Spinning S-matrix Bootstrap in 4d

Understand

We review unitarity and crossing constraints on scattering amplitudes for particles with spin in four dimensional quantum field theories.

• As an application we study two to two scattering of neutral spin 1/2 fermions in detail.
• Assuming Mandelstam analyticity of its scattering amplitude, we use the numerical S-matrix bootstrap method to estimate various non-perturbative bounds on quartic and cubic (Yukawa) couplings.