Classicalization in Derivatively Coupled Scalar Field Theories: A Feasibility Study

TL;DR

This study investigates whether classicalization can serve as a UV-completion mechanism in derivative scalar field theories by comparing scattering amplitudes and classical structure formation, finding results contrary to previous expectations.

Contribution

The paper provides a detailed comparison of scattering processes in classicalizing and non-classicalizing theories, challenging the viability of classicalization as a self-unitarization mechanism.

Findings

Ratios of scattering amplitudes decrease with energy in classicalizing theories

Classicalization does not enhance classical structure formation as expected

Results question the effectiveness of classicalization for UV-completion

Abstract

It has been suggested that a certain class of UV-incomplete quantum field theories can avoid unitarity violation above the cut-off energy scale by forming classical configurations at a length scale much larger than the cut-off length. This phenomenon has been named classicalization and is characterized by a length scale called classicalization radius $r_*$ which increases with energy. It has been argued that scalar field theories with derivative self-interactions are likely candidate for UV-completetion by classicalization and are much likely to form classicalons compared to non-classicalizing theories like $\phi^4$ scalar field theory. To look further into this claim, in this paper 2 to N particle scattering amplitude, scattering cross-section and the amplitude of classical structure formation has been calculated and compared for a classicalizing and non-classicalizing theory. As the phenomenon of classicalization relies on creating a large number of low energy particles from high energy two particle scattering, the ratios between the scattering amplitudes and the amplitude of classical structure formation in these two cases are an indicator of the feasibility of the classicalization process. From our calculation, it has been observed that with the increase of energy, the ratios of the relevant quantities between classicalizing and non-classicalizing theory actually decrease which is quite contrary to the expected behaviour if classicalization is supposed to self-unitarize certain class of theories beyond cut-off energy.