On the stability of a soft-wall model

TL;DR

This paper analyzes the stability and fluctuations of a soft-wall model with an asymptotically AdS metric, showing how it can generate a hierarchy between the weak and Planck scales and exploring implications for particle spectra and unparticles.

Contribution

It introduces a soft wall model with specific boundary conditions that fix the mass scale and produce a non-massless radion, offering new insights into hierarchy generation and unparticle physics.

Findings

Radion acquires mass due to boundary conditions.

Hierarchy between weak and Planck scales can be achieved.

Potential unparticle solutions to the hierarchy problem.

Abstract

We investigate the stability and fluctuations of a soft wall model that has an asymptotically AdS metric and a scalar field that has an asymptotically power-law dependence in the conformal coordinate. By imposing UV boundary conditions, the soft wall mass scale can be fixed to be near the TeV scale and causes the radion to no longer be massless. A hierarchy between the weak scale and the Planck scale can be generated for various particle spectrum behavior, although natural values only occur for a gravitational sector containing scalar fields that act like unparticles. In addition, if bulk Standard Model fields have nonstandard couplings to the gravitational sector, then a discrete particle spectrum can be realized in the nongravitational sector. This allows for the possibility of an unparticle solution to the hierarchy problem.