few general predictions of (perturbative) string theory, which relates the supersymmetry breaking scale to the size of internal compact dimensions [2].
