UV-Completion by Classicalization

TL;DR

The paper introduces classicalization as a non-Wilsonian UV-completion mechanism in which high-energy scattering is unitarized by producing extended classical configurations (classicalons) sourced by energy-momentum. It identifies two natural classicalizers—Nambu-Goldstone modes and Higgs-like scalars—and analyzes how the resulting r_* radius governs the transition to long-distance classical dynamics, yielding geometric cross sections and multi-particle final states. The authors apply this framework to the Standard Model, outlining Higgsless and Higgs-assisted routes, each predicting distinctive collider signatures and implications for electroweak observables. Through explicit scalar and vector toy models and non-Abelian generalizations, the work argues that classicalization could provide a self-contained, non-Wilsonian path to UV-completion with testable consequences at the LHC and connections to gravitational intuition.

Abstract

We suggest a novel approach to UV-completion of a class of non-renormalizable theories, according to which the high-energy scattering amplitudes get unitarized by production of extended classical objects (classicalons), playing a role analogous to black holes, in the case of non-gravitational theories. The key property of classicalization is the existence of a classicalizer field that couples to energy-momentum sources. Such localized sources are excited in high-energy scattering processes and lead to the formation of classicalons. Two kinds of natural classicalizers are Nambu-Goldstone bosons (or, equivalently, longitudinal polarizations of massive gauge fields) and scalars coupled to energy-momentum type sources. Classicalization has interesting phenomenological applications for the UV-completion of the Standard Model both with or without the Higgs. In the Higgless Standard Model the high-energy scattering amplitudes of longitudinal $W$-bosons self-unitarize via classicalization, without the help of any new weakly-coupled physics. Alternatively, in the presence of a Higgs boson, classicalization could explain the stabilization of the hierarchy. In both scenarios the high-energy scatterings are dominated by the formation of classicalons, which subsequently decay into many particle states. The experimental signatures at the LHC are quite distinctive, with sharp differences in the two cases.