|Talks|

The power law hypothesis and local weak convergence for PageRank

Misinformation Speaker Series
In-person
Past Talk
Nelly Litvak
Mar 21, 2025
3:00 pm
EST
Mar 21, 2025
3:00 pm
In-person
Portsoken Street
London, E1 8PH, UK
The Roux Institute
Room
100 Fore Street
Portland, ME 04101
Network Science Institute
2nd floor
Network Science Institute
11th floor
177 Huntington Ave
Boston, MA 02115
Network Science Institute
2nd floor
Room
58 St Katharine's Way
London E1W 1LP, UK
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Talk recording

PageRank, introduced by Google in 1998 to rank web pages, is one of most common centrality measures in complex networks. In the empirical data, whenever a network, directed or undirected, has a power law (in-)degree distribution, PageRank follows the power law with the same exponent. The so-called power law hypothesis conjectures that this observation holds for all networks with power-law (in-)degree distribution. In this talk I will tell about the exploration of the power law hypothesis in random graph models. An important ingredient of the recent analysis is the local weak convergence of sparse random graphs. The local weak convergence formally describes what the graph looks like locally, at a finite distance of a randomly chosen vertex. While the local weak convergence in itself doesn’t say anything about power laws, it has facilitated a major leap forward in resolving the power law hypothesis. In particular, there is an unexpected striking difference of PageRank properties in directed versus undirected networks.

About the speaker
Nelly Litvak has received her PhD in applied probability from Eindhoven University of Technology (TU/e). After that she was an assistant, associate and full professor at the University of Twente. From 2023, she returned to the TU/e as a full professor. Her research is on complex networks and random graphs with applications to web analytics, social networks and pandemic preparedness. Nelly has received many grants and awards including the Stieltjes prize for the best PhD thesis and the Teacher of the Year award from the University of Twente in 2022. This talk is supported by the National Science Foundation (NSF) under Grant No.\ DMS-1928930 while Nelly is in residence as research professor at the Simons Laufer Mathematical Sciences Institute at UC Berkeley during the Spring 2025 semester.
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Mar 21, 2025