Topologically all Cantor sets are the same. Nevertheless, thee are many ways to assign a quantitative characteristic to Cantor sets, and these notions play important role in applications to dynamical systems, number theory, spectral theory, and other areas of mathematics. We will describe some of the characteristics (e.g. fractal dimentions, thickness) of Cantor sets and the ways one can calculate and use them.
The structure of Anosov-Katok example (in fact, this is a series of examples that can be constructed using similar techniques) will be presented. This is a way to build a smooth realization for several classes of measure preserving transformations.
We will review the recent (and not so recent) results on dynamics of piecewise isometries (especially piecewise translations), both in one and in higher dimensional case. Some interesting results (by Suzuki, Goetz, Zhuravlev, Boshernitzan, Bruin, Troubetzkoy, Buzzi) are known, but most of natural questions are still open. The main goal of the talk is to expose these open questions to potential researchers.
We study discrete Schr ̈odinger operators with trigonomet-
ric potentials. In particular, we are interested in the connection be-
tween the absolutely continuous spectrum in the almost periodic case
and the spectra in the periodic case. We prove a weak form of a precise
conjecture relating the two.
We also bound the measure of the spectrum in the periodic case in
terms of the Lyapunov exponent in the almost periodic case.
In the proofs, we use a partial generalization of Chambers formula.
As an additional application of this generalization, we provide a new
proof of Hermans lower bound for the Lyapunov exponent.
We discuss the continuous time percolation model in an ergodically defined
environment. Under minimal assumptions on the ergodic system, we show the
existence of sets of sampling functions with percolation or extinction
showing that the latter are dense open. We also discuss the related
spatially inhomogeneous continuous time random cluster model and the
topological properties of sets of sampling functions corresponding to
percolation and decay.
In scientific and engineering computing, one major computational bottleneck is the solution of large scale linear algebraic systems resulted from the discretization of various partial differential equations (PDEs). These systems are still often solved by traditional methods such as Gaussian elimination in many practical applications. Mathematically optimal methods, such as multigrid methods, have been developed for decades but they are still not much used in practice. In this talk, I will report some recent advances in the development of optimal multilevel iterative methods that can be applied to various practical problems in a user-friendly fashion. Starting from some basic ideas of designing efficient iterative methods such as multigrid and domain decomposition methods, I will give a brief description of a general framework known as the Fast Auxiliary Space Preconditioning (FASP) Methods and report some applications in various problems including Newtonian and non-Newtonian models, Maxwell equations, Magnetohydrodymics and battery and reservoir (porous media) simulations.
Magnetic resonance images typically contain signals from multiple chemical species such as water and fat. The diagnostic information in the image can be improved by separating the components of the signal coming from individual chemical species. The model that describes the signal generation includes non-linear parameters which arise from imperfections in the magnetic field and signal decay. The Cramer-Rao Bound is the minimum variance of an unbiased estimator of a parameter. In this work, we use the Cramer-Rao Bound to optimize the data acquisition for the non-linear inverse problem of estimating the magnetic field inhomogeneities and signal decay.