VIRTUAL Thursday, September 23th 2021 3:45 – 4:45 p.m. WEBEX Speaker: Prof. Bulbul Chakraborty Ancell Professor of Physics Head, Division of Science Brandeis University “Soft Capricious Matter: The collective behavior of particles with “noisy” interactions” Abstract: Diversity in the natural world emerges from the collective behavior of large numbers of interacting objects. Statistical physics provides the framework relating microscopic to macroscopic properties. A fundamental assumption underlying this approach is that we have complete knowledge of the interactions between the microscopic entities. But what if that, even though possible in principle becomes impossible in practice ? Can we still construct a framework for describing their collective behavior ? Dense suspensions and granular materials are two often quoted examples where we face this challenge. These are systems where because of the complicated surface properties of particles there is extreme sensitivity of the interactions to particle positions. In this talk, I will give two examples of theoretical progress that is charting a path forward to understanding rigidity and phase transitions in granular materials and dense suspensions. Bio: Bulbul Chakraborty is the Enid and Nate Ancell Professor of Physics at Brandeis University. She is recognized for her contributions to soft condensed matter theory studying systems far from equilibrium, such as granular materials, amorphous systems, and statistical physics. She is an elected American Physical Society and American Association for the Advancement of Science fellow. Chakraborty graduated with a BSc in Physics from the Indian Institute of Technology in 1974 and earned a PhD in 1979 from State University of New York, Stony Brook. The title of her PhD thesis is "Influence of thermal disorder on electronic properties of solids". She was a postdoctoral fellow at Argonne National Laboratory, NORDITA, Denmark, and a Research Associate at the Indian Institute of Science. She was a Scientific Officer (equivalent of Assistant Professor) at the Materials Science Laboratory, Indira Gandhi Center for Atomic Research (1984–1986), and an Associate Research Physicist and Lecturer, in Applied Physics, at Yale University (1987–1989). Chakraborty joined the faculty in the Physics Department at Brandeis University in 1989, where she has been Full Professor since 2000.[2] Chakraborty has made significant contributions to the understanding of the jamming transition in amorphous materials. Her group uses statistical frameworks to investigate the properties of shear-jammed[3][4] and densely packed particulate materials,[5][6][7] finding that elasticity and friction are correlated with athermal fluctuations in many disordered systems. Chakraborty is the Enid and Nate Ancell Professor of Physics at Brandeis University. She was elected fellow of the American Physical Society (APS) in 2008 "for important theoretical contributions to diverse areas of condensed matter physics, including frustrated magnets, diffusion of light particles in metals, the glass transition, and jamming in granular systems". In 2018, the Simons Foundation awarded Chakraborty a Simons Fellowship in Theoretical Physics.[12][13] Chakraborty was elected Fellow of the American Association for the Advancement of Science (AAAS) in 2020. https://www.brandeis.edu/physics/people/profiles/chakraborty-bulbul.html https://www.brandeis.edu/facultyguide/person.html?emplid=f9f1ab96c62ba815f7e621cadf96fd039a91b4a4