All Seminars

Title: Counting Substructures
Seminar: Combinatorics
Speaker: Dhruv Mubayi of The University of Illinois, Chicago
Contact: Dwight Duffus, dwight@mathcs.emory.edu
Date: 2009-09-04 at 4:00PM
Venue: W306
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Abstract:
For various (hyper)graphs F, we give sharp lower bounds on the number of copies of F in a (hyper)graph with a prescribed number of vertices and edges. Our results extend those of Rademacher, Erdos and Lovasz-Simonovits for graphs and of Bollobas, Frankl, Furedi, Keevash, Pikhurko, Simonovits and Sudakov for hypergraphs. The proofs use the hypergraph removal lemma and stability results for the corresponding Turan problem proved by the above authors.
Title: Bertrand's postulate and subgroup growth
Seminar: Algebra
Speaker: Ben McReynolds of University of Chicago
Contact: Skip Garibaldi, skip@mathcs.emory.edu
Date: 2009-09-01 at 4:00PM
Venue: MSC W303
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Abstract:
In this talk, I will discuss an extension of Bertrand's postulate on gaps between primes to finitely generated linear group that provides an interesting variant of subgroup growth. This is also connected with the residual average of a residually finite group, a variant which quantifies residual finiteness. This talk will largely be accessible to a general audience.
Title: Model to Predict I/O For SPARQL Queries Using the TripleT Index
Master's Thesis Defense: Computer Science
Speaker: Kanwei Li of Emory University
Contact: Kanwei Li, kli@gmail.com
Date: 2009-07-29 at 4:00PM
Venue: MSC E408
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Abstract:
Title: Hamiltonicity and Pancyclicity of 4-connected, Claw- and Net-free Graphs
Defense: Dissertation
Speaker: Silke Gehrke of Emory University
Contact: Silke Gehrke, sgehrke@emory.edu
Date: 2009-05-29 at 4:00PM
Venue: MSC W301
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Abstract:
A well-known conjecture by Manton Matthews and David Sumner states, that every $4$-connected $K_{1,3}$ -free graph is hamiltonian. The conjecture itself is still wide open, but several special cases have been shown so far. We will show, that if a graph is $4$-connected and $\{K_{1,3}$, $N\}$- free, where $N =$ $N(i, j, k)$, with $i + j + k = 5$ and $i$, $j$, $k \geq 0$, the graph is pancyclic.
Title: Nearly Perfect Packings
Defense: Dissertation
Speaker: Daniel Martin of Emory University
Contact: Daniel Martin, dmarti8@emory.edu
Date: 2009-05-12 at 2:00PM
Venue: MSC W301
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Abstract:
Title: Flips in Graphs
Seminar: Combinatorics
Speaker: Andrzej Dudek of Carnegie Mellon University
Contact: Vojtech Rodl, rodl@mathcs.emory.edu
Date: 2009-05-08 at 4:00PM
Venue: MSC W303
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Title: Patching Brauer groups III
Seminar: Algebra
Speaker: R. Preeti of IIT Bombay and Emory University
Contact: R. Parimala, parimala@mathcs.emory.edu
Date: 2009-05-05 at 1:00PM
Venue: MSC W303
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Abstract:
Title: Freudenthal triple systems via root system methods
Defense: PhD thesis
Speaker: Fred Helenius of Emory University
Contact: Skip Garibaldi, skip@mathcs.emory.edu
Date: 2009-05-04 at 3:00PM
Venue: MSC W301
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Abstract:
A Freudenthal triple system (FTS) is a vector space endowed with a quartic form and a bilinear form such that a triple product defined from these forms satisfies a specific identity. The original example is the 56-dimensional representation of E_7; here, the group stabilizing both forms is precisely E_7. M. Rost observed that an 8-dimensional vector space with quartic form occurring in a paper of M. Bhargava was, with a suitable bilinear form, a FTS; he asked what the stabilizer of the forms was in this case. We answer his question by showing that both his example and the 56-dimensional representation of E_7 are instances of a general construction that reveals a FTS within any Lie algebra of type B, D, E or F, with natural definitions for the quartic and bilinear forms.
Title: From boomerangs with strings to non-Euclidean tilings
Lecture Series: Evans/Hall
Speaker: Jeff Brock of Brown University
Contact: Steve Batterson, sb@mathcs.emory.edu
Date: 2009-04-28 at 4:00PM
Venue: Mathematics and Science Center: E208
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Abstract:
One day, a little French boy named Henri was playing in a field with his boomerang. He decided to try an experiment: ``what would happen," he thought, ``if I tied a very long string to my boomerang and then held on to one end. When the boomerang comes back," he wondered, ``will I be able to pull the string back to me while holding on to both ends?" ``Surely," he thought, ``as long as it doesn't get `caught' on something I can pull it back. But can it get caught on space itself?" Little Henri Poincaré probably never owned a boomerang, but one can imagine he may have had similar thoughts: his conjecture that any space where such a mathematical string never gets caught must be the three-dimensional sphere mystified mathematicians for nearly a hundred years. That is until a reclusive Russian named Grisha Perelman quietly posted three preprints on a public web server that settled Poincaré's question once and for all. Perelman's proof, a tour-de-force of three-dimensional geometry, presents as many new challenges as solutions. In this talk, I'll attempt to untangle elements of the history and conclusion of this elusive conjecture, and where we go from here. Along the way, we'll learn of non-Euclidean `Escher-esque' tilings, triangles whose interior angles don't add up to 180 degrees, how our universe is really just a pair of multi-handled coffee cups. The talk will be aimed at undergraduates but should be understandable to a lay audience.
Title: More Galois Theory
Graduate Student Seminar: Algebra
Speaker: Dr. Eric Brussel of Emory University
Contact: TBA
Date: 2009-04-22 at 4:00PM
Venue: MSC W201
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Abstract:
The study of objects defined as fixed points under a Galois action is a big part of the algebra program at Emory. We develop the basic setup, using nothing but 1st year graduate algebra.