Seminar Calendar
for events the day of Tuesday, April 19, 2011.

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Questions regarding events or the calendar should be directed to Tori Corkery.
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Tuesday, April 19, 2011

Topology Seminar
11:00 am   in 241 Altgeld Hall,  Tuesday, April 19, 2011
 Del Edit Copy
Submitted by mando.
 Charles Rezk (UIUC Math)On the telescope conjecture

Ergodic Theory
12:00 pm   in 241 Altgeld Hall,  Tuesday, April 19, 2011
 Del Edit Copy
Submitted by jathreya.
 Aaron Hill (UIUC)Topological Similarity in the group of invertible measure-preserving transformationsAbstract: Abstract: Invertible measure-preserving transformations T and S are topologically similar if for every increasing sequence of natural numbers {i_n}, T^{i_n} converges to the identity iff S^{i_n} converges to the identity. There are strong connections between the collection of sequences that send a transformation T to the identity and mixing properties of T and the centralizer of T. We'll explore some of these connections.

Number Theory
1:00 pm   in 241 Altgeld Hall,  Tuesday, April 19, 2011
 Del Edit Copy
Submitted by berndt.
 Kenneth Williams (Carleton University)The number of solutions of n=a_1x_1^2+a_2x_2^2+a_3x_3^2+a_4x_4^2 for a class of positive integers a_1, a_2, a_3, a_4Abstract: Ideas going back to Liouville, Jacobi and Ramanujan are used to give an elementary approach to the problem of determining the number of solutions (x_1,x_2,x_3,x_4) in Z^4 of n=a_1x_1^2+a_2x_2^2+a_3x_3^2+a_4x_4^2 for all n in N when a_1, a_2, a_3, a_4 are in N are such that p \mid a_1 a_2 a_3 a_4 \Rightarrow p=2 or 3.

Graph Theory and Combinatorics
3:00 pm   in 241 Altgeld Hall,  Tuesday, April 19, 2011
 Del Edit Copy
Submitted by west.
 Jaehoon Kim (UIUC Math)Maximum hypergraphs without regular subgraphsAbstract: We show that an n-vertex hypergraph with no r-regular subgraph has at most 2n-1+r-2 edges. We conjecture that if n>r, then every n-vertex hypergraph with no r-regular subgraph having the maximum number of edges contains a full star, meaning 2n-1 distinct edges containing a common vertex. We prove this conjecture for n ≥ 425. This is joint work with Alexandr V. Kostochka.

Department Awards Ceremony
4:00 pm   in 314 A&B Illini Union,  Tuesday, April 19, 2011
 Del Edit Copy
Submitted by seminar.
 Department Awards CeremonyAbstract: The Department of Mathematics Awards Ceremony will be held at 4 p.m. in Room 314 A&B Illini Union. Awards will be presented to undergraduate students, graduate students, faculty and staff. Please join us for a reception immediately following the presentation of awards.