Events
Past Event
NICO DECEMBER SEMINAR: Scott Feld, Purdue University "Finding Highly Connected Nodes in Networks: The Power of Common Friends"
Northwestern Institute on Complex Systems (NICO)
11:00 AM
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Lower Level, Chambers Hall
Details
Speaker:
Scott Feld, Professor of Sociology, Purdue University
Title:
Finding Highly Connected Nodes in Networks: The Power of Common Friends
Abstract:
This paper extends the Friendship Paradox – where friends have more friends than random people do, on average – to the more general phenomenon that mutual friends have more friends than friends do, on average. We show that we can find people who who are friends of multiple people in practical sized random samples in one regional Facebook network of 63,392 people with an average of 24 friends each, where people with two friends in a random sample have an average of 212 friends overall, with three friends have an average of 391 friends, etc. We further illustrate this general network phenomenon by taking random samples of citations from 79,034 journal articles. We find that a source cited by two articles in a random sample has an average of 461 citations, placing it in the top 0.01% in numbers of citations among all sources cited by these articles. We provide a general expression for the expected overall number of friends of a person found to have k friends in a random sample from a population with a given distribution of numbers of friends. We show that the effectiveness of using common friends among random samples for finding highly connected nodes is most pronounced when there are nodes with a great disproportion of the ties, as seems to be both typical and important for many types of social and other networks, such as where there are superspreaders of diseases, mega-influencers on the Internet, and highly connected central nodes in centralized neural networks. We discuss further implications, applications, and directions for further research.
Speaker Bio:
Scott Feld served as Assistant to Full Professor of Sociology at the State University of New York at Stony Brook from 1975-1991. He then served as Professor of Sociology at Louisiana State University from 1991 until 2004, and joined the faculty at Purdue University in 2004. He has published over sixty articles, including twelve published in the most prestigious journals in the fields of Sociology and Political Science. His ongoing research interests involve 1) causes and consequences of patterns in social networks, 2) processes of individual and collective decision making, and 3) applications of sociology, most recently including innovations in marriage and divorce laws (covenant marriage). He regularly teaches undergraduate and graduate courses on social networks, research methods, and statistics.
Location:
In person: Chambers Hall, 600 Foster Street, Lower Level
Remote option: https://northwestern.zoom.us/j/91453237911
Passcode: NICO2024
Time
Tuesday, December 3, 2024 at 11:00 AM - 12:00 PM
Location
Lower Level, Chambers Hall Map
Contact
Calendar
Northwestern Institute on Complex Systems (NICO)
No Classes - Martin Luther King Jr. Day (University Offices Closed)
University Academic Calendar
All Day
Details
No Classes - Martin Luther King Jr. Day (University Offices Closed)
Time
Monday, January 20, 2025
Contact
Calendar
University Academic Calendar
WED@NICO SEMINAR: István Kovács, Northwestern University "The Brain as a Critical Spatial Network"
Northwestern Institute on Complex Systems (NICO)
12:00 PM
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Lower Level, Chambers Hall
Details
Speaker:
István Kovács, Assistant Professor, Department of Physics and Astronomy, Northwestern University
Title:
The Brain as a Critical Spatial Network
Abstract:
Recent cellular-level volumetric brain reconstructions have revealed petabytes of information about the astronomical level of anatomic complexity. Determining which structural aspects of the brain to focus on, especially when comparing with computational models and other organisms, remains a major challenge. Recently, we utilized tools from statistical physics to show that cellular brain anatomy satisfies universal scaling laws, establishing the notion of "structural criticality" in the cellular structure of the brain. For example, we obtain estimates for critical exponents in the human, mouse and fruit fly brains and show that they are consistent between organisms, to the extent that data limitations allow. Such universal quantities are robust to many of the microscopic details of the cellular structures of individual brains, providing a key step towards generative computational models, and also clarifying in which sense one animal may be a suitable anatomic model for another. Therefore, our framework provides clear guidance in selecting informative structural properties of cellular brain anatomy. Similarly, in terms of the complex interplay between the spatial and topological aspects of the neural connectome, we showed that brain networks share simple organizing principles across the studied organisms. We used these observations to design scalable generative network models, and demonstrated predictive power beyond the input data, as they capture several additional biological and network characteristics, like synaptic weights and graphlet statistics. Currently, with our experimental collaborators, we are working on incorporating transcriptomics data into our models to also understand the underlying genetic wiring rules of brain organization. As in the brain the hardware is the software, even with all the remaining open questions, our results are expected to have broad implications on brain function and dynamics.
References:
[1] H. S. Ansell and I. A. Kovács (2024) Unveiling universal aspects of the cellular anatomy of the brain, Communications Physics, 7, 184
[2] A. Salova and I. A. Kovács (2024) Combined topological and spatial constraints are required to capture the structure of neural connectomes, Network Neuroscience, 1-41
Speaker Bio:
István Kovács is Assistant Professor in the Department of Physics and Astronomy at Northwestern University, a core member of NICO and NITMB, with a courtesy appointment in the Department of Engineering Science and Applied Mathematics. He is a recipient of the 2025 NSF CAREER Award, the Karl Rosengren Faculty Mentoring Award in 2021 and 2023, and was selected for the 2021-2022 Faculty Honor Roll at Northwestern University, for powerful and exceptional impact on student experience. Previously he was a postdoctoral fellow in the Network Science Institute at Northeastern University, a visiting researcher in the Center for Cancer Systems Biology at the Dana-Farber Cancer Institute and at University of Toronto, as well as at the Department of Network and Data Science of the Central European University. He received a PhD in Physics from the Eötvös Loránd University in Hungary, working at the Wigner Research Centre for Physics. His group develops novel methodologies to predict the emerging structural and functional patterns in problems ranging from systems biology to quantum physics, in close collaboration with experimental groups.
Location:
In person: Chambers Hall, 600 Foster Street, Lower Level
Remote option: ZOOM TBA
Passcode: TBA
About the Speaker Series:
Wednesdays@NICO is a vibrant weekly seminar series focusing broadly on the topics of complex systems, data science and network science. It brings together attendees ranging from graduate students to senior faculty who span all of the schools across Northwestern, from applied math to sociology to biology and every discipline in-between. Please visit: https://bit.ly/WedatNICO for information on future speakers.
Time
Wednesday, January 22, 2025 at 12:00 PM - 1:00 PM
Location
Lower Level, Chambers Hall Map
Contact
Calendar
Northwestern Institute on Complex Systems (NICO)
Winter Classes End
University Academic Calendar
All Day
Details
Winter Classes End
Time
Saturday, March 15, 2025
Contact
Calendar
University Academic Calendar
Spring Classes Begin - Northwestern Monday: Classes scheduled to meet on Mondays meet on this day.
University Academic Calendar
All Day
Details
Spring Classes Begin - Northwestern Monday: Classes scheduled to meet on Mondays meet on this day.
Time
Tuesday, April 1, 2025
Contact
Calendar
University Academic Calendar