TeV scale superstring and extra dimensions

Abstract

Utilizing the idea of extra large dimensions, it has been suggested that the gauge and gravity couplings unification can happen at a scale as low as 1 TeV. In this paper, we explore this phenomenological possibility within string theory. In particular, we discuss how the proton decay bound can be satisfied in Type I string theory. The string picture also suggests different scenarios of gauge and gravitational couplings unification. The various scenarios are explicitly illustrated with a specific 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.11.25.-w Typeset using REVT E X *

Branes and the gauge hierarchy

“…This possibility has a perturbative description within type-I string theory, which necessarily implies some submillimiter dimensions when the fundamental tension is near the TeV [5]. 1 Furthermore, explicit model building looks promising [9], while this radical proposal appears to be a priori compatible with all experimental constraints if the number of large transverse dimensions is larger than two, and marginally compatible if it is equal to two [10].…”

Brane mediated supersymmetry breaking

“…To illustrate these ideas we consider a toy model inspired by the work of Shiu and Tye [8] using intersecting D5-branes, where the intersection regions are effectively parallel D3-branes within a higher-dimensional spacetime. In this model two chiral families occur in the 4d intersection region at the origin fixed point (5 1 5 2 sector), with a third family on the D5 2 -brane (5 2 5 2 sector).…”

String balls at the LHC and beyond

“…An example of a typical value of g s in theories with large dimensions is g s = 2αv 2 /(2πl s ) 2 [7], where v 2 is the volume contained by the two small dimensions; if v 2 is a two-torus with radius equal to l s , then g s is between 0.2 and 0.02 depending on which α we choose. Of course, increasing the size of v 2 , we can geometrically dilute the value of α and accommodate larger values of g s .…”