Seminar Calendar
for events the day of Tuesday, November 18, 2008.

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Questions regarding events or the calendar should be directed to Tori Corkery.
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Tuesday, November 18, 2008

Logic Seminar
1:00 pm   in 345 Altgeld Hall,  Tuesday, November 18, 2008
 Del Edit Copy
Submitted by ssolecki.
 Anand Pillay (University of Leeds)Generics and weight in the free groupAbstract: I discuss the notion of "weight" in a stable group. I will prove that the generic of the free group has infinite weight (strengthening nonsuperstability).

Harmonic Analysis and Mathematical Physics
1:00 pm   in Altgeld Hall,  Tuesday, November 18, 2008
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Submitted by bronski.
 Ralf Wittenberg (Simon Fraser University)Spatiotemporal Chaos with Strong Scale SeparationAbstract: Numerous physical, chemical and biological systems display the phenomenon of pattern formation: as a control parameter passes a critical value, a spatially uniform equilibrium becomes unstable to a stable nonuniform, finite-wavelength pattern. The scaling and stability of these patterned solutions beyond the instability threshold is by now well-understood via the Ginzburg-Landau partial differential equation, which describes modulations of the pattern (in one space dimension). I will discuss the profound effects of an additional continuous symmetry on pattern formation by describing recent results on the Nikolaevskiy equation, a paradigmatic (6th-order) PDE model for short- wave pattern formation with Galilean invariance. In this case, all periodic steady states are unstable beyond the instability threshold, and one observes a direct transition from spatial homogeneity to spatiotemporal chaos with strong scale separation. The asymptotically consistent modulation equation description associated to this PDE, proposed by Matthews and Cox, predicts scaling different from the usual Ginzburg-Landau scaling. I will present some of the novel dynamical and statistical behaviors of these PDE models. These include anomalous scaling of the large-scale mode inconsistent with the Matthews-Cox prediction (but captured by higher-order corrections to the amplitude equations), localized coexistence of ordered and chaotic states, coarsening to domain size-dependent fronts, and stabilization of Burgers-like fronts by spatiotemporal chaos.

Analysis Seminar
2:00 pm   in 347 Altgeld Hall,  Tuesday, November 18, 2008
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Submitted by aimo.
 Analysis tenure-track hiring meeting

Geometric Potpourri Seminar
2:00 pm   in 243 Altgeld Hall,  Tuesday, November 18, 2008
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Submitted by j-wetzel.
 No meeting this week.

Algebraic Geometry Seminar
3:00 pm   in 243 Altgeld Hall,  Tuesday, November 18, 2008
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Submitted by nevins.
 Mircea Mustata (University of Michigan)Sequences of log canonical thresholdsAbstract: The log canonical threshold of a function is an invariant that measures which powers of the function are locally integrable. This is an invariant that appears in many contexts, and that found many applications in birational geometry. I will discuss results and conjectures dealing with limit points of log canonical thresholds. This is joint work with Tommaso de Fernex.

Graph Theory and Combinatorics
3:00 pm   in 241 Altgeld Hall,  Tuesday, November 18, 2008
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Submitted by west.
 Alexandr Kostochka (Department of Mathematics, University of Illinois)Dense graphs have K3,t-minorsAbstract: Let K*3,t denote the graph obtained from K3,t by adding a triangle on the three vertices of degree t. Given n and t with n≥ t+3 and t≥ 9000, we prove that every n-vertex graph with more than (t+3)(n-2)/2+1 edges has K*3,t as a minor. The bound is sharp in the sense that for every t, there are infinitely many graphs G with (t+3)(|V(G)|-2)/2+1 edges that have no K3,t-minor. The result is a special case of Seymour's conjecture that every (s+t)-chromatic graph has a Ks,t-minor. This is joint work with Noah Prince.

Motivic Integration
3:00 pm   in 447 Altgeld Hall,  Tuesday, November 18, 2008
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Submitted by vlopes2.
 Vinicius C. L. (Department of Mathematics, University of Illinois)Grothendieck semiring of Presburger setsAbstract: We will read the first half of Raf Cluckers's paper "Presburger sets and p-minimal fields" (JSL 68, no. 1, 153 - 162 (2003), also available in arXiv). He proves that two infinite 0-definable Presburger sets are 0-definably equivalent if and only if they have the same cell dimension. We will study why this statement does not hold for sets definable with parameters, and will read his proofs trying to understand where they fail to generalize.

Analytic Aspects of Quantum Groups
3:00 pm   in 130 Lincoln Hall,  Tuesday, November 18, 2008
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Submitted by pfima.
 Steve Avsec (Department of Mathematics, University of Illinois)Fusion Rules and Haar Measure for SUq(2)Abstract: We will define the quantum group SUq(2), give the representation theory and the fusion rules and compute the Haar measure.