Seminars and Colloquia by Series

Friday, November 10, 2017 - 13:55 , Location: Skiles 006 , John Etnyre , Georgia Tech , Organizer: John Etnyre
  In this series of talks I will introduce branched coverings of manifolds and sketch proofs of most the known results in low dimensions (such as every 3 manifold is a 3-fold branched cover over a knot in the 3-sphere and the existence of universal knots). This week we continue discussing branched covers of 3-manifolds and prove universal links exist. 
Thursday, November 9, 2017 - 15:05 , Location: Skiles 006 , Elliot Paquette , The Ohio State University , paquette.30@osu.edu , Organizer: Lutz Warnke
We study an online algorithm for making a well—equidistributed random set of points in an interval, in the spirit of "power of choice" methods. Suppose finitely many distinct points are placed on an interval in any arbitrary configuration. This configuration of points subdivides the circle into a finite number of intervals. At each time step, two points are sampled uniformly from the interval. Each of these points lands within some pair of intervals formed by the previous configuration. Add the point that falls in the larger interval to the existing configuration of points, discard the other, and then repeat this process. We then study this point configuration in the sense of its largest interval, and discuss other "power of choice" type modifications. Joint work with Pascal Maillard.
Thursday, November 9, 2017 - 15:00 , Location: Skiles 006 , Elliot Paquette , The Ohio State University , paquette.30@osu.edu , Organizer: Lutz Warnke
We study an online algorithm for making a well—equidistributed random set of points in an interval, in the spirit of "power of choice" methods. Suppose finitely many distinct points are placed on an interval in any arbitrary configuration. This configuration of points subdivides the circle into a finite number of intervals. At each time step, two points are sampled uniformly from the interval. Each of these points lands within some pair of intervals formed by the previous configuration. Add the point that falls in the larger interval to the existing configuration of points, discard the other, and then repeat this process. We then study this point configuration in the sense of its largest interval, and discuss other "power of choice" type modifications. Joint work with Pascal Maillard.
Thursday, November 9, 2017 - 13:30 , Location: Skiles 005 , Shijie Xie , Math, GT , Organizer: Robin Thomas
Let G be a graph containing 5 different vertices a0, a1, a2, b1 and b2. We say that (G, a0, a1, a2, b1, b2) is feasible if G contains disjoint connected subgraphs G1, G2, such that {a0, a1, a2}⊆V(G1) and {b1, b2}⊆V(G2). In this talk, we will prove the existence of 5-edge configurations in (G, a0, a1, a2, b1, b2). Joint work with Changong Li, Robin Thomas, and Xingxing Yu.
Wednesday, November 8, 2017 - 13:55 , Location: Skiles 006 , Agniva Roy , Georgia Tech , Organizer: Jennifer Hom
The Lickorish Wallace Theorem states that any closed 3-manifold is the result of a +/- 1-surgery on a link in S^3. I shall discuss the relevant definitions, and present the proof as outlined in Rolfsen's text 'Knots and Links' and Lickorish's 'Introduction to Knot Theory'. 
Wednesday, November 8, 2017 - 13:55 , Location: Skiles 005 , Francisco Villarroya , UGA , paco.villarroya@uga.edu , Organizer: Michael Lacey
In this talk I will introduce a Tb Theorem that characterizes all Calderón-Zygmund operators that extend compactly on L^p(R^n) by means of testing functions as general as possible. In the classical theory for boundedness, the testing functions satisfy a non-degeneracy property called accretivity, which essentially implies the existence of a positive lower bound for the absolute value of the averages of the testing functions over all dyadic cubes. However, in the setting of compact operators, due to their better properties, the hypothesis of accretivity can be relaxed to a large extend. As a by-product, the results also describe those Calderón-Zygmund operators whose boundedness can be checked with non-accretive testing functions.
Wednesday, November 8, 2017 - 12:10 , Location: Skiles 006 , Michael Worthington , GA Tech , Organizer: Timothy Duff
Series: PDE Seminar
Tuesday, November 7, 2017 - 15:00 , Location: Skiles 006 , Chun Liu , Illinois Institute of Technology , cliu124@iit.edu , Organizer: Yao Yao
Almost all biological activities involve transport and distribution of ions and charged particles. The complicated coupling and competition between different ionic solutions in various biological environments give the intricate specificity and selectivity in these systems. In this talk, I will introduce several extended general diffusion systems motivated by the study of ion channels and ionic solutions in biological cells. In particular, I will focus on the interactions between different species, the boundary effects and in many cases, the thermal effects.
Tuesday, November 7, 2017 - 13:00 , Location: Skiles 006 , Günter Stolz , University of Alabama, Birmingham , stolz@uab.edu , Organizer: Michael Loss
Tuesday, November 7, 2017 - 10:00 , Location: Skiles 006 , Yulia Karpeshina , University of Alabama, Birmingham , karpeshi@uab.edu , Organizer: Michael Loss
  Existence of ballistic transport for Schr ̈odinger operator with a quasi- periodic potential in dimension two is discussed. Considerations are based on the following properties of the operator: the spectrum of the operator contains a semiaxis of absolutely continuous spectrum and there are generalized eigenfunctions being close to plane waves ei⟨⃗k,⃗x⟩ (as |⃗k| → ∞) at every point of this semiaxis. The isoenergetic curves in the space of momenta ⃗k corresponding to these eigenfunctions have a form of slightly distorted circles with holes (Cantor type structure). 

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