2017.12.15 Localization in Biological Networks

2019-07-07 00:51:52 1



题    目:Localization in Biological Networks.

报告人David R. Nelson

Member of the National Academy of Sciences

Member of the American Academy of Arts and Sciences

Fellow of the American Physical Society

Professor of Physics and Applied Physics

Arthur K. Solomon Professor of Biophysics Lyman Laboratory, Harvard University

时    间:12月15日(周五)15:00-16:00

地    点:北京大学老化学楼东配楼101报告厅

主持人:汤超 教授

摘 要:

In the 70 years since Phillip Anderson proposed his ideas about localized states in disordered systems, it has become clear that virtually all electronic states are localized in one-dimension. We show that the situation is quite different when the hopping matrix becomes non-Hermitian.  Non-Hermitian matrices, with complex eigenvalue spectra, arise naturally in simple models of complex ecosystems, with many interacting predator and prey species.  Recent work has revealed particularly striking departure from the conventional wisdom in the one-dimensional non-Hermitian random matrices that describe sparse neural networks.  Approximately equal numbers of random excitatory and inhibitory connections lead to an intricate fractal eigenvalue spectrum that controls the spontaneous activity and induced response.   When rings of neurons become directed, with a systematic bias for the transfer of excitations in the clockwise direction, a hole centered on the origin opens up in the density of states in the complex plane.   All states are extended on the rim of this hole, while the states outside the hole are localized.