Self-energy feedback and frequency-dependent interactions in the   functional renormalization group flow for the two-dimensional Hubbard model
  We study the impact of including the self-energy feedback and frequency-dependent interactions on functional renormalization group grows for the two-dimensional Hubbard model on the square lattice at weak to moderate coupling strength. Previous studies using the functional renormalization group had ignored these two ingredients to large extent, and the question is how much the flows to strong coupling analyzed by this method depend on these approximations. Here we include the imaginary part of the self-energy on the imaginary axis and the frequency-dependence of the running interactions on a frequency mesh of 10 frequencies on the Matsubara axis. We find that i) the critical scales for the flows to strong coupling are shifted downwards by a factor that is usually of order one but can get larger in specific parameter regions, and ii) that the leading channel in this flow does not depend strongly on whether self-energies and frequency-dependence is included or not. We also discuss the main features of the self-energies developing during the flows. 
Stefan Uebelacker, Carsten Honerkamp
cond-mat.str-el