Department of

# Mathematics

Seminar Calendar
for events the day of Monday, February 20, 2006.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
     January 2006          February 2006            March 2006
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5  6  7             1  2  3  4             1  2  3  4
8  9 10 11 12 13 14    5  6  7  8  9 10 11    5  6  7  8  9 10 11
15 16 17 18 19 20 21   12 13 14 15 16 17 18   12 13 14 15 16 17 18
22 23 24 25 26 27 28   19 20 21 22 23 24 25   19 20 21 22 23 24 25
29 30 31               26 27 28               26 27 28 29 30 31



Monday, February 20, 2006

12:00 pm in 2405 Siebel Center,Monday, February 20, 2006

#### Coarsening in Adaptive Algebraic Multigrid

###### S. MacLachlan (University of Minnesota, CS)

Abstract: Note: alternate time and location. This seminar is joint with the CSE Seminar.

Numerical simulation of physical processes is often constrained by our ability to solve the complex linear systems at the core of the computation. Multiscale methods, such as multigrid, provide optimal or near-optimal order solution techniques for many of these systems, relying on the use of complementary problems to reduce errors that simple iterative methods, such as Jacobi or Gauss-Seidel, are slow to resolve. Thus, classical geometric and algebraic multigrid methods rely on (implicit) assumptions about the character of these matrices in order to develop appropriately complementary coarse-grid correction processes for a given relaxation scheme. The aim of the adaptive multigrid framework is to reduce the restrictions imposed by such assumptions, thus allowing for efficient black-box multigrid solution of a wider class of problems. There are, however, many challenges in altogether removing the reliance on assumptions about the errors left after relaxation, particularly in the choice of coarse-grid points. In this talk, we introduce the adaptive AMG framework and discuss its application to problems in heterogeneous media. Recent research on purely algebraic criteria for coarse grid selection will also be discussed.

2:00 pm in 143 Altgeld Hall,Monday, February 20, 2006

#### Group von Neumann algebras and crossed products

###### Caleb Eckhard (UIUC)

3:00 pm in 343 Altgeld Hall,Monday, February 20, 2006

#### The Quantum Open String

###### Sean Nowling (UIUC Physics)

Abstract: The spectrum of the quantum open string will be discussed, including the introduction of D-branes.

4:00 pm in 347 Altgeld Hall,Monday, February 20, 2006