CLNS 98/1561 TeV Scale Superstring and Extra Dimensions

Utilizing the idea of extra large dimensions, it has been suggested that the gauge and gravity couplings uni cation can happen at a scale as low as 1 TeV. In this paper, we explore this possibility within string theory. In particular, we discuss how the proton decay bound can be satis ed in Type I string theory. The string picture also suggests di erent scenarios of gauge and gravitational couplings uni cation. The various scenarios are explicitly illustrated with a speci c 4-dimensional N = 1 supersymmetric chiral Type I string model with Pati-Salam-like gauge symmetry. We point out certain features that should be generic in other Type I strings.