Scaling properties of first-passage quantities on the fractal and   transfractal scale free networks
  In this paper, we consider the random walk process on a kind of fractal (or transfractal) scale free networks, which also called as $(u,v)$ flowers, and we focus on the global first passage time (GFPT) and first return time (FRT). Here, we present method to derive exactly the probability generation function, mean and variance of the GFPT and FRT for a given hub (i.e., node with the highest degree) and then the scaling properties of the mean and the variance of the GFPT and FRT are disclosed. Our results show that, for the case of $u>1$, while the networks are fractals, the mean of the GFPT scales with the volume of the network as $\langle GMFPT_t\rangle \sim N_t^{{2}/{d_s}}$, where $\langle * \rangle$ denotes the mean of random variable $*$, $N_t$ is the volume of the network with generation $t$ and $d_s$ is the spectral dimension of the network; but, for the case of $u=1$, while the networks are nonfractals, the mean of the GFPT scales as $\langle GMFPT_t\rangle \sim N_t^{{2}/{\tilde{d}_s}}$, where $\tilde{d}_s$ is the transspectral dimension of the network, which is introduced in this paper. Results also show that, the variance of the GFPT scales as $Var(GFPT_t) \sim \langle GFPT_{t}\rangle^2$, where $Var(*)$ denotes variance of of random variable $*$; whereas the variance of the FRT scales as $Var(FRT_t) \sim \langle FRT_{t} \rangle \langle GFPT_{t}\rangle$. %$Var(GFPT_t) \sim \langle GFPT_{t}\rangle^2$ and $Var(FRT_t) \sim \langle FRT_{t} \rangle \langle GFPT_{t}\rangle$, where $Var(GFPT_t)$ and $Var(FRT_t)$ denote the variance of the GFPT and the FRT, $\langle GFPT_{t}\rangle$ and $\langle FRT_{t}\rangle$ denote the mean of the GFPT and the FRT respectively. 
Junhao Peng
cond-mat.stat-mech nlin.CD