I was born in May 1943 in Kansas City Missouri when my father was serving in the Army in Alaska. After the war, he got a BA from Missouri Valley College in Marshall, Missouri and then a Master’s degree from the Georgetown School of Foreign Service. He was admitted to the Foreign Service in 1949, and was assigned to two-year stints in Germany, the Philippines, and Spain, followed by four years in Washington where I finished high school. After Sputnik and reading Fred Hoyle?s Frontiers of Astronomy, I developed a keen interest in astronomy, which, with luck, took me to Caltech, where I received a degree in physics. I did my Ph.D. work at Harvard under Paul Martin. I was awarded an NSF Fellowship to postdoc in France, where I entered the new field of liquid-crystal and more generally soft-matter physics in the lab of Nobelist Pierre Gils de Gennes. From there, I did a postdoc with Leo Kadanoff at Brown and then accepted an Assistant Professorship at Penn where I served until retirement in 2017. My wife, Amy, and I have been married for 52 years. We have two children, David and Ellen, and a granddaughter Molly.

Research Interests

I am a theoretical a theoretical condensed-matter physicist. In the past, I have carried out research on phenomenological theories of elasticity and dynamics of materials with broken continuous symmetries, liquid crystals, phase transitions and critical phenomena, percolation and related topics, quasicrystals, colloidal physics, microrheology, elasticity of biological gels, and granular materials and jamming. My current interest center on topological mechanics, which extends the enormously successful characterization of quantum materials in terms of the topological properties of their excitation spectra, to mechanical systems and, most recently, on "odd-viscosity" systems. As an example, in collaboration with Charlie Kane, I was able demonstrate that certain types of elastic lattices, which can be created using modern 3D printing, can one face that remains essentially undistorted in response to a point-like force whereas the opposite face undergoes large zero-energy distortions. Odd-viscosity is a phenomenon, first predicted theoretically by Lars Onsager, that occurs in fluid systems in which time-reversal symmetry (TRS) is broken: a new non-dissipative term that looks like viscous response appears in the hydrodynamical equations of the fluid. An active fluid composed of or containing spinning particles breaks TRS and has peculiar flow properties such as unidirectional surface waves.

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Primary Section

Section 33: Applied Physical Sciences

Secondary Section

Section 13: Physics