New fermionic soft theorems

Understand

Soft limits of massless S-matrix are known to reflect symmetries of the theory.

• In particular for theories with Goldstone bosons, the double-soft limit of scalars reveals the coset structure of the vacuum manifold.
• In this letter, we propose that such universal double-soft behavior is not only true for scalars, but also for spin-1/2 particles in four dimensions and fermions in three dimensions.
• We first consider Akulov-Volkov theory, and demonstrate the double soft-limit of goldstinos yields the supersymmetry algebra.