Brane to bulk supersymmetry breaking and radion force at micron distances

TL;DR

This work analyzes how brane-localized SUSY breaking in type I string models with large extra dimensions mediates to the bulk. By computing one-loop corrections to bulk scalar and gravitino masses and deriving the radion’s couplings, it shows that scalar bulk fields acquire masses of order $M_s^2/M_P$ while gravitinos are typically heavier, of order $1/R$, due to Scherk–Schwarz boundary conditions. The radion, with mass around $M_s^2/M_P$, mediates a universal attractive force at micron distances, potentially detectable in microgravity experiments, and in the two-large-dimensions scenario a one-loop radion potential can stabilize the radius, yielding the desired hierarchy between the string and Planck scales. The results provide a concrete framework for brane-to-bulk mediation and connect short-distance gravity tests to string-scale physics. This work thus links radion phenomenology, extra-dimensional stabilization, and SUSY-breaking mediation within a calculable string-theoretic setting.

Abstract

We study mediation of supersymmetry breaking in the bulk, in models with primordial supersymmetry breaking on D-branes at the string scale, in the TeV region. We compute the gravitino and scalar masses up to one-loop level, as well as the radion coupling to matter. We find that the latter mediates a model independent force at submillimeter distances that can be tested in micro-gravity experiments for any dimensionality of the bulk. In the case of two large dimensions, our type I string framework provides an example which allows to stabilize the radion potential and determine the desired hierarchy between the string and Planck scales.

Figures (4)

• Figure 1: Present limits on non-Newtonian forces at short distances (gray regions), compared to new forces mediated by the graviton in the case of two large extra dimensions, and by the radion.
• Figure 2: The supersymmetric, non-supersymmetric and mixed models. The dotted lines denote directions along which non-periodic boundary conditions are imposed on the bulk fermions. The plain (dotted) disks stand for locations of supersymmetric (non-supersymmetric) branes.
• Figure 3: The string scale as a function of the coupling constant for different choices for the number of non-supersymmetric branes.
• Figure 4: The one-loop self-energy localized on the boundary introduces a mixing between the KK states and modifies the mass spectrum.