The spacing of nearest levels of the spectrum of a complex network can be
regarded as a time series. Joint use of Multi-fractal Detrended Fluctuation
Approach (MF-DFA) and Diffusion Entropy (DE) is employed to extract
characteristics from this time series. For the WS (Watts and Strogatz)
small-world model, there exist a critical point at rewiring probability . For a
network generated in the range, the correlation exponent is in the range of .
Above this critical point, all the networks behave similar with that at . For
the ER model, the time series behaves like FBM (fractional Brownian motion)
noise at . For the GRN (growing random network) model, the values of the
long-range correlation exponent are in the range of . For most of the GRN
networks the PDF of a constructed time series obeys a Gaussian form. In the
joint use of MF-DFA and DE, the shuffling procedure in DE is essential to
obtain a reliable result. PACS number(s): 89.75.-k, 05.45.-a, 02.60.-xComment: 10 pages, 9 figures, to appear in PR