All Seminars

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Title: Secure and Privacy-Preserving Distributed Data Release
Defense: Dissertation
Speaker: Slawomir Goryczka of Emory University
Contact: Vaidy Sunderam, vss@emory.edu
Date: 2014-05-13 at 11:00AM
Venue: W301
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Abstract:
The rapidly increasing prevalence of distributed data-driven applications has highlighted security and privacy issues in storing and processing sensitive data. Although manipulating raw data may violate privacy of their owners, different techniques of preparing and using privacy-preserving data descriptions can be still used. It remains a challenge, however, to ensure that adapted and new solutions are efficient, secure, and preserve privacy of data owners without disclosing confidentiality of data providers.\\ \\ The dissertation proposes a new notion of $m$-privacy that addresses the challenges when data providers may act as adversaries. To verify if such adversaries are capable of breaching privacy, we introduce a few different strategies and an adaptive algorithm to select and run the most efficient approach. In addition, we designed an algorithm to anonymize data, such that its results are $m$-private, i.e., knowing the results would not help any $m$ colluding parties in their attacks. All verification and anonymization algorithms have been implemented to be run in distributed environments by a trusted third party.\\ \\ For settings without a trusted third party, we introduce new secure multiparty computation protocols that implement centralized $m$-privacy verification and anonymization algorithms. For each protocol, we provedits security, analyzed its communication complexity, and evaluated its overall performance for various settings.\\ \\ The dissertation also describes a new algorithm to build differentially private histograms for records with customized privacy levels. The algorithm has two data partitioning phases (privacy-driven and data-driven). In addition, we adapted a v-optimal partitioning algorithm to be used with differential privacy, and experimentally evaluated their performance. \\ \\ Finally, the dissertation presents a new differential privacy mechanism that achieves collusion resistance in distributed environments with small overhead. We also defined an enhanced fault tolerant secure scheme (EFT), which can be used to design a variety of secure multiparty aggregation operations, and we employed it to implement our differential privacy mechanism in distributed environments. Both, the privacy mechanism and the EFT scheme have been extensively analyzed and experimentally evaluated.
Title: Field invariants via refinements to patching
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
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
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
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
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
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: 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
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
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?
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:
TBA