Metamorphosis versus Decoupling in Nonabelian Gauge Theories at Very High Energies

TL;DR

This paper explores the high-energy behavior of nonabelian gauge theories with zero mass limits, contrasting the metamorphosis of longitudinal modes in Higgs mechanisms with decoupling in nonlinear realizations, revealing implications for unitarity without a Higgs boson.

Contribution

It introduces a comparative analysis of two different massless limits in nonabelian gauge theories, highlighting their distinct high-energy behaviors and implications for unitarity.

Findings

Longitudinal modes metamorphose into Goldstone scalars in Higgs mechanism.

Decoupling occurs in nonlinear gauge realizations, associated with phase changes.

Presence of a massless Higgs doublet affects high-energy behavior.

Abstract

In the present paper we study the limit of zero mass in nonabelian gauge theories both with Higgs mechanism and in the nonlinear realization of the gauge group (Stueckelberg mass). We argue that in the first case the longitudinal modes undergo a metamorphosis process to the Goldstone scalar modes, while in the second we guess a decoupling process associated to a phase transformation. The two scenarios yield strikingly different behaviors at high energy, mainly ascribed to the presence of a massless Higgs doublet among the physical modes in the case of Higgs mechanism (i.e. not only the Higgs boson). The aim of this work is to show that the problem of unitarity at high energy in nonabelian gauge theory with no Higgs boson can open new perspectives in quantum field theory.