Constrained Superfields in Dynamical Background
  We study the nonlinear realization of supersymmetry in a
dynamical/cosmological background in which derivative terms like kinetic terms
are finite. Starting from linearly realized theories, we integrate out heavy
modes without neglecting derivative terms to obtain algebraic constraints on
superfields. Thanks to the supersymmetry breaking contribution by the kinetic
energy, the validity of constrained superfields can be extended to cosmological
regimes and phenomena such as reheating after inflation, kinetic-energy
domination, and the kinetic and standard misalignment of axion.
