Jukka-Pekka Onnela is a Fulbright Visiting Scholar at the Kennedy School, Harvard University. He holds a PhD from Helsinki University of Technology, Finland, in Complex Systems. These are systems consisting of a large number of interacting elements that result in the system becoming organised without any external organising principle being applied. Consequently, decomposing the system and studying its subparts in isolation does not contribute to understanding it. Instead, one needs to adopt a system-level perspective using the framework of complex networks.
Jukka-Pekka's earlier research explored the structure of financial markets. More recently he has worked on network models and methods and analysed the properties of social interaction networks constructed from the cell phone calls of millions of individuals. His current research focuses on communication networks and digital media, especially Facebook, and the dynamics of group formation, group performance, and social influence in these systems.
Jukka-Pekka also holds a Research Fellowship in Complex Systems at Oxford University.
A19 J.-P. Onnela, N. F. Johnson, S. Gourley, G. Reinert, and M. Spagat, Sampling bias due to structural heterogeneity and limited internal diffusion , submitted to Europhysics Letters 85, 28001 (2009).
A18 J. M. Kumpula, J.-P. Onnela, J. Saramäki, J. Kertész, and K. Kaski, Model of community emergence in weighted social networks , Computer Physics Communications, in print (2008).
A17 J.-P. Onnela, J. Töyli, and K. Kaski, Decimalization and asset returns , Physica A, in print (2008).
A16 N. F. Johnson, M. Spagat, S. Gourley, J.-P. Onnela, and G. Reinert, Bias in epidemiological studies of conflict mortality , Journal of Peace Research, 45, 5, 653-663 (2008).
A15 D. M. D. Smith, C. F. Lee, J.-P. Onnela and N. F. Johnson, Link-space formalism for network analysis , Phys. Rev. E 77, 036112 (2008).
A14 J. M. Kumpula, J.-P. Onnela, J. Saramäki, K. Kaski, and J. Kertész, Emergence of communities in weighted networks , Phys. Rev. Lett. 99, 228701 (2007).
A13 J.-P. Onnela, J. Saramäki, J. Hyvönen, G. Szabó, D. Lazer, K. Kaski, J. Kertész, and A.-L. Barabási, Structure and tie strengths in mobile communication networks , Proc. Natl. Acad. Sci. USA 104, 7332-7336 (2007).
A12 J.-P. Onnela, J. Saramäki, J. Hyvönen, G. Szabó, M. Argollo de Menezes, Kimmo Kaski, A.-L. Barabási, and J. Kertész, Analysis of a large-scale weighted network of one-to-one human communication , New Journal of Physics 9, 179 (2007).
A11 D. M. D. Smith, J.-P. Onnela, and N. F. Johnson, Accelerating networks , New Journal of Physics, 9, 181 (2007).
A10 T. Heimo, J. Saramäki, J.-P. Onnela, and K. Kaski, Spectral and network methods in the analysis of correlation matrices of stock returns , Physica A 383, 147-151 (2007).
A9 J. Saramäki, M. Kivelä, J.-P. Onnela, K. Kaski, and J. Kertész, Generalizations of the clustering coefficient to weighted complex networks , Phys. Rev. E, 75 027105 (2007).
A8 G. Tibély, J.-P. Onnela, J. Saramäki, K. Kaski, and J. Kertész, Spectrum, intensity and coherence in weighted networks of a financial market , Physica A 370, 145-150 (2006).
A7 R. Toivonen, J.-P. Onnela, J. Saramäki, J. Hyvönen, and K. Kaski, Model for social networks , Physica A 371, 851 (2006).
A6 J.-P. Onnela, J. Saramäki, J. Kertész, and K. Kaski, Intensity and coherence of motifs in weighted complex networks , Physical Review E 71, 065103 (2005).
A5 J.-P. Onnela, K. Kaski, and J. Kertész, Clustering and information in correlation based financial networks , European Physical Journal B 38, 353-362 (2004).
A4 J.-P. Onnela, A. Chakraborti, K. Kaski, J. Kertész, and A. Kanto, Asset trees and asset graphs in financial markets , Physica Scripta 106, 48-54 (2003).
A3 J.-P. Onnela, A. Chakraborti, K. Kaski, J. Kertész, and A. Kanto, Dynamics of market correlations: Taxonomy and portfolio analysis , Physical Review E 68, 056110 (2003).
A2 J.-P. Onnela, A. Chakraborti, K. Kaski, and J. Kertész, Dynamic asset trees and Black Monday , Physica A 324/1-2, 247-252 (2003).
A1 J.-P. Onnela, A. Chakraborti, K. Kaski, and J. Kertész, Dynamic asset trees and portfolio analysis , European Physical Journal B 30, 285-288 (2002).
Articles Under Review
R3 D. M. D. Smith, J.-P. Onnela, and N. S. Jones, Master-equation analysis of accelerating networks , submitted to Phys. Rev. E (2008). Preprint: arXiv:0810.4119.
R2 R. Toivonen, L. Kovanen, M. Kivelä, J.-P. Onnela, J. Saramäki, and K. Kaski, A comparative study of stochastic algorithmic models for social networks , submitted to Social Networks (2008). Preprint: arXiv:0805.0512.
R1 D. M. D. Smith, J.-P. Onnela, C. F. Lee, M. Fricker, and N. F. Johnson, Network automata and the functional dynamic network framework , submitted to Phys. Rev. E (2007). Preprint: arXiv:physics/0701307v2.
C4 R. Toivonen, J. M. Kumpula, J. Saramäki, J.-P. Onnela, J. Kertész, and K. Kaski, The role of edge weights in social networks: modelling structure and dynamics , in J. Kertesz et al (eds.), Proceedings of SPIE: Noise and Stochastics in Complex Systems and Finance, Proc. of SPIE 6601, 660110 (2007).
C3 J.-P. Onnela, J. Saramäki, J. Kertész, and K. Kaski, Financial market - a network perspective in: H. Takayasu (Ed.), Practical Fruits of Econophysics, Nikkei Econophysics III Proceedings, Springer, Tokyo, 302 (2006).
C2 J. Saramäki, J.-P. Onnela, J. Kertész, and K. Kaski, Characterizing motifs in weighted complex networks in: J.F.F. Mendes, et al. (Eds.), Science of Complex Networks - AIP Conference Proceedings 776, 108 (2005).
C1 J.-P. Onnela, K. Kaski, and J. Kertész, Financial market - a network of capital flows , InterJournal Complex Systems, 936 (5/2004).
W3 J.-P. Onnela, S. Reid, N. Jones, M. A. Porter, and P. J. Mucha, Dynamic community spectroscopy.
W2 M. Beguerisse-Díaz, M. A. Porter, and J.-P. Onnela, Analysis and model of a bipartite network of movie ratings.
W1 M. A. Porter, J.-P. Onnela, and P. J. Mucha, Statistical mechanics of network communities.
T2 J.-P. Onnela, Complex networks in the study of financial and social systems ,
Laboratory of Computational Engineering, Helsinki University of Technology, Finland (2006).
T1 J.-P. Onnela, Taxonomy of Financial Assets ,
Laboratory of Computational Engineering, Helsinki University of Technology, Finland (2002).
P1 J. Saramäki, J.-P. Onnela, K. Kaski, Kompleksisten verkostojen fysiikkaa (Physics of complex networks) , Arkhimedes 1 (2007).
M8 Selbstmord durch Ansteckung, Der Spiegel, 28 April 2008.
M7 Heikot linkit - verkon elinehto, Helsingin Sanomat, 29 May 2007.
M6 Study maps network of 7 million cell phone users, PhysOrg.com, 12 May 2007.
M5 Cellphone study shows the ties that bind nations, New Scientist, 24 April 2007.
M4 Flüchtige Bekanntschaften halten die Info-Gesellschaft zusammen, Spiegel Online, 25 April 2007.
M3 Mobile-phone network reveals the ties that bind, PhysicsWeb, 31 October 2006.
M2 Tracking people's electronic footprints, Science 314, 914-916 (2006).
M1 Death toll in Iraq: survey team takes on its critics, Nature 446, 6-7 (2007).
Harvard International Development Conference, Harvard University, April 2009.
Using mobile phones to study social networks, Oxford University, January 2009.
Complex systems in a nutshell - Tracing our digital footprints, Oxford University, July 2008.
Structure and modelling of large-scale social networks, Network Science 2008, Norwich, UK, June 2008.
Emergence of communities in weighted social networks, CCP2007, Brussels, September 2007.
Main street bias in epidemiological surveys of conflict mortality, Helsinki, July 2007.
Tieteen viikko, Yleisradio (Weekly Science News in Finnish)
Conflict mortality surveys