We investigate the synchronization transition of the modified Kuramoto model where the oscillators form a scale-free network with degree exponent $\lambda$. An oscillator of degree $k_i$ is coupled to its neighboring oscillators with asymmetric and degree-dependent coupling in the form of $J{k}_i^{\eta -1}$. By invoking the mean-field approach, we find eight different synchronization transition behaviors depending on the values of $\eta$ and $\lambda$, and derive the critical exponents associated with the order parameter and the finite-size scaling in each case. The synchronization transition point $J_c$ is determined as being zero (finite) when $\eta >\lambda -2$ $(\eta <\lambda -2)$. The synchronization transition is also studied from the perspective of cluster formation of synchronized vertices. The cluster-size distribution and the largest cluster size as a function of the system size are derived for each case using the generating function technique. Our analytic results are confirmed by numerical simulations.

• Received 1 June 2006

DOI:https://doi.org/10.1103/PhysRevE.75.011104