A Top Seesaw on a 5D Playground

TL;DR

This paper investigates quantum corrections in a 5D Yukawa theory with a compactified extra dimension, revealing symmetry-breaking vacuum solutions and brane-localized terms, with implications for top condensation and seesaw mechanisms.

Contribution

It demonstrates how boundary conditions and fermion loops influence chiral symmetry breaking and mass generation in a 5D framework, connecting to top condensation models.

Findings

Vacuum solutions break chiral symmetry due to fermion loops.

Quadratic divergences in scalar mass are absent at one loop.

The model supports a natural seesaw mechanism for top quark mass.

Abstract

We study quantum corrections to an extra dimensional Yukawa theory where a single flat extra spatial dimension is compactified on an interval. At a UV scale this theory can be made equivalent to a 5D theory with a bulk four-fermion operator by choosing appropriate boundary conditions for the running of the low-energy theory. Using the fermion bubble approximation we find vacuum solutions which break the chiral symmetries that arise from compactification. Of particular interest are the form of brane localized terms which arise from fermion loops. For example, quadratically divergent contributions to the scalar mass are absent at one loop due to a remnant of 5D Lorentz invariance that is only lost after introducing fermion bulk masses. The model is interpreted as an implementation of top condensation in extra dimensions with an automatic seesaw mechanism.