Radius Stabilization and Anomaly-Mediated Supersymmetry Breaking

TL;DR

This paper presents a detailed 5D brane-world model where radius stabilization is achieved through gaugino condensation, enabling anomaly-mediated supersymmetry breaking without fine-tuning, and clarifies the absence of certain contact terms.

Contribution

It demonstrates a natural radius stabilization mechanism in a 5D brane setup that supports anomaly-mediated supersymmetry breaking, resolving issues with contact terms and modulus runaway behavior.

Findings

Radius is stabilized by gaugino condensation in bulk and brane sectors.

Supersymmetry breaking is communicated mainly via anomaly mediation.

No fine-tuning needed beyond cosmological constant adjustment.

Abstract

We analyze in detail a specific 5-dimensional realization of a "brane-universe" scenario where the visible and hidden sectors are localized on spatially separated 3-branes coupled only by supergravity, with supersymmetry breaking originating in the hidden sector. Although general power counting allows order 1/M_{Planck}^2 contact terms between the two sectors in the 4-dimensional theory from exchange of supergravity Kaluza-Klein modes, we show that they are not present by carefully matching to the 5-dimensional theory. We also find that the radius modulus corresponding to the size of the compactified dimension must be stabilized by additional dynamics in order to avoid run-away behavior after supersymmetry breaking and to understand the communication of supersymmetry breaking. We stabilize the radius by adding two pure Yang--Mills sectors, one in the bulk and the other localized on a brane. Gaugino condensation in the 4-dimensional effective theory generates a superpotential that can naturally fix the radius at a sufficiently large value that supersymmetry breaking is communicated dominantly by the recently-discovered mechanism of anomaly mediation. The mass of the radius modulus is large compared to m_{3/2}. The stabilization mechanism requires only parameters of order one at the fundamental scale, with no fine-tuning except for the cosmological constant.