David Robert Nelson


David Robert Nelson is an American physicist, and Arthur K. Solomon Professor of Biophysics, at Harvard University. He is known for developing KTHNY theory.

Education

Nelson graduated from Cornell University Summa cum laude with a double major in physics and mathematics in 1972, and received an M.S. in theoretical physics in 1974, and a Ph.D. in theoretical physics in January, 1975. He was in the fourth and final class of Cornell's short-lived "Six-year Ph.D. program". His thesis was on applications of renormalization to critical phenomena, advised by Michael Fisher.
He then became a Junior Fellow in the Harvard Society of Fellows.
Nelson is currently the Arthur K. Solomon Professor of Biophysics and Professor of Physics and Applied Physics at Harvard University.

Research

Since 1978 he has been a professor at Harvard University. His research is in the fields of both hard and soft theoretical condensed matter physics, and of physical biology.
With his colleague, Bertrand Halperin, he is responsible for a theory of two-dimensional melting that predicted a fourth hexatic phase of matter, interposed between the usual solid and liquid phases. KTHNY theory is named after J. Michael Kosterlitz, David J. Thouless, Halperin and Nelson. A variety of predictions associated with this two-state freezing process have now been confirmed in experiments on two-dimensional colloidal assemblies, thin films and bulk smectic liquid crystals. Nelson's research also includes a theory of the structure and statistical mechanics of metallic glasses and investigations of tethered surfaces, which are two-dimensional generalizations of linear polymer chains. Flexural phonons lead a remarkable low temperature flat phase in these fishnet-like structures, with predictions of strongly scale-dependent elastic constants such as the two-dimensional Young's modulus and the bending rigidity of atomically or molecularly thin materials such as a free-standing sheets of graphene and molybdenum disulfide.
Nelson has also studied flux line entanglement in high temperature superconductors. At high magnetic fields, thermal fluctuations cause regular arrays of flux lines to melt into a tangled spaghetti state. The physics of this melted flux liquid resembles that of a directed polymer melt, and has important implications for both electrical transport and vortex pinning for many of the proposed applications of these new materials in strong magnetic fields.
David Nelson's recent investigations have focused on problems that bridge the gap between the physical and biological sciences, including dislocation dynamics in bacterial cell walls, range expansions and genetic demixing in microorganisms and localization in asymmetric sparse neural networks. Additional recent interests include the non-Hermitian transfer matrices that describe thermally excited vortices with columnar pins in Type II superconductors, the effect of perforations, cuts and other defects on atomically thin cantilevers at finite temperatures and topological defects on curved surfaces.

Awards

Notable works

  • Lidmar, Jack, Leonid Mirny, and David R. Nelson. "Virus shapes and buckling transitions in spherical shells." Physical Review E 68, no. 5 : 051910. DOI: https://doi.org/10.1103/PhysRevE.68.051910
  • Hallatschek, Oskar, Pascal Hersen, Sharad Ramanathan, and David R. Nelson. "Genetic drift at expanding frontiers promotes gene segregation." Proceedings of the National Academy of Sciences 104, no. 50 : 19926-19930. https://doi.org/10.1073/pnas.0710150104
  • Müller, Melanie JI, Beverly I. Neugeboren, David R. Nelson, and Andrew W. Murray. "Genetic drift opposes mutualism during spatial population expansion." Proceedings of the National Academy of Sciences 111, no. 3 : 1037-1042. https://doi.org/10.1073/pnas.1313285111