All Seminars
| Title: Contact geometry, open books and monodromy |
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| Colloquium: Topology |
| Speaker: John Etnyre of Georgia Tech |
| Contact: Aaron Abrams, abrams@mathcs.emory.edu |
| Date: 2009-04-06 at 3:00PM |
| Venue: W306 |
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| Abstract: Recall that an open book decomposition of a 3-manifold M is a link L in M whose complement fibers over the circle with fiber a Seifert surface for L. Giroux's correspondence relates open book decompositions of a manifold M to contact structures on M. This correspondence has been fundamental to our understanding of contact geometry. An intriguing question raised by this correspondence is how geometric properties of a contact structure are reflected in the monodromy map describing the open book decomposition. In this talk I will show that there are several interesting monoids in the mapping class group that are related to various properties of a contact structure (like being Stein fillable, weakly fillable, . . .). I will also show that there are open book decompositions of Stein fillable contact structures whose monodromy cannot be factored as a product of positive Dehn twists. This is joint work with Jeremy Van Horn-Morris and Ken Baker. |
| Title: Density of isoperimetric spectra |
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| Colloquium: Topology |
| Speaker: Noel Brady of University of Oklahoma |
| Contact: Aaron Abrams, abrams@mathcs.emory.edu |
| Date: 2009-04-06 at 4:00PM |
| Venue: W306 |
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| Abstract: |
| Title: Digital Identity Management and Protection |
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| Seminar: Computer Science |
| Speaker: Elisa Bertino of CS Department, CERIAS, Purdue University |
| Contact: Li Xiong, lxiong@mathcs.emory.edu |
| Date: 2009-04-03 at 3:00PM |
| Venue: MSC W301 |
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| Abstract: \small Digital identity management (DIM) has emerged as a critical foundation for supporting successful interaction in today's globally interconnected society. It is crucial not only for the conduct of business and government but also for a large and growing body of electronic or online social interactions. Digital identity management is usually coupled with the notion of federation. The goal of federations is to provide users with protected environments to federate identities by the proper management of identity attributes. Federations provide a controlled method by which federation members can provide more integrated and complete services to a qualified group of individuals within certain sets of business transactions. By controlling the scope of access to participating sites, and by enabling secure, cross-domain transmission of user's personal information, federations can make the perpetration of identity frauds more difficult, as well as reduce their frequency, and their potential impact. In this talk we will first discuss basic digital identity concepts and requirements towards DIM solutions and we will overview relevant initiatives currently undergoing in academia and industry. We will then focus on the problem of identity theft and discuss an initial solution to the problem of establishing and protecting digital identity.\\ \\* \textbf{Biography:} Elisa Bertino is professor of Computer Science at Purdue University and serves as Research Director of the Center for Education and Research in Information Assurance and Security (CERIAS). Previously she was a faculty member at Department of Computer Science and Communication of the University of Milan where she directed the DB and SEC laboratory. She has been a visiting researcher at the IBM Research Laboratory (now Almaden) in San Jose, at the Microelectronics and Computer Technology Corporation, at Rutgers University, at Telcordia Technologies. Elisa Bertino is a Fellow member of IEEE and a Fellow member of ACM. She received the 2002 IEEE Computer Society Technical Achievement Award for "For outstanding contributions to database systems and database security and advanced data management systems" and the 2005 IEEE Computer Society Tsutomu Kanai Award "For pioneering and innovative research contributions to secure distributed systems". \\ |
| Title: On Graphs with a Given Endomorphism Monoid |
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| Defense: Dissertation |
| Speaker: Benjamin Shemmer of Emory University |
| Contact: Benji Shemmer, bshemmer@emory.edu |
| Date: 2009-04-02 at 4:00PM |
| Venue: MSC W201 |
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| Abstract: Hedlin and Pultr proved that for any monoid M there exists a graph G with endomorphism monoid isomorphic to M. We will give a construction G(M) for a graph with prescribed endomorphism monoid M. Using this construction we derive bounds on the minimum number of vertices and edges required to produce a graph with a given endomorphism monoid for various classes of finite monoids. |
| Title: Patching Brauer Groups |
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| Seminar: Algebra |
| Speaker: Feng Chen of Emory University |
| Contact: Feng Chen (Emory), fchen@emory.edu |
| Date: 2009-03-31 at 4:00PM |
| Venue: MSC W303 |
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| Abstract: |
| Title: Bidirectional Wave Propagation in the Human Arterial Tree |
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| Seminar: Numerical Analysis and Scientific Computing |
| Speaker: Radu C. Cascaval of University of Colorado at Colorado Springs |
| Contact: Alessandro Veneziani, ale@mathcs.emory.edu |
| Date: 2009-03-27 at 3:00PM |
| Venue: MSC W303 |
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| Abstract: We describe a nonlinear model for the propagation of the pressure and flow velocity waves in the peripheral circulation, which is based on a Boussinesq-type system. The key ingredient is the inclusion of dispersive effects (amplitude-dependent speeds of propagation) in addition to the nonlinear effects. We discuss the formation and propagation of the transmitted and reflected waves at bifurcations and terminal ends. The timing of the reflections as well as the different speeds of the reflected waves are particularly relevant in view of the complex geometry of the peripheral circulation. The advantage of this analysis in the time domain, compared with linear impedance models, is that it applies for non-periodic flows and also allows the direct implementation of accurate time-dependent controls, such as those exhibited in the peripheral circulation. We discuss an application of this model on the study of the latencies measured experimentally during rest and dynamical changes in the cardiovascular system. |
| Title: Killing forms of Lie algebras |
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| Dissertation defense: Algebra |
| Speaker: Audrey Malagon of Emory University |
| Contact: Skip Garibaldi, skip@mathcs.emory.edu |
| Date: 2009-03-25 at 4:00PM |
| Venue: MSC W201 |
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| Abstract: One approach to the problem of classifying Lie Algebras is to find invariants. One such invariant is the Killing form. In this talk I will give a formula for computing the Killing form of an isotropic Lie algebra defined over an arbitrary field of characteristic zero, based on the Killing form of a subalgebra containing its anisotropic kernel. I will then explicitly compute the Killing form for several Lie algebras of exceptional type and give a general formula for the Killing form of all inner type Lie algebras of type E6, including the anisotropic ones. |
| Title: Towards Contextual Text Mining |
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| Seminar: Computer Science |
| Speaker: Qiaozhu Mei of University of Illinois at Urbana-Champaign |
| Contact: Eugene Agichtein, eugene@mathcs.emory.edu |
| Date: 2009-03-24 at 11:00AM |
| Venue: W302 |
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| Abstract: Text is generally associated with all kinds of contextual information. Contextual information can be explicit, such as the time and the location where a blog article is written, and the author(s) of a biomedical publication, or implicit, such as the positive or negative sentiment that an author had when he/she wrote a product review; there may also be complex context such as the social network of the authors. Many applications require analysis of patterns of topics over different contexts. For instance, analysis of search logs in the context of users can reveal how we can improve the quality of a search engine by optimizing the search results according to particular users, while analysis of text in the context of a social network can facilitate discovery of more meaningful topical communities. Since contextual information affects significantly the choices of topics and words made by authors, in general, it is very important to incorporate it in analyzing and mining text data. In this talk, I will present a new paradigm of text mining, called contextual text mining, where context is treated as a "first-class citizen." I will introduce general ways of modeling and analyzing various kinds of context in text, including simple context, implicit context, and complex context, in the framework of probabilistic language models. I will show the effectiveness of these general contextual text mining techniques with sample applications in web search and social network analysis. Biosketch: Qiaozhu Mei is a Ph.D. candidate of Department of Computer Science at the University of Illinois at Urbana-Champaign. He has broad research interests in text information management, especially text mining and information retrieval with probabilistic models. He has published extensively in these areas, and has received the Best Student Paper Runner-Up Awards of ACM KDD 2006 and ACM KDD 2007. He is also one of the five recipients of the inaugural Yahoo! Ph.D. Student Fellowship. |
| Title: Representation theory: a brief introduction from the sl(n) perspective |
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| Seminar: Algebra |
| Speaker: Julie Beier of Mercer University |
| Contact: Skip Garibaldi, skip@mathcs.emory.edu |
| Date: 2009-03-24 at 3:00PM |
| Venue: MSC W303 |
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| Abstract: Representation theory can be simply defined as the study of the ways a group acts on a vector space. A large piece of this process involves understanding weight spaces, particularly irreducible highest weight spaces. We will explore weight spaces of irreducible representations by looking at $sl(n, \mathbf{C})$, $U_q(sl(n))$ and $U_q(\widehat{sl}(n))$. As the structure of the space becomes more complicated we utilize different combinatorics to understand these irreducible, highest weight spaces. |
| Title: Signal Processing Approach To Obtain A Direct Multi-grid Solver |
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| Seminar: Numerical Analysis and Scientific Computing |
| Speaker: Pablo Navarrete of University of Chile, Department of Electrical Engineering |
| Contact: Jim Nagy, nagy@mathcs.emory.edu |
| Date: 2009-03-20 at 3:00PM |
| Venue: W306 |
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| Abstract: Modifications of the conventional muti-grid algorithm are explored to avoid the use of smoothing iterations. In the full multi-grid algorithm, classical smoothing iterations (e.g. Gauss-Seidel) reduce high-frequency components of the error and a coarse-grid approach reduces the low-frequency components of the error. The problem here is that two methods with different structures are being combined, which introduces additional complexity in the convergence analysis of multi-grid methods. Then, the idea is to avoid the use of smoothing iterations by using different inter-grid configurations. In an analogy with perfect reconstruction filters, a configuration of inter-grid operators is found such that the approximation error is completely cancelled after one iteration of the algorithm. The main assumption for this configuration to work is a particular aliasing pattern in the eigen-vectors of the linear system. Examples and simulations are presented to evaluate the performance of the new algorithm. |