Constraints on Theories With Large Extra Dimensions

TL;DR

This paper investigates the viability of theories with large extra dimensions and a TeV-scale fundamental theory within M theory brane-worlds. It develops a framework to fix moduli, examining non-supersymmetric and supersymmetric bulk scenarios, and derives stabilization conditions and flux requirements, finding that non-SUSY cases demand extremely large fluxes while certain SUSY-bulk configurations (notably $n=5$ large dimensions with $M\sim 10$ TeV) can stabilize the radius with moderate flux and yield a radial dilaton potentially detectable in precision gravity experiments. It analyzes flavor, CP, and precision electroweak constraints, showing that higher-dimension operators impose lower bounds on the effective scale $M/g$ of roughly $6$–$10$ TeV, with CP-violating processes often pushing the bound higher unless additional flavor structures are invoked. Cosmological considerations emphasize the need for the bulk moduli to be in their ground state at early times, the tight reheating constraints, and the substantial challenges of two large dimensions; overall, the authors argue that models with many large dimensions and a $10$ TeV-scale fundamental theory are the most plausible and testable, while brane-world inflation and quintessence remain fertile areas for future work.

Abstract

Recently, a number of authors have challenged the conventional assumption that the string scale, Planck mass, and unification scale are roughly comparable. It has been suggested that the string scale could be as low as a TeV. In this note, we explore constraints on these scenarios. We argue that the most plausible cases have a fundamental scale of at least 10 TeV and five dimensions of inverse size 10 MeV. We show that a radial dilaton mass in the range of proposed millimeter scale gravitational arises naturally in these scenarios. Most other scenarios require huge values of flux and may not be realizable in M Theory. Existing precision experiments put a conservative lower bound of 6-10 TeV on the fundamental energy scale. We note that large dimensions with bulk supersymmetry might be a natural framework for quintessence, and make some other tentative remarks about cosmology.