## Seminars and Colloquia by Series

Series: Other Talks
Saturday, November 5, 2011 - 09:30 , Location: Petit Science Center, Room 124, Georgia State University , Featured Speaker Bela Bollobas , Cambridge University and University of Memphis , Organizer: Xingxing Yu

Emory University, the Georgia Institute of Technology and Georgia State University, with support from the National Security Agency and the National Science Foundation, are hosting a series of 9 mini-conferences from November 2010 - April 2013. The fourth in the series will be held at Georgia State University on November 5-6, 2011. This mini-conference's featured speaker is Dr. Bela Bollobas, who will give two one-hour lectures. Additionally, there will be five one-hour talks and seven half-hour talks given by other invited speakers. See all titles, abstracts, and schedule.
Series: Other Talks
Wednesday, November 2, 2011 - 17:15 , Location: Skiles 005 , David Brown , Department of Mathematics and Computer Science, Emory University , Organizer:
Knowledge of the distribution of class groups is elusive -- it is not even known if there are infinitely many number fields with trivial class group. Cohen and Lenstra noticed a strange pattern -- experimentally, the group \mathbb{Z}/(9) appears more often than \mathbb{Z{/(3) x \mathbb{Z}/(3) as the 3-part of the class group of a real quadratic field \Q(\sqrt{d}) - and refined this observation into concise conjectures on the manner in which class groups behave randomly. Their heuristic says roughly that p-parts of class groups behave like random finite abelian p-groups, rather than like random numbers; in particular, when counting one should weight by the size of the automorphism group, which explains why \mathbb{Z}/(3) x \mathbb{Z}/(3) appears much less often than \mathbb{Z}/(9) (in addition to many other experimental observations). While proof of the Cohen-Lenstra conjectures remains inaccessible, the function field analogue -- e.g., distribution of class groups of quadratic extensions of \mathbb{F}_p(t) -- is more tractable. Friedman and Washington modeled the \el$-power part (with \ell \neq p) of such class groups as random matrices and derived heuristics which agree with experiment. Later, Achter refined these heuristics, and many cases have been proved (Achter, Ellenberg and Venkatesh). When$\ell = p$, the$\ell\$-power torsion of abelian varieties, and thus the random matrix model, goes haywire. I will explain the correct linear algebraic model -- Dieudone\'e modules. Our main result is an analogue of the Cohen-Lenstra/Friedman-Washington heuristics -- a theorem about the distributions of class numbers of Dieudone\'e modules (and other invariants particular to \ell = p). Finally, I'll present experimental evidence which mostly agrees with our heuristics and explain the connection with rational points on varieties.
Series: Other Talks
Wednesday, November 2, 2011 - 16:00 , Location: Skiles 005 , Jared Weinstein , Institute for Advanced Study and Boston University , Organizer:
This is joint work with Mitya Boyarchenko. We construct a special hypersurface X over a finite field, which has the property of "maximality", meaning that it has the maximum number of rational points relative to its topology. Our variety is derived from a certain unipotent algebraic group, in an analogous manner as Deligne-Lusztig varieties are derived from reductive algebraic groups. As a consequence, the cohomology of X can be shown to realize a piece of the local Langlands correspondence for certain wild Weil parameters of low conductor.
Series: Other Talks
Monday, October 31, 2011 - 11:00 , Location: Skiles 114 , Will Perkins , Georgia Tech , Organizer: Christine Heitsch
A discussion of the Moulton et all (2000) paper "Metrics on RNA Secondary Structures."
Series: Other Talks
Wednesday, October 26, 2011 - 15:00 , Location: IBB 1128 , Christopher Jones , University of North Carolina at Chapel Hill, Department of Mathematics , Organizer:

Joint colloquium between the School of Physics & the School of Earth and Atmospheric Sciences
hosted by Predrag Cvitanovi.
To schedule a meeting with the speaker</a>.

Computational models of the Earth system lie at the heart of modern climate science. Concerns about their predictions have been illegitimately used to undercut the case that the climate is changing and this has put dynamical systems in an awkward position. I will discuss ways that we, as a community, can contribute by highlighting some of the major outstanding questions that drive climate science, and I will outline their mathematical dimensions. I will put a particular focus on the issue of simultaneously handling the information coming from data and models. I will argue that this balancing act will impact the way in which we formulate problems in dynamical systems.
Series: Other Talks
Monday, October 24, 2011 - 11:00 , Location: Skiles 114 , Todd Shayler , Georgia Tech , Organizer: Christine Heitsch
A discussion of the Allali and Sagot (2005) paper "A New Distance for High Level RNA Secondary Structure Comparison."
Series: Other Talks
Monday, October 10, 2011 - 11:00 , Location: Skiles 114 , Emily Rogers , Georgia Tech , Organizer: Christine Heitsch
Continued discussion of the Ding, Chan, and Lawrence paper (2005) "RNA secondary structure prediction by centroids in a Boltzmann weighted ensemble."
Series: Other Talks
Monday, October 3, 2011 - 11:00 , Location: Skiles 114 , Emily Rogers , Georgia Tech , Organizer: Christine Heitsch
A discussion of the Ding, Chan, and Lawrence paper (2005) "RNA secondary structure prediction by centroids in a Boltzmann weighted ensemble."
Series: Other Talks
Monday, September 26, 2011 - 11:00 , Location: Skiles 114 , Greg Blekherman , Georgia Tech , Organizer: Christine Heitsch
A discussion of the Ding & Lawrence (2003) paper "A statistical sampling algorithm for RNA secondary structure prediction."
Series: Other Talks
Monday, September 19, 2011 - 11:00 , Location: Skiles 114 , Rohit Banga, Prashant Gaurav, and Manoj Soni , Georgia Tech , Organizer: Christine Heitsch
A discussion of the  Chan & Ding (2008) paper "Boltzmann ensemble features of RNA secondary structures: a comparative analysis of biological RNA sequences and random shuffles."