(color online) (a) C(ω) at and for a series of αʼs. From top to bottom, α = 0.39, 0.385, 0.38, 0.375, and 0.37 (solid lines), and α = 0.395, 0.40, 0.405, and 0.41 (dashed lines). (b) The maximum value of C(ω) as functions of α for a series of ε. From top to bottom, ε = 0.0, , , , , , and . s = 0.8, Δ = 0.1. NRG parameters are Λ = 2.0, , and .