Abstract: For this journal club meeting I will comment on a recent paper by Albert and Rastelli (https://arxiv.org/abs/2203.11950) in which they apply modern S-matrix bootstrap techniques to the old problem of solving QCD in the large N limit. In particular, they derive universal bounds for the EFT of massless pions and find that the allowed region for large N theories compatible with unitarity, causality and analiticity of the S-matrix exhibits a sharp kink, suggesting the possibility that large N QCD might sit on it in a similar way as the 3D Ising model.
Finally, I will make some remarks on the similitudes and differences between this case and that of obtaining bounds for the gravitational S-matrix, and on the difficulties in extending this ideas to the latter.
