8,643 research outputs found
Random Information Spread in Networks
Let G=(V,E) be an undirected loopless graph with possible parallel edges and
s and t be two vertices of G. Assume that vertex s is labelled at the initial
time step and that every labelled vertex copies its labelling to neighbouring
vertices along edges with one labelled endpoint independently with probability
p in one time step. In this paper, we establish the equivalence between the
expected s-t first arrival time of the above spread process and the notion of
the stochastic shortest s-t path. Moreover, we give a short discussion of
analytical results on special graphs including the complete graph and s-t
series-parallel graphs. Finally, we propose some lower bounds for the expected
s-t first arrival time.Comment: 17 pages, 1 figur
Sizing the length of complex networks
Among all characteristics exhibited by natural and man-made networks the
small-world phenomenon is surely the most relevant and popular. But despite its
significance, a reliable and comparable quantification of the question `how
small is a small-world network and how does it compare to others' has remained
a difficult challenge to answer. Here we establish a new synoptic
representation that allows for a complete and accurate interpretation of the
pathlength (and efficiency) of complex networks. We frame every network
individually, based on how its length deviates from the shortest and the
longest values it could possibly take. For that, we first had to uncover the
upper and the lower limits for the pathlength and efficiency, which indeed
depend on the specific number of nodes and links. These limits are given by
families of singular configurations that we name as ultra-short and ultra-long
networks. The representation here introduced frees network comparison from the
need to rely on the choice of reference graph models (e.g., random graphs and
ring lattices), a common practice that is prone to yield biased interpretations
as we show. Application to empirical examples of three categories (neural,
social and transportation) evidences that, while most real networks display a
pathlength comparable to that of random graphs, when contrasted against the
absolute boundaries, only the cortical connectomes prove to be ultra-short
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