Physics Seminar: Sloppy models, differential geometry, and why science works | James Sethna скачать в хорошем качестве

Physics Seminar: Sloppy models, differential geometry, and why science works | James Sethna

Online Physics seminar by Professor James Sethna (Cornell University), held on 9 October 2020. Abstract: Models of systems biology, climate change, ecology, complex instruments, and macroeconomics have parameters that are hard or impossible to measure directly. If we fit these unknown parameters, fiddling with them until they agree with past experiments, how much can we trust their predictions? We have found that predictions can be made despite huge uncertainties in the parameters – many parameter combinations are mostly unimportant to the collective behavior. We will use ideas and methods from differential geometry and approximation theory to explain sloppiness as a ‘hyperribbon’ structure of the manifold of possible model predictions. We show that physics theories are also sloppy – that sloppiness may be the underlying reason why the world is comprehensible. We will present new methods for visualizing this model manifold for probabilistic systems – such as the space of possible universes as measured by the cosmic microwave background radiation. Bio: Sethna is a professor of Physics at Cornell University, with a long and productive research career in condensed matter physics, statistical mechanics, biological physics, and materials science. He was one of the early leaders in the study of the onset of chaos and the systematic study of crackling noise; he received the Presidential Young Investigator award and a Sloan Foundation fellowship to support his early research. He has contributed extensively to many fields of science, including phase transitions and dynamics of disordered materials, plasticity, fracture, and dynamical systems and chaos. He has supervised 33 graduate students who have gone on to leadership positions in academia (full professors at Berkeley, UCSB, Ohio State, Urbana, and Cornell) and industry (CEO and founder of Gene Network Sciences, vice president at URS Corp, and CTO at HealthEdge), and has worked with over twenty post-doctoral fellows who have become professors at UCLA and University of Michigan, dean of the Franklin College of Arts and Sciences, and Managing Director of Microsoft Research New England. He is the author of a textbook, “Statistical Mechanics: Entropy, Order Parameters, and Complexity”, whose second edition will be coming out in January 2021.