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第843行：
第843行： − A [[master equation]] can express the behaviour of an undirected growing network where, at each time step, a new node is added to the network, linked to an old node (randomly chosen and without preference). The initial network is formed by two nodes and two links between them at time <math>t = 2</math>, this configuration is necessary only to simplify further calculations, so at time <math>t = n</math> the network have <math>n</math> nodes and <math>n</math> links.+ − The master equation for this network is:+ − where <math>p(k,s,t)</math> is the probability to have the node <math>s</math> with degree <math>k</math> at time <math>t+1</math>, and <math>s</math> is the time step when this node was added to the network. Note that there are only two ways for an old node <math>s</math> to have <math>k</math> links at time <math>t+1</math>:+
→主方程法
===主方程法===
===主方程法===
[[主方程]]可以描述一个无向生长图的行为，每一个时间步长添加一个新节点，将其与一个已有节点相连（无偏好地随机选择）。在<math>t = 2</math>时刻，网络初始化为两个节点以及它们之间的两条边，这样的初始化是为了简化之后的计算。所以在<math>t = n</math>时刻，网络有<math>n</math>个节点和<math>n</math>条边。
这个网络的主方程是：
: <math>p(k,s,t+1) = \frac 1 t p(k-1,s,t) + \left(1 - \frac 1 t \right)p(k,s,t),</math>
: <math>p(k,s,t+1) = \frac 1 t p(k-1,s,t) + \left(1 - \frac 1 t \right)p(k,s,t),</math>
其中 <math>p(k,s,t)</math> 是 <math>t+1</math>时刻节点<math>s</math>的度为<math>k</math>的概率，<math>s</math>是这个时间步长内新添加到网络中的节点。is the probability to have the node <math>s</math> with degree <math>k</math> at time <math>t+1</math>, and <math>s</math> is the time step when this node was added to the network. Note that there are only two ways for an old node <math>s</math> to have <math>k</math> links at time <math>t+1</math>:
* The node <math>s</math> have degree <math>k-1</math> at time <math>t</math> and will be linked by the new node with probability <math>1/t</math>
* The node <math>s</math> have degree <math>k-1</math> at time <math>t</math> and will be linked by the new node with probability <math>1/t</math>