Date: Tuesday, September 16, 2025
Time: 3pm -4pm
Location: Seminar room EXP-610

Speaker: Christian Grussler (Technion – Israel Institute of Technology, visiting MIT)
Title:  Variation Diminishing in Systems Theory and Sparse Optimization

Abstract:   Variation diminishment, i.e., the reducing of zero-crossings or local extrema is an elementary property that we expect from common tools in filtering, statistics, geometric modeling or approximation theory. Total positivity, the old and well-established theory behind this property, however, has barely entered the respected communities and been mostly forgotten by now. In this talk, we will shed new light on the importance of this property in system analysis such as the study of self-oscillations, as well as in approximation theory such as model order reduction and sparse optimization. Basic mathematical concepts and our recent theoretical extension of those will be reviewed based on graphical interpretations. 

This has been joint work with Prof. Rodolphe Sepulchre from KU Leuven, Dr. Thiago Burghi from the University of Cambridge, Prof. Tobias Damm from RPTU Kaiserslautern as well as my students Chaim Roth, Maya M. Marmary and Kang Tong from the Technion. 

Biography:    Professor Grussler is currently an Assistant Professor at the Faculty of Mechanical Engineering, Technion – Israel Institute of Technology and a Jane and Larry Sherman Fellow. He conducts research that broadly intersects with the areas of Control Theory, Mathematical Optimization and Machine Learning. In particular, he is interested in the development of total positivity theory towards a unifying framework of these areas. 

Until January 2021, he was a Postdoctoral Scholar at the Department of Electrical Engineering and Computer Science, UC Berkeley, United States.  Prior to that, he was a Research Associate with the control group at the Department of Engineering, University of Cambridge, United Kingdom as well as a postdoc and PhD student at the Department of Automatic Control, Lund University, Sweden.  

In his undergraduate studies, I was part of a double degree program between the University of Kaiserslautern and Lund University. He received an MSc in Engineering Mathematics from Lund University and a Dipl.-Math. techn. in Industrial Mathematics from the University of Kaiserslautern.