Bound states in Functional Renormalization Group

Understand

Equivalence criteria are established for an effective Yukawa-type theory of composite fields representing two-particle fermion bound states with the original "microscopic" theory of interacting fermions based on the spectral decomposition of the 2-to-2 fermion scattering amplitude.

• Functional renormalisation group equations of the effective theory are derived exploiting relations expressing the equivalence.
• The effect of truncating the spectral decomposition is investigated quantitatively on the example of the non-relativistic bound states of two oppositely charged fermi particles.