Bootstrapping Pions at Large $N$

Understand

We revisit from a modern bootstrap perspective the longstanding problem of solving QCD in the large $N$ limit.

• We derive universal bounds on the effective field theory of massless pions by imposing the full set of positivity constraints that follow from $2 \to 2$ scattering.
• Some features of our exclusion plots have intriguing connections with hadronic phenomenology.
• The exclusion boundary exhibits a sharp kink, raising the tantalizing scenario that large $N$ QCD may sit at this kink.