PII Networking Industrial Workshops - Medical Imagery

02/08/2016 - 00:00
02/08/2016 - 23:59
Speaker: 
Organizer: Stéphane Rouillon (Université de Montréal)
Location: 
Room 6254 of Pavillon André-Aisenstadt on the Université de Montréal campus.
Last edited by on Thu, 02/04/2016 - 14:29

Epi-convergent Smoothing with Applications to Convex Composite Functions

02/22/2016 - 16:00
Speaker: 
Tim Hoheisel, University of Wrzburg
Location: 
Burnside Hall 1205
Abstract: 

Smoothing methods have become part of the standard tool set for the study and solution of nondifferentiable and constrained optimization problems as well as a range of other variational and equilibrium problems. In this note we synthesize and extend recent results due to Beck and Teboulle on infimal convolution smoothing for convex functions with those of X.Chen on gradient consistency for nonconvex functions.

We use epi-convergence techniques to define a notion of epi-smoothing that allows us to tap into the rich variational structure of the subdifferential calculus for nonsmooth, nonconvex, and nonfinite-valued functions. As an illustration of the versatility and range of epi-smoothing techniques, the results are applied to the general constrained optimization for which nonlinear programming is a special case.

Last edited by on Mon, 02/01/2016 - 10:21

TBA

02/04/2016 - 16:00
02/04/2016 - 17:30
Speaker: 
Janosch Ortmann
Location: 
Concordia University, Math Help Center, room 912.00 / Library Building, 1400 de Maisonneuve Blvd. West, Montréal
Last edited by on Fri, 01/29/2016 - 16:20

Managing design-time uncertainty in software engineering

02/04/2016 - 15:30
02/04/2016 - 16:30
Speaker: 
Michalis Famelis, (UBC)
Location: 
Colloquium DIRO, Université de Montréal, Pavillon André-Aisenstadt, 2920 ch. de la Tour, salle 3195
Abstract: 

Every software system is the accumulated result of a myriad of design decisions. But what happens when developers are uncertain about how to make these decisions? The best developer teams are those that are experts at keeping possible options open, juggling multiple design alternatives, and avoiding premature commitments. However, existing tools, languages and methodologies rarely, if ever, take design-time uncertainty into account. I will present a formal but practical framework that supports deferring design decisions while uncertainty persists, allowing development and analysis to continue. This requires drawing from diverse areas of software engineering to create novel abstractions, notations and automation approaches to seamlessly "lift" existing operations to correctly and efficiently handle sets of possible solutions to open design decisions.

Last edited by on Fri, 01/29/2016 - 16:18

Que peut-on dire sur un système dynamique hamiltonien qu'on ne connaît pas ?

02/03/2016 - 12:30
02/03/2016 - 13:30
Speaker: 
Jordan Payette, Université de Montréal
Location: 
Université de Montréal, Pavillon Claire-McNicoll, salle Z-345
Abstract: 

Les systèmes dynamiques hamiltoniens modélisent la vaste majorité des systèmes « fondamentaux » de la physique classique et, de manière plus méconnue, de la physique quantique. Ce faisant, leur étude mathématique est centrale à notre compréhension du monde. Malheureusement, il est en général très difficile, voire impossible, d'exprimer précisément l'évolution temporelle d'un système hamiltonien. Qui plus est, faute d'information sur un système physique réel, on ne sait pas quel système hamiltonien le modélise « véritablement ».

Last edited by on Fri, 01/29/2016 - 16:16

Three-dimensional superintegrable systems in a static electromagnetic field

02/02/2016 - 15:30
02/02/2016 - 16:30
Speaker: 
Libor Snobl (Czech Technical University, Prague)
Location: 
CRM, UdeM, Pavillon André-Aisenstadt, 2920, ch. de la Tour, salle 4336
Abstract: 

We consider a charged particle moving in a static electromagnetic field described by the vector potential $vec{A}(vec{x})$ and the electrostatic potential $V(vec{x}).$ We study the conditions on the structure of the integrals of motion of the first and second order in momenta, in particular how they are influenced by the gauge invariance of the problem. Next, we concentrate on the three possibilities for integrability arising from the first order integrals corresponding to three nonequivalent subalgebras of the Euclidean algebra, namely $({P}_{1},{P}_{2}),$ $({L}_{3},{P}_{3})$ and $({L}_{1},{L}_{2},{L}_{3}).$ For these cases we look for additional independent integrals of first or second order in the momenta. These would make the system superintegrable (minimally or maximally). We study their quantum spectra and classical equations of motion. In some cases nonpolynomial integrals of motion occur and ensure maximal superintegrability.

Last edited by on Fri, 01/29/2016 - 16:07

Interactions of forward-and backward-time isochrons

02/15/2016 - 15:00
02/15/2016 - 16:00
Speaker: 
Peter Langford (McGill University)
Location: 
McGill University, 805 Sherbrooke St. West, Burnside Hall, BURN 920, 9TH FLOOR
Abstract: 

In the 1970s Winfree introduced the concept of an isochron as the set of all points in the basin of an attracting periodic orbit that converge to the periodic orbit in forward time with the same asymptotic phase. It has been observed that in slow-fast systems, such as the FitzHugh-Nagumo model, the isochrons of such systems can have complicated geometric features; in particular, regions with high curvature that are related to sensitivity in the system. In order to understand where these features come from, we introduce backward-time isochrons that exist in the basin of a repelling periodic orbit, and we consider their interactions with the forward-time isochrons. We show that a cubic tangency between the two sets of isochrons is responsible for creating high curvature features. This study makes use of a boundary value problem formulation to compute isochrons accurately as parametrised curves.

Last edited by on Fri, 01/29/2016 - 16:04

Harry Potter's Cloak via Transformation Optics

03/18/2016 - 16:00
03/18/2016 - 17:00
Speaker: 
Gunther Uhlmann, (University of Washington)
Location: 
CRM, UdeM, Pav. André-Aisenstadt, 2920, ch. de la Tour, salle 6214
Abstract: 

Resume/Abstract :

Can we make objects invisible? This has been a subject of human fascination for millennia in Greek mythology, movies, science fiction, etc., including the legend of Perseus versus Medusa and the more recent Star Trek and Harry Potter. In the last decade or so, there have been several scientific proposals to achieve invisibility. We will introduce some of these in a non-technical fashion, concentrating on the so-called "transformation optics" that has received the most attention in the scientific literature.

 

Last edited by on Fri, 01/29/2016 - 15:36

Ricci curvature and geometric analysis on graphs

02/23/2016 - 15:30
02/23/2016 - 16:30
Speaker: 
Yong Lin, Renmin (University of China)
Location: 
CRM, UdeM, Pavillon André-Aisenstadt, 2920, ch. de la Tour, salle 4336
Abstract: 

Abstract: Ricci curvature lower bound play very important rule for geometric analysis on Riemannian manifold. So it is very interesting to introduce similar concept on discrete setting especially on graphs. We will talk about the Ricci curvature lower bound on graphs where the original idea comes from the Bochner formula on Riemannian geometry. Given the Ricci curvature lower bound on graphs, we will imply some classic results from Riemannian manifold for eigenvalue estimate, gradient estimate, Harnack inequality and heat kernel estimate and so on.

Last edited by on Fri, 01/29/2016 - 15:31

Solyanik Estimates in Harmonic Analysis

02/19/2016 - 13:30
02/19/2016 - 14:30
Speaker: 
Paul Hagelstein (Baylor)
Location: 
McGill University, 805 Shrebrooke St. West, Burnside Hall, Burn 920, 9th floor
Abstract: 

Let $mathcal{B}$ be a collection of open sets in $mathbb{R}^n$. Associated to $mathcal{B}$ is the geometric maximal operator $M_{mathcal{B}}$ defined by $$M_{mathcal{B}}f(x) = sup_{x in R in mathcal{B}}int_R|f|;.$$ For $0 < alpha < 1$, the associated emph{Tauberian constant} $C_{mathcal{B}}(alpha)$ is given by $$C_{mathcal{B}}(alpha) = sup_{E subset mathbb{R}^n : 0 < |E| < infty} rac{1}{|E|}|{x in mathbb{R}^n : M_{mathcal{B}}chi_E(x) > alpha}|;.$$ A maximal operator $M_mathcal{B}$ such that $lim_{alpha ightarrow 1^-}C_{mathcal{B}}(alpha) = 1$ is said to satisfy a emph{Solyanik estimate}. In this talk we will prove that the uncentered Hardy-Littlewood maximal operator satisfies a Solyanik estimate. Moreover, we will indicate applications of Solyanik estimates to smoothness properties of Tauberian constants and to weighted norm inequalities. We will also discuss several fascinating open problems regarding Solyanik estimates.

This research is joint with Ioannis Parissis.

Last edited by on Fri, 02/12/2016 - 14:55