On cosmologically induced hierarchies in string theory

TL;DR

This paper presents a cosmological mechanism within string theory that naturally creates a large hierarchy between the Planck scale and the string scale, while keeping gauge and Yukawa couplings constant over time.

Contribution

It introduces a perturbative string theory model demonstrating how cosmological evolution can produce a large hierarchy without varying fundamental couplings.

Findings

Large hierarchy between Planck and string scales achieved

Gauge and Yukawa couplings remain time-independent

Internal space and string coupling evolution compensate each other

Abstract

We propose, within a perturbative string theory example, a cosmological way to generate a large hierarchy between the observed Planck mass and the fundamental string scale. Time evolution results in three large space dimensions, one additional dimension transverse to our world and five small internal dimensions with a very slow time evolution. The evolution of the string coupling and internal space generate a large Planck mass. However due to an exact compensation between the time evolution of the internal space and that of the string coupling, the gauge and Yukawa couplings on our Universe are time independent.