Political Discourse on Social Media: Echo Chambers, Gatekeepers, and the Price of Bipartisanship. WWW 2018. [ACM][arXivWith K. Garimella, G. De Francisci Morales, A. Gionis. Covered on CNETLe Monde.

Tutorial: Polarization on Social Media. [slidesWWW 2018 and AAAI ICWSM 2017. With K. Garimella, G. De Francisci Morales, A. Gionis

Markov Chain MonitoringSDM 2018With Harshal Chauduri, Evimaria Terzi. [arXiv – full version]

Quantifying Controversy on Social Media. Springer Transactions on Social Computing 2017. With K. Garimella, G. De Francisci Morales, A. Gionis

Social Media Analysis. Encyclopedia of Database Systems. Thanks to Nick Koudas for the invitation.

The Effect of Collective Attention on Controversial Debates on Social Media. WebSci 2017. With K. Garimella, G. De Francisci Morales, A. Gionis. Best Student Paper. [Slides]

Reducing Controversy by Connecting Opposing Views. WSDM 2017. With K. Garimella, G. De Francisci Morales, A. Gionis. [ACM][SlidesBest Student Paper. Covered on Acolyer, Aalto News, Communications of ACM – News, Science Newsline, Slate.

Local Discrepancy Maximization on Graphs. TKDE 2017. [IEEEXploreWith A. Gionis, A. Ukkonen

Modeling Urban Behavior by Mining Urban Data. IEEE Transactions on Big Data / Special Issue on Urban Computing. With E. Çelikten, G. Le Falher. [IEEEXplore]

“What Is the City but the People?” Exploring Urban Activity Using Social Web Traces. Demo at WWW2016. With E. Çelikten, G. Le Falher.  [ACM] [pdf]

Absorbing random-walk centrality: Theory and algorithms. ICDM 2015. With A. Gionis, H. Mavroforakis. [Arxiv] [Slides] [Blog Post]

Detecting Prominent Patterns of Activity in Social Media, PhD Thesis, 2013
Advisor: Nick Koudas, Committee: Vassos Hadzilacos, Peter Marbach, Panos Ipeirotis.

Available on the UofT Library.

Sparsification of influence networks. Appeared at KDD 2011. With Francesco Bonchi, Carlos Castillo, Aristides Gionis, and Antti Ukkonen. [ACM][Code]

Other Publications available on Google Scholar and DBLP.


Professional Service
Reviewer or committee member for the following venues:

2019: ICDE, PVLDB.
2017: SIG KDD, WWW, ICWSM, ICDE, Information Retrieval (INRT), Workshop on Social News On the Web (SNOW), Data Science in Societal Debates (DSSD), IEEE Transactions on Big Data (TBD), IEEE DSAA, KnowME@PKDD.
2016: VLDB Journal, WWW, Transactions on Knowledge and Data Engineering (TKDE), Workshop on Social News On the Web (SNOW), Workshop on Social Media and Risk (SoMeRis), Transactions on Intelligent Systems and Technology, Transactions on Information Systems, ECML PKDD Journal (DAMI).
: VLDB Journal, ECML PKDD Journal (DAMI), CIKM, WWW, Internet Mathematics, Transactions on Information Systems (TOIS), Knowledge and Information Systems (KAIS).
2014: WWW, CIKM, ICWSM, Transactions on Parallel & Distributed Systems (TPDS), Transactions on Dependable and Secure Computing (TDSC).

Reviewer for the following PhD theses:

  • ‘Data Analytics for Urban Dynamics Understanding, Monitoring and Simulation’,
    PhD Candidate: Farzad Vaziri, University of Pisa,
    Supervisors: Prof. Dino Pedreschi, Dr. Mirco Nanni.

Reviewer for 2 Master’s Theses at University of Helsinki.


  • The Web Conference (WWW2018), April 2018, Tutorial ‘Polarization on social media’
  • Covve, Athens, Greece, July 2017, ‘A short tour of Machine Learning’
  • Intl. Workshop on Machine Learning for Large Scale Networks, Alaska, USA, May 2017,  ‘Polarization on Social Media’
  • Lyon I, Claude Bernard, May 2017, ‘Social Media Analysis’
  • INSA Lyon, May 2017 , ‘Social Media Analysis’
  • NYU Abu Dhabi, April 2017, ‘Polarization on Social Media’
  • London School of Economics, March 2017, ‘Polarization on Social Media’
  • Elisa, Helsinki, Finland, Dec. 2016, ‘Urban Computing’
  • Futurice, Dec.2016, ‘Expert Finding in Social Networks’
  • PyCon Finland, Nov. 2016, ‘Visualizing Twitter Discussions with NetworkX’
  • Sanoma, Dec. 2015, ‘Social Media Analysis’
  • Inria, Lille, France, May 2015, ‘Absorbing Random Walk Centrality’


Network Analysis, University of Helsinki, Spring 2019, with Ben Hui.
News and Media on the Web, Seminar, University of Helsinki, Fall 2019.
Introduction to Big Data Management: Semi-structured data and MongoDB, University of Helsinki, Fall 2019, with Jiaheng Lu.
Data Science Project, University of Helsinki, Fall 2019.

Data Science, INSA Lyon, Fall 2017.
Modern Database Systems, Aalto, Spring 2017, with Aristides Gionis.
Modern Database Systems, Aalto, Spring 2016, with Aristides Gionis.
The course covers (i) relational database systems and disk access analysis, (ii) querying and indexing for semi-structured data and text, (iii) Map-Reduce and Apache Spark.
Mining the Social Web, Aalto, Spring 2015, with Aristides Gionis.

Advisor for:

  • Jere Vaara’s BSc thesis (2016).
    Topic: ‘A Facebook bot for schedule coordination’.
  • Miika Rantakaulio’s BSc thesis (2016).
    Topic: ‘A Facebook bot for place recommendation’.
  • Clemens Westrup’s MSc thesis (2016), supported by Sanoma.
    Title: ‘An Exploration of Representation Learning and Sequential Modeling Approaches for Supervised Topic Classification in Job Advertisements’.
  • Julien Blegean’s MSc thesis (2015).
    Title: ‘Twitter the Rioter : Analyzing roles through a protest on social media. What was your part during the 2014 Ferguson riots?’
  • Geraud Le Falher’s MSc thesis (2014).
    Title: ‘Finding similar neighborhoods across cities by mining human urban activity’.