The spectrum of GUT-like gauge-scalar models

TL;DR

This paper investigates the spectrum of GUT-like gauge-scalar models using a gauge-invariant perturbative approach, revealing that elementary particles do not accurately represent the low-energy spectrum and providing comprehensive spectral data.

Contribution

It offers the most detailed spectroscopy of a GUT-like model including all spin channels up to 2, supporting a gauge-invariant perturbative framework for BSM theories.

Findings

Elementary spectrum does not match low-energy spectrum

Comprehensive spectral data up to spin 2 provided

Supports gauge-invariant perturbative approach for BSM models

Abstract

Past lattice simulations tentatively suggested that the spectrum of observable particles in BSM theories is qualitatively different than perturbatively expected. The discrepancy can be traced back to nontrivial field-theoretical effects arising from the requirement of gauge invariance. A perturbative but gauge-invariant approach working directly with bound states (as proposed by Fr\"ohlich, Morchio and Strocchi) could provide a solution, by allowing composite-state effects to be treated within a perturbative framework. We consider a toy GUT-like theory -- SU(3) Yang-Mills coupled to a scalar `Higgs' in the fundamental representation -- and expand on previous work by providing the most comprehensive spectroscopy to date, including all channels up to spin 2. Our results strongly support the general conclusion that the elementary spectrum is not an adequate proxy for the low-energy spectrum of a GUT, and also suggest a possible analytical approach to BSM model-building via the Fr\"ohlich-Morchio-Strocchi approach.