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Large very dense subgraphs in a stream of edges

Published online by Cambridge University Press:  25 January 2022

Claire Mathieu
Affiliation:
CNRS and IRIF, Paris, France
Michel de Rougemont*
Affiliation:
University Paris II and IRIF, Paris, France
*
*Corresponding author. Email: mdr@irif.fr
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Abstract

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We study the detection and the reconstruction of a large very dense subgraph in a social graph with n nodes and m edges given as a stream of edges, when the graph follows a power law degree distribution, in the regime when $m=O(n. \log n)$. A subgraph S is very dense if it has $\Omega(|S|^2)$ edges. We uniformly sample the edges with a Reservoir of size $k=O(\sqrt{n}.\log n)$. Our detection algorithm checks whether the Reservoir has a giant component. We show that if the graph contains a very dense subgraph of size $\Omega(\sqrt{n})$, then the detection algorithm is almost surely correct. On the other hand, a random graph that follows a power law degree distribution almost surely has no large very dense subgraph, and the detection algorithm is almost surely correct. We define a new model of random graphs which follow a power law degree distribution and have large very dense subgraphs. We then show that on this class of random graphs we can reconstruct a good approximation of the very dense subgraph with high probability. We generalize these results to dynamic graphs defined by sliding windows in a stream of edges.

Information

Type
Research Article
Copyright
© The Author(s), 2022. Published by Cambridge University Press