# Talks

2024 | 2023 | 2022 | 2021 | 2019 | 2018 | 2017 | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005

## 2024

A block Householder based QR decomposition of hierarchical matrices
Workshop on Advanced numerical methods for non-local problems, Istanbul, Turkey, Jan. 9-11, 2024

## 2023

Relaxation in low-rank updates of Schur complement preconditioners in fluid flow problems
10th International Congress on Industrial and Applied Mathematics (ICIAM), Tokyo, August 20-25, 2023

A block Householder based QR decomposition using hierarchical matrices
Workshop on Computational Science and Engineering, Groß Schwansee, 20.-22.3.2023

## 2022

A block Householder based QR decomposition of hierarchical matrices
GAMM ANLA Conference 2022, Prag, September 22-23, 2022

A block Householder based QR decomposition of hierarchical matrices
GAMM Annual Conference 2022, invited section keynote presentation in section S17: Applied and numerical linear algebra, RWTH Aachen, August 15-19, 2022

Stages of Academia, presentation and discussion in the series Stages of Academia
invitation by UHH SIAM student chapter/GAMM Nachwuchsgruppe, August 9, 2022

A block Householder based QR decomposition of hierarchical matrices
SIAM Annual Meeting 2022, Pittsburgh (hybrid), July 11-15, 2022

## 2021

Potential (&) pitfalls in RBF-FD discretization of PDEs
Workshop on "Hierarchical Numerical Methods for PDEs", Max-Planck-Institut für Mathematik in den Naturwissenschaften, Leipzig, September 28-29, 2021

Mathematician meets physicist: High performance simulations of next generation light sources
Workshop on "Modeling, Simulation and Optimization of Fluid Dynamic Applications" (GrK 2583), Groß Schwansee, September 6-9, 2021

Der ewige Flaschenhals der Computersimulation - Moderne Verfahren für lineare Gleichungssysteme
Kolloquiumsvortrag im Rahmen des Allgemeinen Vorlesungswesens der Universität Hamburg, 25 May 2021

## 2019

Numerical techniques for particle aggregation
Kolloquiumsvortrag an der Tennessee Technological University, Cookeville, TN, USA, 3 October, 2019

Preconditioners for RBF-FD discretized fluid-flow problems
GAMM Workshop on Applied and Numerical Linear Algebra, Chemnitz, 26-27 September,
2019

Preconditioners for RBF-FD discretized fluid-flow problems
CIRM Workshop on “Parallel Solution Methods for Systems Arising from PDEs”, Luminy,
France, 16-20 September 2019

Numerical techniques for particle aggregation
6th IMPRS Summer School,
MPI for Dynamics of Complex Technical Systems, Magdeburg, 27. August,
2019

Vorstellung der Graduierten-Schule DASHH
VDI-Abendvortrag in der Reihe
“Datenwissenschaften in Akademie und Industrie”, 15 August, 2019, Helmut-Schmidt-Universität, Hamburg

Factorization and Symmetrization of stabilized Gaussian RBFs
Kolloquiumsvortrag an der TUHH, 11 July, 2019

Fast direct solvers for multilevel RBF interpolation problems
Computational Science & Engineering (CSE) Workshop Plön, March 26-28, 2019

Hierarchical matrices in stable radial basis interpolation
Minisymposium presentation at the SIAM Conference on Computational Science and Engineering,
Spokane, USA, Feb 25 - Mar 1, 2019

Fast direct solvers for RBF interpolation problems
Colloquium at the University Düsseldorf, January 25, 2019

## 2018

Iterative solvers for RBF interpolation problems
Colloquium at the University Chemnitz, November 30, 2018

Fast solvers for RBF interpolation problems
Invited plenary presentation, Conference on Fast Direct Solvers, Purdue University, Nov. 9-11, 2018

Iterative solvers for RBF interpolation problems
Colloquium at the Tennessee Technological University, Cookeville, TN, USA, November 8, 2018

Reducing computational complexity (using H-arithmetic) in RBF applications
International Conference on Spectral and High Order Methods (ICOSAHOM), Imperial College London, United Kingdom, 9-13th July 2018

(H-matrices for) Stable computations in RBF interpolation problems
Minisymposium presentation at the SIAM Conference on APPLIED LINEAR ALGEBRA, Hong Kong Baptist University, May 4-8, 2018

Toward stable computations in RBF interpolation problems
Computational Science & Engineering (CSE) Workshop Plön, 27.-29.3.2018

## 2017

Comparison of analytically and algebraically constructed low rank approximations in kernel-based scattered data interpolation
ÖMG-DMV Tagung, 11.-15. September 2017, Salzburg

Comparison of analytically and algebraically constructed low rank approximations in kernel-based scattered data interpolation
Minisymposium presentation at the International Conference On Preconditioning Techniques For Scientific And Industrial Applications 2017, Vancouver, Canada, 31.7. - 2.8.2017

Reducing computational complexity in scattered data interpolation
Workshop on Computational Science and Engineering, Plön, 22. - 24.3.2017

Hierarchical Matrices in Scattered Data Approximation
SIAM Conference on Computational Science and Engineering, Atlanta, Feb 27 - Mar 3, 2017

## 2016

Hierarchical Matrices in Scattered Data Approximation
Invited Colloquium at the Technical University of Munich, 23.11.2016

Hierarchical Matrices in Scattered Data Approximation
Workshop on "Fast solvers for highly oscillatory problems", Oberwolfach, 3.11.2016,

Tanz elektrischer Ströme und Musik von Radiowellen: Vom Experiment zur Computer-Simulation
Gemeinsamer Vortrag mit Prof. Christian Schuster an der TUHH im Rahmen der Ringvorlesung Technomathematik, 6. Juli 2016

Hierarchical matrices in scattered data approximation with radial basis functions
Norddeutsches Kolloquium at the University of Lübeck, April 22-23, 2016

Hierarchical matrices in scattered data approximation
Keynote speaker of Section 17 "Applied and Numerical Linear Algebra"
at the 87th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM)

2016, March 7-11, 2016, Braunschweig

2016, March 7-11, 2016, Braunschweig

## 2015

Hierarchical matrix factorization of the inverse.
Lothar-Collatz-Seminar, University Hamburg, December 3, 2015

Al Capone, Sherlock Holmes und Mathematik.
Public presentation at the "Tag der Mathematik", Universität Hamburg, November 14, 2015

Kann ein Computer rechnen?
Public presentation at the "Nacht des Wissens", Hamburg University of Technology, November 7, 2015

Hierarchical matrix factorization of the inverse.
Minisymposium presentation at the SIAM Conference on Applied Linear Algebra, Atlanta, October 26-30, 2015

3-d shape reconstruction based on 2-d projections of KDP crystals.
Kolloquiumsvortrag an der Tennessee Technological University, Cookeville, TN, USA, Oktober 22, 2015

H-FAINV: Hierarchically Factored Approximate Inverse Preconditioners.
GAMM Workshop on Applied and Numerical Linear Algebra, Max-Planck-Institute for dynamics of complex technical systems, Magdeburg, July 9-10, 2015

H-FAINV: Hierarchically Factored Approximate Inverse Preconditioners.
Conference on Numerical Algebra, Matrix Theory, Differential-Algebraic Equations, and Control Theory, Berlin, May 6-9, 2015 (poster presentation)

Numerical techniques for aggregation integrals in population balance systems.
Norddeutsches Kolloquium at the Jacobs University, Bremen, April 24-25, 2015

Numerische Lösungsverfahren für Aggregationsintegrale in Populationsbilanzsystemen.
Kolloquium an der Christian-Albrechts-Universität zu Kiel, February 12, 2015

## 2014

Kann ein Computer rechnen?
Presentation at the "Tag der Mathematik", Hamburg, November 22, 2014

Hierarchical Factored Approximate INVerse preconditioners: H-FAINV
European Multigrid Conference, Leuven, Belgien, September 9-12, 2014

Hierarchical Preconditioners for High-Order FEM
Householder Symposium XIX, Spa, Belgien, June 8-13, 2014 (poster presentation)

Preconditioning sparse grad-div/augmented Lagrangian stabilized saddle point problems
Norddeutsches Kolloquium über Angewandte Analysis und Numerische Mathematik, Kiel, May 9, 2014

## 2013

Preconditioning reduced grad-div stabilized incompressible flow problems
Invited presentation at the International Symposium on Numerics and Scientific Computing, Bruchsal, October 22-24, 2013

Hierarchical preconditioners for higher-order FEM.
Contributed talk at the International Conference on Domain Decomposition Methods (DD22), Universitdella Svizzera italiana - Lugano, Switzerland, September 16-20, 2013

Hierarchical preconditioners for higher-order FEM.
Contributed talk at the GAMM Workshop on Applied and Numerical Linear Algebra, Wuppertal, September 9-10, 2013

Numerical solution methods for coupled population balance systems for the dynamic simulation of multivariate particle processes at the example of shapeselective crystallization.
Project overview at the Kick-off meeting DFG-SPP 1679 "DynSim-FP", Hamburg, August 29, 2013

Hierarchical preconditioners for higher-order FEM.
Invited participant in a minisymposium on "Developments in Preconditioners and Iterative Methods for Linear Systems" at the 25th Biennial Numerical Analysis Conference, Glasgow, UK, June 25-28, 2013

Lösen linearer Gleichungssysteme in der Simulation von Strömungen
Invited presentation within the public lecture series "Mathematische Modellierung in den Natur-, Technik- und Gesellschaftswissenschaften" at the Lothar Collatz Center for Computing Science, University Hamburg, June 4, 2013 (Folien, PDF, 19.464KB)

## 2012

Hierarchical matrices: Some theory and some applications in preconditioning discretized fluid flow problems.
Invited colloquium talk at the Weierstrass Institute for Applied Analysis and Stochastics, Berlin, October 9, 2012

Hierarchical matrices: past, present, and future.
Invited keynote speaker at the “Scalable Hierarchical Algorithms for eXtreme Computing” workshop (SHACS) at the King Abdullah University of Science and Technology, Thuwal, Saudi Arabia, April 28-30, 2012

Hierarchical matrices: a brief history and some applications in numerical PDEs
Invited colloquium talk at the University of Houston, Texas, April 19, 2012

## 2011

Hierarchical preconditioners for higher-order FEM.
Invited colloquium talk at Purdue University, Indiana, Nov. 9, 2011 May 22-28, 2011

One-step hierarchical preconditioners for higher order FEM.
Funded participant at the Workshop on “Fast solvers for partial differential equations”, Mathematisches Forschungsinstitut Oberwolfach, May 22-28, 2011

Block preconditioners for saddle point problems.
Invited participant at a minisymposium at the SIAM Computational Science and Engineering Conference in Reno, NV, February 28 - March 4, 2011

Numerical simulation of fluid flow.
Invited presentation at the TTU chapter of Sigma Xi at their luncheon seminar on February, 24, 2011.

Hierarchische Matrizen und ihre Anwendungen in der numerischen Strömungssimulation.
Invited colloquium at the University of Lübeck, Germany, January 21, 2011

Hierarchische Matrizen und ihre Anwendungen in der numerischen Strömungssimulation.
Invited colloquium at the Leuphana University Lüneburg, Germany, January 20, 2011

## 2010

Poster Title: H-LU factorization of Stabilized Saddle Point Problems.
Funded participant at the Workshop on "Numerical Solutions of Partial Differential Equations: Fast Solution Techniques", Institute for Mathematics and Its Applications (IMA) at the University of Minnesota, MN, November 29 - December 3, 2010.

Hierarchische Matrizen und ihre Anwendungen in der numerischen Strömungssimulation.
Invited seminar presentation at the Hamburg University of Technology, Germany, November 11, 2010

DAAD Alumni Meeting: "Facing the four Elements: Developing a Transatlantic Approach to Sustainability".
October 28-30, 2010, New York City (funded participant)

Attended the Scientific Computing Seminar with emphasis on "Numerical methods for partial differential equations in Eart Sciences".
June 28-30, 2010, Kiel, Germany

Blockpräkonditionierer für Sattelpunktprobleme.
(Invited) seminar presentation at the University of Karlsruhe, Germany, June 8-10, 2010

Funded participant at the Workshop on "Computational optimization for tensor decompositions"
American Institute of Mathematics (AIM), Palo Alto, CA, March 29-April 2, 2010.

Attended the GAMM Seminar on Tensor Approximations and High-Dimensional Problems.
Max-Planck-Institute for Mathematics in the Sciences, Leipzig, Germany, February 22-25, 2010

## 2009

Hierarchische Matrizen und ihre Anwendungen in der numerischen Strömungssimulation.
Seminar presentation at the Ernst Moritz Arndt University Greifswald, Germany, November 14, 2009

Hierarchical matrix preconditioners.
SIAM Conference on Applied Linear Algebra, Monterey, CA, October 25-30, 2009 (invited to present at the minisymposium on Quasiseparable Matrices and Polynomials)

Hierarchical matrices and their use in preconditioners for saddle point problems.
University of Kentucky, Lexington, invited colloquium talk, October 1, 2009

An Implicit Approximate Inverse Preconditioner for Saddle Point Problems.
International Conference on Preconditioning Techniques for Scientific and Industrial Applications, Hong Kong Baptist University, August 24-26, 2009

Algebraic hierarchical matrix preconditioners for saddle point problems.
Workshop on "Advances and perspectives on numerical methods for saddle point problems", Banff International Research Station, Canada, April 12-17, 2009 (invited)

## 2008

Blackbox versus geometric methods to construct H-matrices.
Mathematics Graduate Seminar, Tennessee Technological University, November 13, 2008

Blackbox H-preconditioners for two- and three-dimensional saddle point problems.
9th European Multigrid conference, Bad Herrenalb, October 2008, invited plenary lecture

Preconditioned nullspace method for the Oseen problem.
Mathematisches Forschungsinstitut Oberwolfach, Workshop on "Iterative solvers for partial differential equations", May 18-24, 2008 (invited)

Approximate LU and inverse preconditioners for saddle point problems.
Oak Ridge National Lab, invited colloquium talk and collaborative meeting on April 24, 2008

H-matrix preconditioners for the Navier-Stokes equations.
Clemson University, Clemson, SC, invited colloqium talk on March 27, 2008

## 2007

H-matrix preconditioners for the Navier-Stokes equations.
6th International Congress on Industrial and Applied Mathematics (ICIAM), Zürich, July 2007 (invited to present at the minisymposium on saddle point problems)

Numerical Simulation - Theory and Application.
Poster presentation at the DAAD Pan-American conference in Sao Paulo, Brazil, June 2007

Hierarchical matrix preconditioners for the Oseen equations.
Invited seminar at the University of Lübeck, Germany, April 2007

Discrete divergence-free basis through H-QR factorization.
Invited seminar at the University of Bath, UK, March 2007

## 2006

Iterative solvers in the simulation of incompressible fluid flow.
Graduate seminar at Tennessee Technological University, October 2006

Domain-decomposition based joint H-matrix preconditioners for saddle point problems.
17th International Conference on Domain DecompositionMethods, Strobl/St. Wolfgang, Austria, July 2-8, 2006.

Block and joint H-matrix preconditioners for the Oseen equations.
2006 Annual GAMM Conference, Berlin, Germany, March 27-31, 2006.

## 2005

Hierarchical matrix preconditioners for saddle point problems.
8th European Multigrid Conference, Scheveningen, The Netherlands, September 27-30, 2005

Hierarchical matrix preconditioners for saddle point problems.
Invited colloquium talk at the Max-Planck-Institute for Mathematics in the Sciences, Leipzig (Germany), July 2005

Efficient preconditioners and hierarchical matrices.
Invited plenary presentation at the 2005 International Conference On Preconditioning Techniques For Large Sparse Matrix Problems In Scientific And Industrial Applications, Emory University, Atlanta, May 2005

Efficient preconditioners and H-matrices.
Invited colloquium at Oak Ridge National Lab, Computer Science and Mathematics Division, April 2005

Fast solvers through domain decomposition and hierarchical matrices.
Mathematical Graduate Seminar at Tennessee Technological University, Cookeville (USA), February 2005

Domain decomposition based hierarchical matrix preconditioners.
16th International Conference on Domain Decomposition Methods, New York, January 2005