Invited Lecture – Dr. Anastasios Giovanidis (Sorbonne University, France)

On Monday, January 17, at 6pm, our MSc programme will have the pleasure and honor of hosting online Dr. Anastasios Giovanidis, Permanent Researcher of the French National Center for Scientific Research, currently affiliated with the Sorbonne University, LIP6 lab, who will give an invited lecture on “Ranking Online Social Users by their Influence”.

When: Monday, Jan 17, 2022 18.00
DWS Master Program announcement link:
Zoom Link:

Abstract: In this talk I will present an original mathematical model to analyse the diffusion of posts within a generic online social platform. The main novelty is that each user is not simply considered as a node on the social graph, but is further equipped with his/her own Wall and Newsfeed, and has his/her own individual self-posting and re-posting activity. The influence probabilities to find posts from a given user on the Wall and Newsfeed of any other are derived in closed form as the solution of a linear system of equations. Using the solution, a new measure of per-user influence over the entire network can be defined, the Ψ-score. This score combines the user position on the graph with the user (re-)posting activity. In the homogeneous case where all users have the same activity rates, it is proved that the Ψ-score is equal to PageRank. An iterative algorithm to derive the new score for large graphs will be presented. The Ψ-score is compared against the empirical influence measured from very large data traces (Twitter, Weibo) and the results illustrate that it can accurately rank influencers with asymmetric (re-)posting activity for real world platforms.

Bio: Anastasios Giovanidis is a permanent researcher of the French National Center for Scientific Research (CNRS) since 2013, currently affiliated with the Sorbonne University, LIP6 lab. He obtained the Dr.-Ing. degree from the Technical University of Berlin, Germany in 2010, and the Diploma degree in electrical and computer engineering from the National Technical University of Athens, Greece. Prior to joining Sorbonne University, Dr. Giovanidis held research positions with Telecom ParisTech, France, the National Institute for Research in Computer Science and Automation (INRIA), France, and the Zuse Institute Berlin (ZIB), Germany. His research interests are in the general area of social, content and wireless networks, applying methods from stochastic modelling, optimisation and machine learning. His work has been funded by the French ANR-Young Researcher grant. Dr. Giovanidis has served as the general chair of WIOPT’17, and GameNets’19.