On the discontinuity of the specific heat of the Ising model on a scale-free network

We consider the Ising model on an annealed scale-free network with node-degree distribution characterized by a power-law decay P(K)∼ K-λ. It is well established that the model is characterized by classical mean-field exponents for λ > 5. In this note we show that the specific-heat discontinuity δc_h at the critical point remains λ-dependent even for λ > 5: δch=3(λ-5)(λ-1)/[2(λ-3)^2] and attains its mean-field value δch=3/2 only in the limit λ → ∞. We compare this behaviour with recent measurements of the d dependency of δch made for the Ising model on lattices with d > 4.