When Effective Field Theories Fail

TL;DR

This paper critically examines the limitations of effective field theories across different domains, highlighting specific cases where standard assumptions break down and proposing lessons for future theoretical developments.

Contribution

It presents four non-standard claims about effective field theories, challenging conventional assumptions and suggesting new directions for understanding their limitations.

Findings

Kaon loops are unreliable in chiral perturbation theory

Regge physics is missing from SCET due to scale issues

Infrared barriers may limit EFT use in general relativity

Abstract

In this talk, I describe and defend four non-standard claims about four effective field theories, and try to extract some lessons about the limits of effective field theory. The four theses (and a capsule diagnosis given in parentheses) are: 1) Kaon loops are not a reliable part of chiral perturbation theory (dimensional regularization does not know about the chiral scale), 2) Regge physics is inappropriately missing from SCET (an infinite set of scales are needed) 3) There is likely a barrier in the use of EFT in general relativity in the extreme infrared (curvature effects build up) and 4) Gauge non-invariant operators should be included in describing physics beyond the Standard Model (as they could probe the idea of emergent gauge symmetry and falsify string theory).