Events for 11/28/2018 from all calendars

Noncommutative Geometry Seminar

Time: 2:00PM - 3:00PM

Location: BLOC 628

Speaker: Jinmin Wang, Texas A&M University

Title: Higher rho invariant and pairings with higher cyclic cocyles

Abstract: In this talk, I will introduce a pairing map between K-theory of obstruction algebra and higher cyclic cocyles for the group algebras of hyperbolic groups. The main focus of this pairing is to establish a connection between two different approaches to the index theory of manifolds with boundaries. This is joint work with Xiaoman Chen, Zhizhang Xie and Guoliang Yu.

Numerical Analysis Seminar

Time: 3:00PM - 4:00PM

Location: BLOC 628

Speaker: Per-Olof Persson, UC Berkely

Title: High-Order Discontinuous Galerkin Methods for Fluid and Solid Mechanics

Abstract: It is widely believed that high-order accurate numerical methods, for example discontinuous Galerkin (DG) methods, will eventually replace the traditional low-order methods in the solution of many problems, including fluid flow, solid dynamics, and wave propagation. The talk will give an overview of this field, including the theoretical background of the numerical schemes, the efficient implementation of the methods, and examples of real-world applications. Topics include high-order compact and sparse numerical schemes, high-quality unstructured curved mesh generation, scalable preconditioners for parallel iterative solvers, fully discrete adjoint methods for PDE-constrained optimization, and implicit-explicit schemes for the partitioning of coupled fluid-structure interaction problems. The methods will be demonstrated on some important practical problems, including the inverse design of energetically optimal flapping wings and large eddy simulation (LES) of wind turbines.

Groups and Dynamics Seminar

Time: 3:00PM - 4:00PM

Location: BLOC 220

Speaker: Roman Kogan

Title: Graphs of Action and the Automatic Logarithm

Abstract: We introduce a new construction, called the Automatic Logarithm, motivated by the study of graphs of action of the group generated by two Mealy automata, A and B, on the levels of the infinite rooted binary tree T, in the case where A is level-transitive and of bounded activity. The automatic logarithm L_{A,B} computes the length of chords in these graphs. As a function form the boundary of the tree dT to dyadics Z_2, its values are given by a Moore machine whose output is interpreted as a dyadic integer.

Colloquium - Alex Blumenthal

Time: 4:00PM - 5:00PM

Location: BLOC 220

Speaker: Alex Blumenthal, University of Maryland, College Park

Description: Title: Chaotic regimes for random dynamical systems
Abstract: It is anticipated that chaotic regimes (e.g., strange attractors) arise in a wide variety of dynamical systems, including those arising from the study of ensembles of gas particles and fluid mechanics. However, in most cases the problem of rigorously verifying asymptotic chaotic regimes is notoriously difficult. For volume-preserving systems (e.g., incompressible fluid flow or Hamiltonian systems), these issues are exemplified by coexistence phenomena: even in quite simple models which should be chaotic, e.g. the Chirikov standard map, completely opposite dynamical regimes (elliptic islands vs. hyperbolic sets) can be tangled together in phase space in a convoluted way. Recent developments have indicated, however, that verifying chaos is tractable for systems subjected to a small amount of noise— from the perspective of modeling, this is not so unnatural, as the real world is inherently noisy. In this talk, I will discuss two recent results: (1) a large positive Lyapunov exponent for (extremely small) random perturbations of the Chirikov standard map, and (2) a positive Lyapunov exponent for the Lagrangian flow corresponding to various incompressible stochastic fluids models, including stochastic 2D Navier-Stokes and 3D hyperviscous Navier-Stokes on the periodic box. The work in this talk is joint with Jacob Bedrossian, Samuel Punshon-Smith, Jinxin Xue and Lai-Sang Young.

First Year Graduate Student Seminar

Time: 5:30PM - 6:30PM

Location: BLOC 628

Speaker: Peter Howard

Title: Preparing for Spring 2019

AMUSE

Time: 6:00PM - 7:00PM

Location: BLOC 220

Speaker: Dr. Alexey Belyanin, Department of Physics and Astronomy, Texas A&M University

Title: Lasers meet nanotechnology

Abstract: Modern nanotechnology enables precise quantum “engineering” of quantum states of individual electrons in crystals and their coupling to light. Advances in nanotechnology have led to the appearance of microscopic lasers with functionalities that would be considered science fiction just a few years ago. I will discuss how fundamental laws of quantum mechanics and electromagnetism enable several recent additions to a zoo of lasers: lasers for the Internet, lasers that can “see through the wall”, quantum cascade lasers, laser frequency combs, laser radio, and lasers that can detect one molecule hidden within a trillion other molecules. This is like finding a needle in a haystack the size of Kyle Field.