[Vortraege] Vortragsankuendigungen der kommenden Woche (KW 23)

Fri May 30 12:55:10 CEST 2008

Sehr geehrte Fakultätsmitglieder,

anbei die Vortragsankündigungen für kommende Woche:

Mittwoch, 4. Juni 2008, C 209

Außerordentliches Mathematisches Kolloquium

Einladung zu einem Vortrag im Rahmen der Habilitation von

Dr. Massimo Fornasier (Johann Radon Institute for Computational and 
Applied Mathematics, Linz)

(Kommissionsvorsitzender Univ.-Prof. Dr. Christian Schmeiser)

Beginn: 14:30 Uhr

"Compressive Algorithms. Adaptive Solutions of PDEs and Variational Problem"

Abstract: Solutions of certain PDEs and variational problems may be 
characterized bya few significant degrees of freedom, and one may want 
to take advantage of this feature in order to design efficient numerical 
solutions. Examples of such situations are ubiquitous: adaptive solution 
of PDEs, singular PDEs for image processing, crack modelling and 
free-discontinuity problems, viscosity solutions of Hamilton-Jacobi 
equations, digital signal coding/decoding, and compressed sensing. We 
studied compressive algorithms which are based on thresholded gradient 
iterations in several contexts. In the first part of the talk we address 
the issue of embedding compressibility in numerical simulation, and in 
particular the use of adaptive strategies for the solution of elliptic 
partial differential equations discretized by means of redundant frames. 
We discuss the construction of wavelet frames on bounded domains and the 
optimal performances of adaptive solvers based on thresholded 
iterations. In the second part of the talk we review the role of 
variational principles, in particular L1 minimization, as a method for 
sparsifying solutions in several contexts. Then we address particular 
applications and numerical methods. We present the analysis of 
algorithms for performing efficiently L1-minimization, based on 
projected gradient methods and thresholded 
subspace-correction/domain-decomposition methods. We illustrate the 
theoretical results also by means of numerical experiments in image 
processing, geophysics, and magnetoencephalography. We conclude with the 
presentation of recent results which clarify the superlinear convergence 
of an algorithm for L1-minimization based on an iteratively re-weighted 
least-square method. An analogous algorithm is then illustrated for the 
efficient solution of a system of singular PDEs for image recolorization 
in a relevant real-life problem of art restoration.

Mittwoch, 4. Juni 2008, C 209

Außerordentliches Mathematisches Kolloquium

Einladung zu einem Vortrag im Rahmen der Habilitation von

Dr. Holger Rauhut (Hausdorff Center for Mathematics, Universität Bonn)

(Kommissionsvorsitzender o. Univ.-Prof. Dr. Arnold Neumaier)

Beginn: 16:15 Uhr

"Sparse Recovery"

In recent years sparsity has become a key concept in applied 
 mathematics, in particular, signal processing. The basic observation is 
that many types of signals can be represented well by a small number of 
non-vanishing coefficients with respect to a suitable basis, i.e., by a 
sparse representation. This is for instance the reason why compression 
techniques such as JPEG or MPEG work so well.

In 2004, it was observed by Candès, Romberg and Tao, and independently, 
by David Donoho, that sparsity can also be exploited for measuring or 
capturing signals efficiently, that is, by using only a small number of 
linear non-adaptive measurements. This principle is called compressed 
sensing, compressive sampling, or sparse recovery. The talk gives an 
overview on sparse recovery with an emphasis on results obtained by the 
speaker. In particular, we discuss recovery of sparse trigonometric 
polynomials from a small number of random samples, as well as recovery 
of sparse time-frequency representations.

Dazwischen Kaffeejause im Common Room

2. Juni 2008 bis 6. Juni 2008, ESI – Erwin Schrödinger Institut, 
Boltzmann Lecture Hall, Boltzmanngasse 9, 1090 Wien

ESI – Programm

„Hyperbolic Dynamical Systems – Focus Week on Nonequilibrium Processes“

Attachment anbei: Programm

Dienstag, 3. Juni 2008, ESI Schrödinger Lecture Hall, Boltzmanng. 9

Arbeitsgemeinschaft Diskrete Mathematik am Erwin Schrödinger Institut

14:00 Uhr: George Andrews (Pennsylvania State University)

„Partitions, Durfee Symbols and the Atkin-Garvan Moments of Ranks“

Abstract: In 1944, Freeman Dyson defined the rank of a partition with 
the object of providing a combinatorial interpretation of the Ramanujan 
conguences for the partition function, p(n).  Dyson's discoveries and 
conjectures have led to an extensive field of research with exciting 
discoveries by Atkin, Garvan, Swinnerton-Dyer, Ono, Bringmann and 
Mahlburg and others.  In this talk, we consider moments that Atkin and 
Garvan associated with the ranks defined by Dyson.  We shall reveal the 
objects they enumerate and shall discuss implications and possibilities.

16:00 Uhr: Yao-zhong Zhang (University of Queensland)

„Drinfeld twists, symmetric Bethe vectors and correlation functions  in 
SUSY integrable models“

 Dienstag, 3. Juni 2008, HS D1.03, UZA 4

Arbeitsgemeinschaft Biomathematik

15:00 Uhr: Ellen Baake (Bielefeld)

„Ancestral processes with selection: branching and Moran models. I“

Dienstag, 3. Juni 2008, Wolfgang Pauli Institut, WPI Seminar Room C 714, 
Nordbergstraße 15, 1090 Wien

WK Seminar

14:00 Uhr: Corrias Lucilla (Université d’Evry Val d’Essonne)

/„Mathematical Properties of the Keller Segel System: Global Existence 
and Blow-Up“/
/ /
Abstract: The biological process of chemotaxis, i.e. the direct movement 
of a biological population towards a chemical signal, can be modeled by 
the so-called Keller-Segel system describing the evolution of the 
population density and of the chemical con- centration. In this talk we 
will present this model and its main mathematical properties, i.e. a 
priori estimates, global existence and blow-up in dimension $dge2$.
/ /

Donnerstag, 5 Juni 2008, Wolfgang Pauli Institut, Seminar Room 101C, 4 
Fl., TU Wien, Wiedner Hauptstraße 8, 1040 Wien

WK Student Seminar

16:00 Uhr: Ziehaus Christina

/„The Martingale Approach for Optimal Consumption“/

Abstract: To solve the optimal consumption and investment problem, there 
exist two different methods. This talk will concentrate on the 
martingale approach ("the dual approach"). The market setting is a 
geometric Ornstein-Uhlenbeck market. Estimates for long-term behavior 
will be presented.

16:00 Uhr: Kristöfel Peter

Donnerstag, 5. Juni 2008, D 107

Geometry Seminar

15:30 Uhr – 17:00 Uhr: ao. Univ.-Prof. Dr. Peter Michor

„Geometry and Curvature of Shape Spaces“

Abstract: Here Shape space consists of either: sets of ordered points on 
R^n (landmark space), submanifolds of R^n, even certain currents in R^n. 
The group of diffeomorphisms with compact support acts transitively on 
shape space, and we induce Riemannian metrics on shape space induced 
from right invariant Sobolev metrics in the diffeomorphism groups. This 
offers interesting analytical difficulties. The resulting geodesic 
equations are well posed. Curvature can be computed in two ways: 
directly, or via O'Neill's formula from Arnold's curvature on the 
diffeomorphism group.

Montag, 2. Juni 2008, RICAM in Linz

SE Algebraic Geometry

11:00 Uhr - 17:00 Uhr

„Cohomology Theory; motivation, basic definitions and properties, 
universal coefficient theorem“

Dienstag, 3. Juni 2008, 2A180 UZA II

SE Commutative Algebra

13:15 – 15:00

„Integrality and Dimension. Integral closure of ideals“

Freitag, 6. Juni 2008, Kleiner Seminarraum 104 (Vienna University of 
Technology, Wiedner Hauptstrasse 8-10, 1040 Wien, Freihaus, fifth floor, 
green zone).

Algebra Seminar

12:15 Uhr: Libor Polak

„Algebraic Language Theory“

Noch eine allgemeine Information:
Es wird (von Prof. Feichtinger) empfohlen, den Austrian Talk-Server f. 
Mathematik als Bookmark auf der privaten Homepage einzurichten, und in 
der laufenden Probephase eventuelle Probleme oder Maengel an Herrn Dr. 
Mayer (man.mayer at aon.at <mailto:man.mayer at aon.at>) zu melden. 
Mittelfristig sollte der Talk-Server die Zentrale Informationsquelle 
sind, wo alle math. Events Oesterreichs laufend aktuell und 
uebersichtlich aufgelistet zu finden sind.

Link: MathTalksAustria - Österreichischer Vortragsserver:
http://ats.mat.univie.ac.at:3000/home/this_week

Mit herzlichen Grüßen
und ein schönes Wochenende!
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