Title: From Positivity to Gravity: Constraints on Massive Higher Spins. 

Host: Csaba Csaki

Abstract: In this talk, I will explore how causality constraints on scattering amplitudes — known as positivity bounds — impose powerful restrictions on the Effective Field Theory (EFT) of massive higher-spin particles. Focusing on spin-3/2 as a case study, which lies at the interface between low- and high-spin fields, I will show how consistency conditions necessitate the emergence of gravity, and how these constraints connect to swampland conjectures. I will also discuss additional nontrivial bounds that arise in the rigid limit, where gravity is decoupled, further constraining the EFT landscape for spin-1/2 particles.