Particle Physics Seminar: The non-perturbative S-matrix, from analytics to numerical bootstrap

Zoom: https://zoom.us/j/97305349275?pwd=a3hoWWtscnJGRVJLNTZSaHYySEg3Zz09

Abstract:

We revisit analytical methods for constraining the nonperturbative S-matrix of unitary, relativistic, gapped theories in d>2 spacetime dimensions. We assume extended analyticity of the two-to-two scattering amplitude and use it together with elastic unitarity to develop two natural expansions of the amplitude. One is the threshold (non-relativistic) expansion and the other is the large spin expansion. The two are related by the Froissart-Gribov inversion formula. When combined with crossing and a local bound on the discontinuity of the amplitude, this allows us to constrain scattering at finite energy and spin in terms of the low-energy parameters measured in the experiment. Finally, we discuss the modern numerical approach to the S-matrix bootstrap and how it can be improved based on the results of our analysis.

Seminar Organizers: Prof. Erez Etzion & Dr. Liron Barak