Editing Network theory (section)

== Spread ==
Content in a [[complex network]] can spread via two major methods: conserved spread and non-conserved spread.<ref>{{cite book | veditors = Newman M, Barabási AL, Watts DJ | date = 2006 | title = The Structure and Dynamics of Networks. | location = Princeton, N.J. | publisher = Princeton University Press }}</ref>  In conserved spread, the total amount of content that enters a complex network remains constant as it passes through.  The model of conserved spread can best be represented by a pitcher containing a fixed amount of water being poured into a series of funnels connected by tubes.  Here, the pitcher represents the original source and the water is the content being spread.  The funnels and connecting tubing represent the nodes and the connections between nodes, respectively.  As the water passes from one funnel into another, the water disappears instantly from the funnel that was previously exposed to the water.  In non-conserved spread, the amount of content changes as it enters and passes through a complex network.  The model of non-conserved spread can best be represented by a continuously running faucet running through a series of funnels connected by tubes.  Here, the amount of water from the original source is infinite. Also, any funnels that have been exposed to the water continue to experience the water even as it passes into successive funnels.  The non-conserved model is the most suitable for explaining the transmission of most [[infectious diseases]], neural excitation, information and rumors, etc.

===Network immunization===
The question of how to immunize efficiently scale free networks which represent realistic networks such as the Internet and social networks has been studied extensively. One such strategy is to immunize the largest  degree nodes, i.e., targeted (intentional) attacks<ref name="Callaway">{{cite journal | vauthors = Callaway DS, Newman ME, Strogatz SH, Watts DJ | title = Network robustness and fragility: percolation on random graphs | journal = Physical Review Letters | volume = 85 | issue = 25 | pages = 5468–5471 | date = December 2000 | pmid = 11136023 | doi = 10.1103/PhysRevLett.85.5468 | bibcode = 2000PhRvL..85.5468C | arxiv = cond-mat/0007300 | s2cid = 2325768 }}</ref> since for this case <math>pc</math> is relatively high and fewer nodes are needed to be immunized. 
However, in most realistic networks the global structure is not available and the  largest degree nodes are unknown.