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This lecture is an online discussion organised under our CCSS Societal Discussion Series: Fundamentals Issues of Complex Systems. In this lecture series, we focus on more philosophical and overarching issues of complex systems.

For the foreseeable future, lectures will remain predominantly online.

Speaker Overview

Didier Sornette is Professor on the Chair of Entrepreneurial Risks in the Department of Management, Technology and Economics at the Swiss Federal Institute of Technology Zurich (ETH Zurich). He is also a Professor at the Swiss Finance Institute and a Professor associated with both the department of Physics and the Department of Earth Sciences at ETH Zurich. Prof. Sornette is a founding member of the Risk Center at ETH Zurich and has published 500+ research papers and 7 books. In 2008, he founded the Financial Crisis Observatory to diagnose and predict financial bubbles. His research focuses on the predictability and control of crises and extreme events in complex systems with particular focus on financial bubbles, crashes, earthquake physics and geophysics, the dynamics of success on social networks and the complex system approach to medicine towards the diagnostic of systemic instabilities.

Abstract*

The "endo-exo" problem -- i.e., decomposing system activity into exogenous and endogenous parts -- lies at the heart of statistical identification in many fields of science. E.g., consider the problem of determining if an earthquake is a mainshock or aftershock, or if a surge in the popularity of a youtube video is because it is "going viral", or simply due to high activity across the platform.The "endo-exo" problem is also at the heart of a general description of the dynamics of out-of-equilibrium complex systems generalising the fluctuation-susceptibility theorem. 

I will present recent exciting results obtained in my group, which include:

1) The development of a powerful Expectation Maximization (EM) algorithm and objective statistical criteria (BIC) to select the flexibility of the deterministic background intensity of self-exciting Hawked point processes that have enjoyed great recent popularity and rapid development.

2) Seismicity and faulting within the Earth crust are characterized by many scaling laws that are usually interpreted as qualifying the existence of underlying physical mechanisms associated with some kind of criticality in the sense of phase transitions.

3) The Hawkes self-excited point process provides an efficient representation of the bursty intermittent dynamics of many physical, biological, geological, and economic systems.

4) The origin(s) of the ubiquity of Zipf’s law (an inverse power law form for the probability density function 11 (PDF) with exponent 1+1) is still a matter of fascination and investigation in many scientific fields from linguistic, social, economic, computer sciences to essentially all natural sciences.

Meeting Details

There will be 45-min lecture from the speaker, followed by a 45-min Question & Answer session.

To attend the lecture, please click this at 15:00 on Thursday 25th March 2021.

The event will be held via Zoom.

* This is a shortened version of the abstract. A longer version is available upon request from the organizer.