The Soft-Wall Standard Model

TL;DR

This paper investigates a soft-wall warped extra-dimensional model for electroweak physics, featuring a smooth dilaton cutoff, and demonstrates its potential to produce realistic fermion masses, gauge symmetry breaking, and Kaluza-Klein spectra compatible with experimental constraints.

Contribution

It introduces a soft-wall framework replacing the IR boundary with a dilaton field, enabling linear Regge trajectories and realistic fermion localization in electroweak models.

Findings

Discrete Kaluza-Klein spectrum with linear Regge behavior

Fermion localization via bulk Yukawa interactions

Electroweak models with reduced constraints allowing TeV-scale KK masses

Abstract

We explore the possibility of modeling electroweak physics in a warped extra dimension with a soft wall. The infrared boundary is replaced with a smoothly varying dilaton field that provides a dynamical spacetime cutoff. We analyze gravity, gauge fields, and fermions in the soft-wall background and obtain a discrete spectrum of Kaluza-Klein states which can exhibit linear Regge-like behavior. Bulk Yukawa interactions give rise to nonconstant fermion mass terms, leading to fermion localization in the soft-wall background and a possible explanation of the Standard Model flavor structure. Furthermore we construct electroweak models with custodial symmetry, where the gauge symmetry is broken with a bulk Higgs condensate. The electroweak constraints are not as stringent as in hard-wall models, allowing Kaluza-Klein masses of order the TeV scale.