Hebbar, AdityaKarateev, DenisPenedones, Joao2022-01-312022-01-312022-01-312022-01-1310.1007/JHEP01(2022)060https://infoscience.epfl.ch/handle/20.500.14299/184885WOS:000742649500006We 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.Physics, Particles & FieldsPhysicsfield theories in higher dimensionsnonperturbative effectsscattering amplitudescrossing relationsanalytic propertiestext::journal::journal article::research article