Snowmass White Paper: UV Constraints on IR Physics

TL;DR

This white paper surveys how fundamental UV principles—causality, unitarity, and analyticity—impose rigorous constraints on IR effective field theories, including SMEFT and gravitational EFTs, via dispersion relations, positivity bounds, and the EFT-Hedron framework. It extends these ideas to AdS/CFT, showing how dual CFT data constrain bulk gravity and higher-derivative interactions, and discusses how swampland conjectures (like the WGC and towers of states) can be probed with positivity bounds and holography. The work highlights concrete applications to particle physics and cosmology and outlines promising avenues—especially unifying flat-space and AdS results, pushing higher-point bootstrap, and encoding swampland insights into testable QFT predictions. Overall, it argues that UV consistency provides powerful, testable priors that sharpen our understanding of IR physics and guide searches for new phenomena.

Abstract

Fundamental principles of local quantum field theory or of quantum gravity can enforce consistency requirements on the space of consistent low-energy effective field theories. We survey the various techniques that have been used to put UV constraints on IR physics, including those from causality considerations in the form of S-matrix positivity and bootstrap bounds, scattering time delays, conformal field theory and holographic methods, together with those that arise from landscape/swampland criteria such as the weak gravity conjecture. We review recent applications of these constraints to corrections to Standard Model physics, corrections to Einstein gravity, and cosmological theories and highlight promising future directions.

Figures (1)

• Figure 1: 2-2 scattering amplitude