## Seminars and Colloquia by Series

### School of Mathematics Faculty Meeting

Series
Other Talks
Time
Thursday, January 28, 2010 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 249
Speaker
Provost Gary SchusterPresident&amp;#039;s Office, Georgia Tech

### Southeast Geometry Seminar

Series
Other Talks
Time
Monday, December 7, 2009 - 08:00 for 8 hours (full day)
Location
University of Alabama, Birmingham
Speaker
Southeast Geometry SeminarUniversity of Alabama, Birmingham

The Southeast Geometry Seminar is a series of semiannual one-day events focusing on geometric analysis. These events are hosted in rotation by the following institutions:

• The University of Alabama at Birmingham
• The Georgia Institute of Technology
• Emory University
• The University of Tennessee Knoxville

The following five speakers will give presentations on topics that include geometric analysis, and related fields, such as partial differential equations, general relativity, and geometric topology.

• Natasa Sesum (U Penn)
• Alexandru Ionescu (U Wisconsin)
• Sergiu Klainerman (Princeton U)
• Alex Freire (U Tennessee Knoxville)
• Christian Hainzl (UAB)

A poster session will be hosted. There will also be an evening public lecture by plenary speaker Sergiu Klainerman entitled The Mathematical Magic of Black Holes.

Series
Other Talks
Time
Friday, December 4, 2009 - 15:00 for 1.5 hours (actually 80 minutes)
Location
Skiles 168
Speaker
Michelle Delcourt and Leo ChenSchool of Mathematics, Georgia Tech

Leo Chen: The Shape and Stability of a Flexible Sheet in a von Karman Vortex Street

Michelle Delcourt: Dessin and Manturov bracket shuffles
In this talk we will explore the connections between knot theory and combinatorics. Links are related to Grothendieck's dessins d'enfants. Cartographic one-vertex dessins can be represented by chord diagrams. The diagrams can be recorded as "words" using a finite alphabet (k-bracket parenthesis system). Many combinatorial objects are related to these Manturov bracket structures.

### Cohomology and the Riemann-Roch theorem

Series
Other Talks
Time
Wednesday, December 2, 2009 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Kangkang WangSchool of Mathematics, Georgia Tech
We will present a sheaf-theoretic proof of the Riemann-Roch theorem for projective nonsingular curves.

### Hilbert polynomials and cohomology

Series
Other Talks
Time
Wednesday, November 25, 2009 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Matt BakerSchool of Mathematics, Georgia Tech
We will state Serre's fundamental finiteness and vanishing results for the cohomology of coherent sheaves on a projective algebraic variety. As an application, we'll prove that the constant term of the Hilbert Polynomial does not depend on the projective embedding, a fact which is hard to understand using classical (non-cohomological) methods.

### Grothendieck Topologies

Series
Other Talks
Time
Wednesday, November 18, 2009 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Doug UlmerGa Tech
In the 60s, Grothendieck had the remarkable idea of introducing a new kind of topology where open coverings of X are no longer collections of subsets of X, but rather certain maps from other spaces to X.  I will give some examples to show why this is reasonable and what one can do with it.

### Derived functors and Cech cohomology

Series
Other Talks
Time
Wednesday, November 11, 2009 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Farbod ShokriehGa Tech
We will show that the construction of derived functors satisfy the required universal property.I will then show that, for any ringed space, the abelian category of all sheaves of Modules has enough injectives. We achieve this by first characterizing injective abelian groups (Baer's theorem).The relation with Cech cohomology will also be studied. In particular, I will show that the first Cech and Grothendieck sheaf cohomology groups are isomorphic for any topological space (without using spectral sequences).

### Small noise limit for dynamics near unstable critical points (Oral Comprehensive Exam).

Series
Other Talks
Time
Friday, November 6, 2009 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 154
Speaker
We consider the Stochastic Differential Equation $dX_\epsilon=b(X_\epsilon)dt + \epsilon dW$ . Given a domain D, we study how the exit time and the distribution of the process at the time it exits D behave as \epsilon goes to 0. In particular, we cover the case in which the unperturbed system $\frac{d}{dt}x=b(x)$ has a unique fixed point of the hyperbolic type. We will illustrate how the behavior of the system is in the linear case. We will remark how our results give improvements to the study of systems admitting heteroclinic or homoclinic connections. We will outline the general proof in two dimensions that requires normal form theory from differential equations. For higher dimensions, we introduce a new kind of non-smooth stochastic calculus.

### Derived functors and sheaf cohomology

Series
Other Talks
Time
Wednesday, November 4, 2009 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Farbod ShokriehGa Tech
We will continue the study of derived functors between abelian categories. I will show why injective objects are needed for the construction. I will then show that, for any ringed space, the abelian category of all sheaves of Modules has enough injectives. The relation with Cech cohomology will also be studied.

### Joint ACO/DOS - Approximability of Combinatorial Problems with Multi-agent Submodular Cost Functions

Series
Other Talks
Time
Wednesday, October 28, 2009 - 11:00 for 1 hour (actually 50 minutes)
Location
ISyE Executive Classroom
Speaker
Pushkar TripathiACO, Computing Science and Systems, Georgia Tech