All Seminars
| Title: Field invariants via refinements to patching |
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| Seminar: Algebra |
| Speaker: David Harbater of UPenn |
| Contact: David Zureick-Brown, dzb@mathcs.emory.edu |
| Date: 2014-05-13 at 3:00PM |
| Venue: W306 |
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| Abstract: We consider fraction fields of complete two-dimensional domains, and obtain their u-invariant and period-index bound. This work, which is joint with Julia Hartmann and Daniel Krashen, builds on the method of patching, and introduces a new notion of refinement. Using that, we obtain local-global principles for quadratic forms and central simple algebras over the fields we consider, and also our results on numerical invariants of fields. |
| Title: The set of non-n-th powers in a number field is Diophantine |
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| Seminar: Algebra |
| Speaker: Jean-Louis Colliot-Thelene of Universite Paris-Sud |
| Contact: David Zureick-Brown, dzb@mathcs.emory.edu |
| Date: 2014-05-08 at 3:00PM |
| Venue: W306 |
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| Abstract: In a joint work with J. Van Geel, we prove: For any natural integer n, the complement of the set of n-th powers in a number field k is the image of the set of k-rational points of some k-variety X under some k-morphism from X to the affine line. For n=2, this is a result of B. Poonen (2009). His proof uses local-global theorems (CT, Coray, Sansuc, 1980) for rational points on Ch\^{a}telet surfaces. Our proof for n arbitrary combines Poonen’s method and local-global theorems (CT, Swinnerton-Dyer, Skorobogatov, 1994, 1998) for zero-cycles on higher dimensional analogues of Ch\^{a}telet surfaces. |
| Title: Log canonical and F-pure thresholds and ordinary reduction |
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| Seminar: Algebra |
| Speaker: Lance Edward Miller of University of Arkansas |
| Contact: David Zureick-Brown, dzb@mathcs.emory.edu |
| Date: 2014-05-06 at 4:00PM |
| Venue: W306 |
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| Abstract: The F-pure threshold of a variety in characteristic p > 0 is a rational number which measure of its singularities near the origin. It is intimately connected to birrational invariants of complex varieties such as the log canonical threshold through reduction mod p. The agreement of these two invariants is also deeply connected to ordinary (in the sense of Bloch-Kato) reduction as can already been seen clearly in the case of elliptic curves. This talk introduces these thresholds and their connections and explores a special cases where agreement can be shown purely in using algebraic methods. |
| Title: On Stabilization of Classical Groups |
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| Seminar: Algebra |
| Speaker: Rabeya Basu of IISER, Pune |
| Contact: David Zureick-Brown, dzb@mathcs.emory.edu |
| Date: 2014-05-02 at 3:00PM |
| Venue: W304 |
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| Abstract: The $K_1$ stabilization of general linear groups is one of the problem related to Serre's problem on projective modules. It was first studied by Bass---Milnor---Serre during mid-sixties. They showed that the surjective bound is d+1, where d is the Krull dimension of the base ring, and conjectured that the injective bound is d+2. Shortly after that it was proved by L.N. Vaserstein. Later we see analog results for other classical groups in the work of A. Suslin, V. Kopeiko, Vaserstien, A. Bak, G. Tang, V. Petrov, W. vander Kallen et al. including the recent break through work by J.Fasel, R.A. Rao and R.G. Swan. In this talk we shall discuss results on injective stabilization for a big class of classical grou |
| Title: Transversality defect of two lagrangians and ternary index. Application: Formulas of (non) additivity of signatures and of linking forms |
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| Seminar: Algebra |
| Speaker: Jean Barge of Ecole polytechnique |
| Contact: David Zureick-Brown, dzb@mathcs.emory.edu |
| Date: 2014-04-29 at 4:00PM |
| Venue: W302 |
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| Abstract: (This is a common work with Jean Lannes) To a pair of lagrangians in a symplectic space, we associate a symetric bilinear form well defined up to the addition of non-degenerate forms and which is itself non-degenerate if and only if the two lagrangians are transversal. To a triple of lagrangians, we associate a ternary index which is a raffinement of the Leray-Kashiwara index and which generalizes for any (commutative) ring the index defined by Wall for fields. We will explain how these two invariants can be used to compute signatures and linking forms of manifolds obtained by gluing. |
| Title: Online Social Dynamics and Wellbeing |
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| Seminar: Computer Science |
| Speaker: Munmun De Choudhury of Georgia Institute of Technology |
| Contact: Eugene Agichtein, eugene@mathcs.emory.edu |
| Date: 2014-04-25 at 3:00PM |
| Venue: MSC W301 |
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| Abstract: Social networks, Facebook and Twitter are continually creating rich repositories of information relating to our activities, emotion and linguistic expression. By leveraging such trails of data and developing machine learning models, we can not only elucidate core aspects of human behavior, but can begin to solve a vista of problems relating to our health behaviors, which have traditionally been challenging. In this talk I will discuss the harnessing of social media in reasoning about behavioral health concerns experienced by populations around major disruptions in life. In a first study, I will present analyses and computational models that make automated inferences about the status and dynamics of postpartum depression in new mothers via postings made on Twitter and Facebook. In a second study, we will examine the affective responses in Twitter experienced by communities in Mexico embroiled in protracted armed conflict and how they might indicate desensitization to violence. Broadly, I will discuss how this new line of research bears potential in informing the design of early-warning systems and interventions to help individuals and policymakers be more proactive about health and wellbeing.\\ \\ Bio:\\ \\ Munmun De Choudhury is currently an assistant professor at the School of Interactive Computing, Georgia Tech. Munmun’s research interests are in computational social science, with a specific focus on reasoning about our health behaviors from social digital footprints. She has been a recipient of the Grace Hopper Scholarship, recognized with an IBM Emergent Leaders in Multimedia award, and recipient of ACM SIGCHI 2014 best paper award and ACM SIGCHI honorable mention awards in 2012 and 2013. Earlier, Munmun was a postdoctoral researcher at Microsoft Research, a research fellow at Rutgers, and obtained a PhD in Computer Science from Arizona State University in 2011. |
| Title: Truth Is Stranger Than Fiction: A Look At Some Improbabilities |
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| Seminar: N/A |
| Speaker: Dr. Rick Durrett of Duke University |
| Contact: TBA |
| Date: 2014-04-24 at 4:00PM |
| Venue: MSC E208 |
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| Abstract: Probability is full of surprises and paradoxes, most of which result from doing the calculation incorrectly. We will illustrate this using some familiar old stories and new ones: the Monty Hall problem, cognitive dissonance in Monkeys, the birthday problem, lottery coincidences, the sad story of Sally Clark, the 2012 election, and Warren Buffet’s bracket challenge. |
| Title: Rational connectivity and analytic contractibility |
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| Seminar: Algebra |
| Speaker: Tyler Foster of University of Michigan |
| Contact: David Zureick-Brown, dzb@mathcs.emory.edu |
| Date: 2014-04-22 at 5:00PM |
| Venue: W302 |
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| Abstract: Let K be an algebraically closed field of characteristic 0. A smooth projective K-variety X is rationally connected if each pair of points in X is connected by a rational curve inside X. Over a non-archimedean field K, each of these rational curves becomes a contractible Berkovich space, so X has lots of contractible subvarieties. In fact more is true: In this talk, I will discuss recent work with Morgan Brown in which we prove that over the non-archimedean field K=C((t)), the Berkovich space associated to any smooth projective, rationally connected variety X is contractible. |
| Title: What is Ramsey-equivalent to a clique? |
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| Seminar: Combinatorics |
| Speaker: Andrey Grinshpun of Massachusetts Institute of Technology |
| Contact: Dwight Duffus, dwight@mathcs.emory.edu |
| Date: 2014-04-21 at 4:00PM |
| Venue: W306 |
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| Abstract: |
| Title: Image Recognition of Coronary Stents for Automatic Construction of Patient Specific Models |
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| Honors Thesis: Applied Mathematics |
| Speaker: Shannon Buckley of Emory University |
| Contact: TBA |
| Date: 2014-04-16 at 1:00PM |
| Venue: MSC E408 |
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| Abstract: Professor Veneziani and his team of graduate students have been working on the problem of modeling the effects that cardiovascular disease and the medical procedures employed to cure it have on the fluid dynamic process of the cardiovascular system. One of the newer solutions to this pressing disease is to insert a medical structure, called a stent, into the artery where a blockage is occurring. The modeling of this procedure requires the creation of a 3D model of the stent, which is then used in the algorithms. For real patients this data has previously been collected by manually recording the locations of the stent structures found in arthroscopic images of the patient’s arteries. To speed up this data collection process and provide more accurate data, we have created a MATLAB algorithm that uses image recognition software to automatically identify stent structures in the arthroscopic images and record their positions in the artery. |