All Seminars

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Title: Differential Privacy: What Does It Mean and What Can Be Achieved?
Seminar: Computer Science
Speaker: Dr. Ninghui Li of Purdue University
Contact: Li Xiong, lxiong@emory.edu
Date: 2016-03-25 at 3:00PM
Venue: W301
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Abstract:
Over the last decade, differential privacy (DP) has emerged as the standard privacy notion for research in privacy-preserving data analysis and publishing. However, there is an ongoing debate about the meaning and value of DP. Some hail that the notion of DP offers strong privacy protection regardless of the adversary's prior knowledge while enabling all kinds of data analysis. Others offer criticisms regarding DP's privacy guarantee and utility limitations. In this talk, we focus on two issues. One is what does DP mean? More precisely, under what condition(s), the notion of DP delivers the promised privacy guarantee? We show that DP is based on the following Personal Data Principle: "Data privacy means giving an individual control over his or her personal data. Privacy does not mean that no information about the individual is learned, or no harm is done to an individual. Enforcing the latter is infeasible and unreasonable.'' Furthermore, the question of when DP is adequate is not just a technical question and depends on legal and ethical considerations. In the second part of the talk, we give a survey of the state of the art in publishing a summary of a relational dataset, ranging from publishing histograms for one-dimensional and two-dimensional datasets, to answering marginal queries for datasets with dozens of dimensions, and finally to finding frequent itemsets in transactional datasets with thousands or more of dimensions. Brief Bio: Ninghui Li is a Professor of Computer Science at Purdue University, where he has been a faculty member since 2003. His research interests are in security and privacy. He has published over 130 referred papers in these areas. Prof. Li is current on the editorial boards of Journal of Computer Security (JCS) and ACM Transactions on Internet Technology (TOIT). He was on the editorial board of IEEE Transactions on Dependable and Secure Computing (TDSC) from 2011 to 2015 and the VLDB Journal from 2007 to 2013. He recently served as Program Chair of 2014 and 2015 ACM Conference on Computer and Communications Security (CCS), ACM's flagship conference in the field of security and privacy.
Title: Hasse principle for Hermitian spaces
Defense: Dissertation
Speaker: Zhengyao Wu of Emory University
Contact: Zhengyao Wu, zwu22@emory.edu
Date: 2016-03-24 at 4:00PM
Venue: W302
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Abstract:
This dissertation provides three results: (1) A Hasse principle for rational points of projective homogeneous spaces under unitary or special unitary groups associated to hermitian or skew hermitian spaces over function fields of p-adic curves; (2) A Springer-type theorem for isotropy of hermitian spaces over odd degree field extensions of function fields of p-adic curves; (3) Exact values of Hermitian u-invariants of quaternion or biquaternion algebras over function fields of p-adic curves.
Title: Vanishing and identities of conformal blocks divisors.
Seminar: Algebra
Speaker: Angela Gibney of UGA
Contact: David Zureick-Brown, dzb@mathcs.emory.edu
Date: 2016-03-22 at 4:00PM
Venue: W304
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Abstract:
In this talk I will give a tour of recent results and open problems about vector bundles of conformal blocks on the moduli space of curves. I will discuss how these results fit into the context of some of the open problems about the binational geometry of the moduli space.
Title: Torsion subgroups of rational elliptic curves over the compositum of all cubic fields.
Seminar: Algebra
Speaker: Drew Sutherland of MIT
Contact: David Zureick-Brown, dab@mathcs.emory.edu
Date: 2016-03-18 at 4:00PM
Venue: W303
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Abstract:
Let E/Q be an elliptic curve and let Q(3^infty) denote the compositum of all cubic extensions of Q. While the group E(3^infty) is not finitely generated, one can show that its torsion subgroup is finite; this holds more generally for any Galois extension of Q that contains only finitely many roots of unity. I will describe joint work with Daniels, Lozano-Robledo, and Najman, in which we obtain a complete classification of the 20 torsion subgroups that can and do occur, along with an explicit description of the elliptic curves E/Q that realize each possibility (up to twists). This is achieved by determining the rational points on a corresponding set of modular curves and relies on several recent results related to the mod-n Galois representations attached to elliptic curves over Q.
Title: Gerbes, twisted sheaves and their relation to the Brauer group(s) of schemes
Seminar: Algebra
Speaker: Max Lieblich of University of Washington
Contact: Raman Parimala, parimala@mathcs.emory.edu
Date: 2016-03-17 at 1:00PM
Venue: E406
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Abstract:
TBA
Title: Gerbes, twisted sheaves and their relation to the Brauer group(s) of schemes
Seminar: Algebra
Speaker: Max Lieblich of University of Washington
Contact: Raman Parimala, parimala@mathcs.emory.edu
Date: 2016-03-16 at 1:00PM
Venue: E408
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Abstract:
TBA
Title: Integral points on groupic varieties (work of Yang Cao and Fei Xu)
Seminar: Algebra
Speaker: J.L. Colliot-Thelene of CNRS et Universite Paris-Sud
Contact: David Zureick-Brown, dab@mathcs.emory.edu
Date: 2016-03-15 at 4:00PM
Venue: W304
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Abstract:
Summary : Let G be a connected linear algebraic group over a field k. By definition, a groupic G-variety X over k is a smooth (left) G-variety with a dense open set isomorphic to G with its (left) action on itself. Let X be a groupic G-variety over a number field. Under a suitable noncompactness hypothesis for the simple factors of the semisimple part of G at the archimedean places, Cao and Xu show that the Brauer-Manin obstruction is the only obstruction to strong approximation for X off the archimedean places. The proof builds upon the case X=G (handled in earlier papers by Xu and the speaker, Harari, Demarche). The toric case (G is a torus) was already handled in a previous paper by Cao and Xu. For X projective, the statement is a weak approximation result and the theorem has been known for a long time (Sansuc).. The proof of the strong approximation result for an arbitrary groupic G-variety X involves novel arguments, both geometric and arithmetic.
Title: Genus one curves in Severi-Brauer Varieties.
Seminar: Algebra
Speaker: David Saltman of IDA
Contact: David Zureick-Brown, dzb@mathcs.emory.edu
Date: 2016-03-15 at 5:00PM
Venue: W304
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Abstract:
Let A/F be a division algebra of degree 3, and X its Severi-Brauer variety which is a form of the projective plane. The linear system of cubic curves is defined on X, and so we can let C \subset X be one such. If C is a nonsingular such curve, then C is a genus one curve with Jacobian E, an elliptic curve. The question we address is the one asked by Asher Auel, namely, which E arise. We give an answer that depends on the structure of A.
Title: Some Ramsey-type Theorems
Defense: Dissertation
Speaker: Troy Retter of Emory University
Contact: Troy Retter, tretter@emory.edu
Date: 2016-03-02 at 11:30AM
Venue: E408
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Abstract:
See downloadable flyer.
Title: Beyond the moduli of marked rational curves
Seminar: Algebra
Speaker: Patricio Gallardo of UGA
Contact: David Zureick-Brown, dzb@mathcs.emory.edu
Date: 2016-03-01 at 4:00PM
Venue: W304
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Abstract:
We describe several generalizations of the moduli space of marked rational curves, their combinatorial structure and construction methods. In particular, we report joint work with Noah Giansiracusa in which we revisit the smooth configuration space compactifying n distinct points in affine space up to translation and homothety. I will also report joint work with Kenny Ascher in understanding a good locus inside the moduli space of weighted line arrangements constructed by V. Alexeev.