During supernovae or nucleon star mergers there exist spatial regions with large magnetic field strengths. Does this affect processes on the elementary particle level, in particular weak decays? For instance the proton mass is increased and parity violation allows for additional form factors. As a simple test case we study the decay rate of charged pions in such an environment. This is carried out, combining a tree-level calculation with lattice QCD simulations. The results are somewhat surprising.
