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Saturday, February 24, 2018 - 09:30 ,
Location: Helen M. Aderhold Learning Center (ALC), Room 24 (60 Luckie St NW, Atlanta, GA 30303) ,
Wenjing Liao and others ,
GSU, Clemson,UGA, GT, Emory ,
Organizer: Sung Ha Kang

The Georgia Scientific Computing Symposium is a forum for professors,
postdocs, graduate students and other researchers in Georgia to meet in
an informal setting, to exchange ideas, and to highlight local
scientific computing research. The symposium has been held every year
since 2009 and is open to the entire research community. This year, the symposium will be held on Saturday, February 24, 2018, at Georgia State University. More information can be found at: https://math.gsu.edu/xye/public/gscs/gscs2018.html

Series: Other Talks

Degeneracy loci of morphisms between vector bundles have been used in a wide range of situations, including classical approaches to the Brill--Noether theory of special divisors on curves. I will describe recent developments in Schubert calculus, including K-theoretic formulas for degeneracy loci and their applications to K-classes of Brill--Noether loci. These recover the formulas of Eisenbud--Harris, Pirola, and Chan--López--Pflueger--Teixidor for Brill--Noether curves. This is joint work with Dave Anderson and Nicola Tarasca.

Series: Combinatorics Seminar

I will describe two new local limit theorems on the
Heisenberg group, and on an arbitrary connected, simply connected
nilpotent Lie group. The limit theorems admit general driving measures
and permit testing against test functions with an arbitrary
translation on the left and the right. The techniques introduced include
a rearrangement group action, the Gowers-Cauchy-Schwarz inequality, and
a Lindeberg replacement scheme which approximates the driving measure
with the corresponding heat kernel. These
results generalize earlier local limit theorems of Alexopoulos and
Breuillard, answering several open questions. The work on the
Heisenberg group is joint with Persi Diaconis.

Friday, February 23, 2018 - 15:00 ,
Location: Skiles 271 ,
Jiaqi Yang ,
GT Math ,
Organizer: Jiaqi Yang

We will present a rigorous proof of non-existence of homotopically non-trivial invariant circles for standard map:x_{n+1}=x_n+y_{n+1}; y_{n+1}=y_n+\frac{k}{2\pi}\sin(2\pi x_n).This a work by J. Mather in 1984.

Friday, February 23, 2018 - 13:55 ,
Location: Skiles 269 ,
Prof. Justin Kakeu ,
Morehouse University ,
Organizer: Sung Ha Kang

We use a stochastic dynamic programming approach to address the following question: Can a homogenous resource extraction model (one without extraction costs, without new discoveries, and without technical progress) generate non-increasing resource prices? The traditional answer to that question contends that prices should exhibit an increasing trend as the exhaustible resource is being depleted over time (The Hotelling rule). In contrast, we will show that injecting concerns for temporal resolution of uncertainty in a resource extraction problem can generate a non-increasing trend in the resource price. Indeed, the expected rate of change of the price can become negative if the premium for temporal resolution of uncertainty is negative and outweighs both the positive discount rate and the short-run risk premium. Numerical examples are provided for illustration.

Friday, February 23, 2018 - 10:00 ,
Location: Skiles 006 ,
Tim Duff ,
Georgia Tech ,
tduff3@gatech.edu ,
Organizer: Kisun Lee

TBA

Friday, February 23, 2018 - 10:00 ,
Location: Skiles 006 ,
Tim Duff ,
Georgia Tech ,
tduff3@gatech.edu ,
Organizer: Kisun Lee

Polyhedral homotopy methods solve a sparse, square polynomial system by deforming it into a collection of square "binomial start systems." Computing a complete set of start systems is generally a difficult combinatorial problem, despite the successes of several software packages. On the other hand, computing a single start system is a special case of the matroid intersection problem, which may be solved by a simple combinatorial algorithm. I will give an introduction to polyhedral homotopy and the matroid intersection algorithm, with a view towards possible heuristics that may be useful for polynomial system solving in practice.

Series: School of Mathematics Colloquium

A distinct covering system of congruences is a finite collection of arithmetic progressions $$a_i \bmod m_i, \qquad 1 < m_1 < m_2 < \cdots < m_k.$$Erdős asked whether the least modulus of a distinct covering system of congruences can be arbitrarily large. I will discuss my proof that minimum modulus is at most $10^{16}$, and recent joint work with Pace Nielsen, in which it is proven that every distinct covering system of congruences has a modulus divisible by either 2 or 3.

Wednesday, February 21, 2018 - 14:00 ,
Location: Skiles 006 ,
Kevin Kodrek ,
GaTech ,
Organizer: Anubhav Mukherjee

There are a number of ways to define the braid group. The traditional definition involves equivalence classes of braids, but it can also be defined in terms of mapping class groups, in terms of configuration spaces, or purely algebraically with an explicit presentation. My goal is to give an informal overview of this group and some of its subgroups, comparing and contrasting the various incarnations along the way.