SIAM Student Chapter
Archive

Spring 2008

March

03/12
Bob Breault (Breault Co.), Hyrum Cotrell (Edward Jones), Diana J. Kennedy (Raytheon), Alaina Levine (UA PSM), William Velez (US Navy, UA Math), Olga Yiparaki (IBM)

Finding and Getting Post-Graduation Industry Work: A Panel Discussion

Interested in exploring career options outside of academia and national laboratories? Come participate in a panel discussion with mathematicians who are successfully working in various industries and Ms. Levine, who directs the Professional Science Masters program and is a highly successful entrepreneur and motivational speaker. And of course there will be food.

April

04/23
Sumit Mazumdar
Department of Physics
The University of Arizona

Repulsive Coulomb Interactions and Unconventional Superconductivity

The history of superconductivity has been referred to as the history of quantum mechanics. Following the first observation of the phenomenon in 1911, it took nearly five decades to arrive at the now-famous Bardeen-Cooper-Schrieffer (BCS) theory of "low Tc" superconductivity. Even more person-years have, however, gone into research on the mechanism of "high Tc" superconductivity, which was discovered in 1986, and about which there is no consensus to date.

In the first part of this talk I will briefly discuss the surprises and challenges that make the high Tc problem such a formidable one. The difficulty arises not merely in the high critical temperatures of the superconductors but also in the dominant repulsive interaction among the charge carriers, which make the simple BCS theory inapplicable to these systems. Following this, I will point out that there is now general agreement that similar repulsive interactions characterize many other unconventional superconductors, and there exists therefore an entire class of systems that lie outside the scope of the BCS theory. I will then focus on one such family of materials, organic charge-transfer solids, and discuss our recent advances towards understanding the mechanism of superconductivity in these. It is conceivable that this particular mechanism is applicable to correlated electron superconductors in general.

04/30
Simge Kucukyavuz
Department of Systems and Industrial Engineering
The University of Arizona

Mixed-Integer Optimization for Production and Distribution Planning Problems

We study the polyhedral structure of the uncpacitated single-item lot-sizing problem with backlogging. We give an explicit linear description of the convex hull of solutions to this problem in its natural space of production, setup, inventory, and backlogging variables. We describe a separation linear program for our proposed inequalities as well as the first exact combinatorial separation algorithm for a well-known special case. To illustrate the effectiveness of our inequalities, we report a summary of computational experiments with a branch-and-cut algorithm on a class of NP-hard multi-item lot-sizing problems. Finally, we show that our results can be generalized to give strong inequalities for uncapacitated fixed-charge network flow polyhedra that arise in distribution planning problems.

Lunch/refreshments provided.