Lorentz Violation from the Higgs Portal

TL;DR

This paper investigates how Lorentz invariance can be broken in the Higgs sector due to coupling with a hidden sector, leading to observable effects on particle speeds and interactions, with implications for Standard Model physics.

Contribution

It introduces a low-energy effective framework for Lorentz violation originating from the Higgs portal, including calculations of particle speed modifications and their renormalization group evolution.

Findings

Higgs speed-of-light can be smaller than c due to inhomogeneous vacuum expectation values.

Lorentz violation effects are transmitted to fermions and gauge bosons, notably through loop diagrams.

Strong interactions tend to equalize the speeds of all colored particles.

Abstract

We study bounds and signatures of models where the Higgs doublet has an inhomo- geneous mass or vacuum expectation value, being coupled to a hidden sector that breaks Lorentz invariance. This physics is best described by a low-energy effective Lagrangian in which the Higgs speed-of-light is smaller than c; such effect is naturally small because it is suppressed by four powers of the inhomogeneity scale. The Lorentz violation in the Higgs sector is communicated at tree level to fermions (via Yukawa interactions) and to massive gauge bosons, although the most important effect comes from one-loop dia- grams for photons and from two-loop diagrams for fermions. We calculate these effects by deriving the renormalization-group equations for the speed-of-light of the Standard Model particles. An interesting feature is that the strong coupling dynamically makes the speed-of-light equal for all colored particles.