Type: Seminar

Modified: Tue 27 Nov 2012 0024; Tue 27 Nov 2012 1637; Thu 29 Nov 2012 1225

Distribution: World

Expiry: 18 Dec 2012

Auth: zhangou@cpe-124-183-243-228.lns13.ken.bigpond.net.au (zhouz) in SMS-WASM

This is the first talk of the colloquium double-header. The second talk is announced at http://www.maths.usyd.edu.au/s/scnitm/zhangou-SYD-UNSWJointColloquium-J ************************************************************* Speaker: Prof. Susan Friedlander (USC) http://cams.usc.edu/~susanfri/ Time: Friday, Nov. 30, 2--3PM Room: Chemistry Lecture Theatre 2 Lunch plan: meet near Level 2 entrance to Carslaw Building around 1PM. The lunch would be at Law Annex Cafe with reservation at 1:05PM. Please keep in mind that our schedule would be a little tight with Algebra Seminar finishing at 1PM and the first colloquium talk starting at 2:05PM. Refreshments would be provided by the school in the common room on Level 7 around 4PM. ----------------------------------------------- Title: Active Scalar Equations and a Geodynamo Model Abstract: we discuss an advection-diffusion equation that has been proposed by Keith Moffatt as a model for the Geodynamo. Even though the drift velocity can be strongly singular, we prove that the critically diffusive PDE is globally well-posed. We examine the nonlinear instability of a particular steady state and use continued fractions to construct a lower bound on the growth rate of a solution. This lower bound grows as the inverse of the diffusivity coefficient. In the Earth’s fluid core this coefficient is expected to be very small. Thus the model does indeed produce very strong Geodynamo action. This work is joint with Vlad Vicol. ----------------------------------------------- Joint Colloquium web site: http://www.maths.usyd.edu.au/u/SemConf/JointColloquium/index.html