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Lossless approximations and the fluctuation-dissipation theorem

The fluctuation-dissipation theorem is a result of major importance in the field of statistical mechanics. It reveals a surprisingly simple relation between a dynamical system's response to small external perturbations and its inherent thermal noise. In this talk, we will present the theorem and show how it can be explained using a new result on constrained model approximation - so-called lossless approximation. The result says a linear system is dissipative if, and only if, it can be arbitrarily well approximated by a linear lossless system over finite time horizons. The talk is concluded by an example of how the fluctuation-dissipation theorem can be applied in a control loop to derive limitations on the accuracy and back action of sensors.

Type of Seminar:
IfA Seminar
Dr. Henrik Sandberg
KTH Royal Institute of Technology Stockholm, Sweden
Apr 19, 2011   11:00

ETZ E81, Gloriastrasse 35
Contact Person:

Roy Smith
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Biographical Sketch:
Henrik Sandberg received the M.Sc. degree in engineering physics and the Ph.D. degree in automatic control from Lund University, Lund,Sweden, in 1999 and 2004, respectively. From 2005 to 2007, he was a Postdoctoral Scholar at the California Institute of Technology, Pasadena.Since 2008, he has been an Assistant Professor in the Automatic Control Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden. He has also held visiting appointments at the Australian National University and the University of Melbourne, Melbourne, Australia. His research interests include modeling of networked systems, model reduction, linear systems,and fundamental limitations in control. Dr. Sandberg received the Best Student-Paper Award at the IEEE Conference on Decision and Control in 2004.