(color online) NRG flow diagrams and C(ω) at s = 0.3, Δ = 0.1, . (solid lines) and (dashed lines). (a) Flow diagrams obtained using , 27, and 60 (from left to right). The horizontal dashed lines are the flow of α = 0 and ε = 0. (b) C(ω) for , 27, and 60 (from bottom to top). The functions and are marked by the dashed straight lines for guiding the eye. The peak is not shown. NRG parameters are Λ = 4.0 and .