Revealing the phase transition behaviors of k-core percolation in random networks

The $k$-core percolation is a fundamental structural transition in complex networks. Through the analysis of the size jump behaviors of $k$-core in the evolution process of networks, we confirm that $k$-core percolation is continuous phase transition when $k=1,2$ while it is a hybrid first-order-second-order phase transition when $k\ge 3$. $2$-core percolation belongs to different universality class from that of $1$-core (giant component) percolation. The discontinuity of $k$-core percolation with $k\ge 3$ can be concluded from largest size jump of $k$-core which will not disappear in the thermodynamic limit while its continuous characteristic is reflected by second largest size jump which converges to zero in power law as $N\to \infty$. Furthermore, along with the previously known exponent $\beta=0.5$, we obtain a set of exponents which are independent of $k$ when $k\ge 3$ and also different from those critical exponents of $1$-core and $2$-core percolation.