Seminar Calendar
for Differential Geometry events the next 12 months of Saturday, August 1, 2009.

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More information on this calendar program is available.
Questions regarding events or the calendar should be directed to Tori Corkery. 
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Tuesday, September 22, 2009

Differential Geometry Seminar
1:00 pm   in 243 Altgeld Hall,  Tuesday, September 22, 2009
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Submitted by ekerman.
Isidora Milin (UIUC Math)
Orderability of Contactomorphism Groups of Lens Spaces
Abstract: A contact isotopy of a contact manifold is "positive" if during it, each point of the manifold moves in a positively transverse direction to the contact hyperplane distribution. The question of whether this notion induces a partial order on the universal cover of the identity component of the contactomorphism group - whether the contact manifold is "orderable" - turns out to be sensitive to the topology of the contact manifold, and is related to nonsqueezing phenomena in contact geometry, as studied by Eliashberg, Kim and Polterovich. I will begin by explaining this relation, and then describe a version of contact homology for domains that enables us to detect relevant contact nonsqueezings. This will be illustrated by standard contact sphere (not orderable) and lens spaces (orderable).

Friday, October 9, 2009

Women in Mathematics Seminar
1:00 pm   in 141 Altgeld Hall,  Friday, October 9, 2009
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Submitted by akwiatk2.
Alexandra Seceleanu (UIUC Math)
Weak Lefschetz Property - a computational approach
Abstract: I will begin by introducing the algebraic counterpart of the famous Lefschetz Property in differential geometry. Then we shall explore some of the tools that are available for algebraists to study the Weak Lefschetz property. I will show how to completely solve the problem in a particular case. Time permitting, I will illustrate my talk with computations using computer algebra software. This talk will be easily accessible to non-specialists.

Tuesday, October 27, 2009

Differential Geometry Seminar
1:00 pm   in 243 Altgeld Hall,  Tuesday, October 27, 2009
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Submitted by ekerman.
Rebecca Goldin (George Mason University)
Full Orbifold K-theory of Abelian Symplectic Quotients
Abstract: We will begin with a review of one way in which orbifolds arise, which is via the symplectic of a Hamiltonian T-space, where T is an abelian Lie group. Our goal is to describe the full orbifold K-theory for this class of spaces. Toward that purpose, we introduce the *inertial K-theory* of a Hamiltonian T-space M and show that it surjects as a ring onto the full orbifold K-theory of the symplectic quotient, denoted M//T (at a regular value). This research essentially involves two ingredients: The fact (due to M. Harada and G. Landweber) that equivariant K-theory of M maps surjectivity onto the K-theory of M//T, and the invention of a fancy product on the inertial K-theory of M, so that it surjects onto the full orbifold K-theory of M//T. These ideas are based on a similar (though rational) story in cohomology which we will also discuss. This is joint work with T. Holm, M. Harada, and T. Kimura.

Tuesday, November 3, 2009

Differential Geometry Seminar
1:00 pm   in 243 Altgeld Hall,  Tuesday, November 3, 2009
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Submitted by clein.
Eriko Hironaka (FSU & Harvard)
Small dilatation mapping classes from the simplest pseudo-Anosov braid
Abstract: By a recent theorem of Farb, Leininger and Margalit, the set of 3-manifolds `realizing' mapping classes with small dilatation (compared to Euler characteristic) is finite. We show that all known minimal dilatation mapping classes for small genus are realized on the complement of Rolfsen's 6_2^2 link in S^3, and discuss the plausibility that minimal dilatation mapping classes for all genus are realized on this manifold.

Thursday, November 19, 2009

Differential Geometry Seminar
3:00 pm   in 347 Altgeld Hall,  Thursday, November 19, 2009
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Submitted by clein.
Ken Bromberg (U. Utah)
The asymptotic dimension of the mapping class group
Abstract: We will show that the mapping class group has finite asymptotic dimension. A key piece of the proof is the construction of a quasi-tree that mapping class acts on. This construction works in a quite general setting for groups that have some aspect of negative curvature. We will describe this construction and explain how it relates to the asymptotic dimension of the mapping class group. This is joint work with K. Fujiwara and M. Bestvina.