Dresden 2011 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 19: Networks: From Topology to Dynamics II (with BP, SOE)

DY 19.6: Vortrag

Mittwoch, 16. März 2011, 12:15–12:30, GÖR 226

Are motifs a myth? — •Jörg Reichardt¹, Roberto Alamino², and David Saad² — ¹Complexity Sciences Center, UC Davis and Würzburg University — ²Aston University, Birmingham

Small subgraphs, called network motifs, have received considerable attention in network research over the last years and are suggested as simple building blocks of complex networks. Motifs are attributed functional significance due to their strong over- or underrepresentation when compared to random null models. However, the link randomized null models used for such comparisons generally match the observed networks only in terms of their microscopic structure, destroying all mesoscopic features and hence give biased estimates of the statistical significance of motif counts in real world networks.

We present a generative probabilistic model based on Exponential Random Graphs plus an algorithm to infer model parameters from a given network. This model allows to generate an ensemble of random null models that matches the observed network with respect to both its microscopic and mesoscopic structural features.

We show that such random null models may result in a much more conservative estimation of the statistical significance of motif counts in real world networks. Further, they maintain the parsimonious explanation of complex networks as a collection of conditionally independent edges.