Complexity & Society Lab

Welcome to the Complexity & Society Lab (“&-Lab”) at Northeastern University’s Network Science Institute. We develop methods for modeling multi-scale and dynamic networks—spanning graph comparison, inference, and machine learning—and apply them to domains such as urban systems, criminal justice, public health, neuroscience, and sports analytics. By combining information theory, Bayesian inference, and complex-systems science with large-scale data, we try to uncover mechanisms that drive collective behavior and emergence, ultimately informing interventions that build more resilient and equitable social systems.

Lab Members

Brennan Klein, Director

Brennan Klein is core faculty the Network Science Institute at Northeastern University and an Assistant Teaching Professor in the Department of Physics. He studies complex systems across nature and society using tools from network science and statistics. His research sits in two broad areas: First, he develops methods and theory for constructing, reconstructing, and comparing complex networks based on concepts from information theory and random graphs. Second, he uses an array of interdisciplinary approaches to document—and combat—emergent or systemic disparities across society, especially as they relate to public health and public safety. In addition to his role at Northeastern University, Brennan is the Data for Justice Fellow at the Institute on Policing, Incarceration, and Public Safety in the Hutchins Center for African and African American Studies at Harvard University. Brennan received a PhD in Network Science from Northeastern University in 2020 and a B.A. in Cognitive Science from Swarthmore College in 2014.

Maddalena Torricelli, Postdoctoral Researcher (Sports Analytics)

Maddalena Torricelli is a postdoctoral researcher specializing in sports analytics. She holds a PhD in Data Science and Computation from the University of Bologna, with a focus in complex systems physics and computational social science. Her research interests have spanned from studying temporal networks, dynamic process modeling, and polarization and misinformation, particularly in the context of climate change and natural disasters. Now, she focuses on the application of network science and data analytics to sports systems, leveraging complex systems theories and methods to address sports-related challenges. Website: https://maddalenatorricelli.me/.

Isaac Dalke, Postdoctoral Researcher (Data Justice)

Isaac Dalke is an incoming postdoctoral researcher, starting August 2025. He completed his PhD in Sociology at UC Berkeley, specializing in the intersection of law, politics, and urban life. His research examines the evolution of the penal state and the role of nonprofits in addressing social issues in American cities. Isaac’s dissertation focused on community-based violence prevention initiatives across California, investigating how these efforts are envisioned, implemented, and evaluated through nonprofit contracting. Methodologically, he integrates interpretive analysis with Natural Language Processing techniques, notably applied to studying decision-making in penal institutions, such as the California parole board. In the &-Lab, Isaac will be leading our studies in the U.S. criminal municipal court system. Website: https://sociology.berkeley.edu/graduate-student/isaac-dalke.

Moritz Laber, PhD Student (Network Science)

Moritz Laber is a 4th year PhD student in Network Science at Northeastern University. He is broadly interested in the mutual influence of network structure and dynamics. Currently, he is using methods from information theory to identify structure at different scales in complex systems. Before joining NetSI, Moritz studied how supply shocks propagate on the global food production network. He received a BS and MS in Physics from Karlsruhe Institute of Technology and a MS in Computational Science from University of Vienna. Website: https://moritz-laber.github.io/.

Erik Weis, PhD Student (Network Science)

Erik Weis is a 2nd year PhD student in Network Science at Northeastern University. His interests involve using complex systems modeling to improve the design of policy interventions. His past research has explored the impact of uncertainty on the design of optimal network interventions. Before joining NetSI, Erik received a MS in Complex Systems and Data Science from the University of Vermont and a BA in Physics from Dartmouth College. Website: https://erikweis.com/.

Lochan Chaudhari, PhD Student (Network Science)

Lochan Chaudhari is a 2nd year PhD student in Network Science at Northeastern University. Her research interests lie in applying tools from complex systems and statistical physics to explore the complexities of biological systems, with a particular emphasis on neuronal systems. Previously, Lochan studied the dynamics of coupled neurons, their networks, and their interactions with astrocytes. Lochan received a BS-MS in Physics from the Indian Institute of Science Education and Research in Tirupati. Website: https://www.networkscienceinstitute.org/people/lochan-chaudhari.

Chethan Kavaraganahalli Prasanna, PhD student (Network Science)

Chethan Kavaraganahalli Prasanna is a 1st-year PhD student in Network Science at Northeastern University. His research interests center around foundational network theory, collective behavior, and inference in complex systems. Chethan completed his MS in Computer Science at the University of Colorado Boulder, focusing on theoretical and computational approaches to network dynamics and collective phenomena. Website: https://www.linkedin.com/in/chethan-kp-113387146/.

Lab Alumni

Eline Bouwmeesters

Visiting MS Student (AccelNet-MultiNet Fellow, ‘24)

Janne de Rooij

Visiting MS Student (AccelNet-MultiNet Fellow, ‘24)

Lena Mangold

Visiting PhD Student (2024)

Harrison Hartle

PhD Student (2023)

Conor Heins

Research Assistant

Daphne Demekas

Research Assistant

Research Areas

Website in progress.

News & Lab Updates

  • December 9, 2025 — Brennan Klein leading tutorial session at Complex Networks 2025.

  • October 23 - October 24, 2025 — Brennan Klein and Isaac Dalke presenting at the Convening on Criminal Municipal Court Reform at Rutgers University.

  • September 22 - September 24, 2025 — Brennan Klein attending the Santa Fe Institute working group on AI in the Criminal Justice System.

  • July 21 - July 24, 2025 — IC2S2 2025 in Norrköping, Sweden. (italics=presenter)

    • Regionalization via nonparametric community detection in spatially embedded networks. Weis, E., Laber, M., Kirkley, A., & Klein, B. (talk)

    • The temporal dimension of experienced segregation in cities. Rosen, J., Weis, E., Gibbs, H., Yabe, T., Klein, B., O’Brien, D., Moro, E. (talk)

  • June 23 - June 27, 2025 — Maddalena Torricelli and Brennan Klein attend Complexity72h as tutors, alongside Prof. Javier Buldú, on the project, Harder, shorter, sharper, forward: A comparison of women's and men's elite football gameplay (2020-2025).

  • June 8 - July 4, 2025 — Moritz Laber participating in the Santa Fe Institute Complex Systems Summer School.

  • June 1 - June 5, 2025 — NetSci 2025 in Maastricht, The Netherlands. (italics=presenter)

    • Generalization and efficiency of graph neural ODEs for network dynamical systems. Laber, M. & Klein, B. (talk)

    • Regionalization via nonparametric community detection in spatially embedded networks. Weis, E., Laber, M., Kirkley, A., & Klein, B. (talk)

    • Modeling institutional prestige through inter-university collaboration networks. Chaudhari, L., Dorantes-Gilardi, R., & Klein, B. (poster)

    • Higher-order network effects on information access equality and efficiency. Laber, M., Dies, S., Ehlert, J., Klein, B., & Eliassi-Rad, T. (talk)

    • A comparison of network sampling techniques that preserve local structure. Bouwmeesters, E., van der Hoorn, P., & Klein, B. (talk)

    • Growing unlabeled networks. Hartle, H., Klein, B., Krapivsky, P., & Krioukov, D. (poster)

    • A review of coarse-graining methods: Insights from physics, network science, and computer science. Aleta, A., Boucherie, L., Chaudhari, L., Arribas, A., Fernández da Silva, M., Ferri, I., Fosch, A., Freitas, V., Hartle, H., Klein, B., Urbinati, A., Weis, E., Venturini, S. (poster)

    • Information loss in models of communication across populations. Kumar, S., Laber, M., Majumder, M., Foucault Welles, B. (poster)

  • April 24, 2025 — Erik Weis receives prestigious NSF NRT PEAR Traineeship.

  • April 1, 2025 — Maddalena Torricelli joins the lab as a postdoctoral researcher, focusing on NetSI Sport—a new initiative in sports analytics at the Network Science Institute.

  • March 3 - March 5, 2025 — NSF AccelNet-MultiNet Collabathon at Northeastern University.

  • January 1, 2025 — Brennan Klein promoted to core faculty at the Network Science Institute, Assistant Teaching Professor in the Department of Physics, and director of the MS Program in Complex Network Analysis.

Lab Culture & Scientific Philosophy

Website in progress.

Misc.

  • November 19, 2024 - Slides from invited talk at the Mathematical Institute at the University of Oxford: Network Comparison and Graph Distances: A Primer and Open Questions.

  • October 22, 2024 - Slides from invited talk at the Santa Fe Institute: Simple Injustice, Complex System: Data and inequalities of policing, sentencing, and incarceration in the U.S.

  • March 13, 2024 - Slides from &-Lab Introduction presentation.