# From the quantum Hall effect to integral lattices and braided tensor categories

 Mathematical Conversations Topic: From the quantum Hall effect to integral lattices and braided tensor categories Speaker: Jürg Fröhlich Affiliation: ETH Zürich; Visiting Professor, School of Mathematics Date: Wednesday, February 19 Time/Room: 6:00pm - 7:00pm/Dilworth Room

Starting with a few remarks on hurricanes, I will sketch some basic facts about the physics of the Quantum Hall Effect. Assuming that the longitudinal conductance of a two-dimensional electron gas in a uniform magnetic field vanishes, I will explain why its Hall conductance must be a rational multiple of a constant of Nature, namely $e^{2}/h$, and how this is related to the theory of odd integral lattices and of certain braided tensor categories. About Mathematical Conversations: We meet in Harry's Bar at 6pm, where free drinks are provided. After 20 minutes, we move to the Dilworth room, where the speaker gives a 20-minute talk, followed by 15 minutes of discussion with the audience. After that we return to the bar for further discussions. Website: http://www.math.ias.edu/~nicks/conversations.html