Hypatian Seminar

Speaker: Alethea Barbaro, UCLA

Title: Flocking, phase transitions, and associated PDEs

Abstract: Agent-based models are an increasingly important tool for mathematicians working in interdisciplinary mathematics, since they are highly flexible and easily explained to researchers in fields as diverse as physics, biology, criminology, psychology, computer science, and economics.Ê These types of models include both lattice and off-lattice models, and often exhibit interesting complex dynamics such as flocking behavior and phase transitions.Ê Recently, these models have also spawned an exciting and active area of research in mathematics by the derivation and analysis of associated kinetic and hydrodynamic PDEs.Ê In this talk, I will discuss my work on fish migration, gang territorial development, and flocking behavior and the analysis of associated systems.

Union, Health Care, and TA rights information session

Led by: Rob Ackermann and Filiberto Nolasco

Come learn about our graduate student health care, our rights as TAs, and about the union in general. As you may or may not know we are on a new healthcare plan called 'UCShip' this year. Bring questions!

Speaker: Ana Maria Carpio Rodriguez, Universidad Complutense Madrid

Title: Variational methods for image reconstruction and parameter identification, AC, UCM

Abstract:

A common strategy for finding multiple scatterers buried in a medium consists in illuminating the medium with some type of radiation. The emitted wave interacts with the medium and the objects, and the resulting wave field is measured at a number of receptors. Knowing the measured data, we would like to locate the objects and determine their material properties.

Variational methods aim to reconstruct objects by finding domains and parameters which minimize appropriate constrained cost functionals. In simple problems of acoustic or electromagnetic scattering, the incident radiation is time harmonic and the constraints of the cost functionals are transmission problems for Helmholtz equations.

We propose a descent strategy which provides detailed approxima tions of the geometry of the obstacles and their material parameters in few steps and with scarce data, without any a priori information. Initial guesses, and successive corrections of the domains are constructed using the topological derivative of the functional. The number, size and location of the objects are correctly approximated in the iterative procedure. Small scatterers and obstacles with holes are detected. Approximations for the material parameters of the different objects are found by a gradient technique that can detect spatial variations.

Similar ideas may be used in acoustic or electromagnetic scattering problems involving more complex constraints, in photothermal imaging with thermal waves or in electrical impedance tomography.

Organizational Meeting

Informal Roundtable

Topic: Last year of graduate school

Are you wondering what your last year at UCSB will be like? Join us for an informal roundtable with this year's graduating class. We'll discuss the ins and outs of finishing your dissertation while managing the job search and answer all of your nagging questions. Coffee and goodies provided by Hypation seminar. For more on the topic, check out Laura Zirbel's blog on preparing for your last year in math grad school: http://mathgradblog.williams.edu/year/

Panel Discussion

Topic: Applying for an Academic Job

We have compiled a terrific panel of experts with experience on both sides of the job search to answer your questions. Panelists include Alethea Barbaro (UCLA), Michael Gagliardo (California Lutheran University) and our own Marty Scharlemann. Job seekers should also check out the AMS webpage Advice for New PhDs - they have links to blogs, pdfs and websites covering everything from the job search to managing the first few years of your budding academic career.

Heather Russell, USC