Unit

Numerical Algorithms and High-Performance Computing - CADMOS Chair

Laboratory

Related publications (333)

Perturbation bounds for isotropic invariant subspaces of skew-Hamiltonian matrices

We investigate the behavior of isotropic invariant subspaces of skew-Hamiltonian matrices under structured perturbations. It is shown that finding a nearby subspace is equivalent to solving a certain quadratic matrix equation. This connection is used to de ...

Society for Industrial and Applied Mathematics2005

Low Rank Updates for the Cholesky Decomposition

Matthias Seeger

Usage of the Sherman-Morrison-Woodbury formula to update linear systems after low rank modifications of the system matrix is widespread in machine learning. However, it is well known that this formula can lead to serious instabilities in the presence of ro ...

2004

On the condition of a complex eigenvalue under real perturbations

Daniel Kressner

We investigate the condition number for a complex eigenvalue of a real matrix under real perturbations. Based on an explicit formula, it is shown that this number is never smaller than 1/root2 times the corresponding condition number with respect to comple ...

2004

Efficient scattering calculations in complex backgrounds

Olivier Martin

The utilization of the Green's tensor associated with a complex optical background (surface, cavity or stratified medium) leads to a dramatic reduction of the computation effort associated with scattering calculations in that background. This approach is i ...

2004

A dynamic preconditioner for Newton-Krylov algorithms. Application to fluid-structure interaction

Simone Deparis

We consider linear and nonlinear convergence acceleration techniques in the framework of Newton or inexact Newton methods. The proposed procedure is based on a new dynamic preconditioner to be used in combination with the GMRES method for reducing the cost ...

2004

Determination of chemical shift anisotropy tensors of carbonyl nuclei in proteins through cross-correlated relaxation in NMR

Geoffrey Bodenhausen

The principal components and orientations of the chem. shift anisotropy (CSA) tensors of nearly all 13C carbonyl nuclei in a small protein have been detd. in isotropic soln. by a combination of three complementary cross-correlation measurements. [on SciFin ...

2004

Anneau de Witt des G-formes et multiples de G-formes trace

Philippe Chabloz

This thesis deals with the study of G-forms and particulary the trace form of a G-Galois algebra. Let k be a field of characteristic not two. Let G be a finite group and L a G-Galois algebra over k. We define the trace form qL by qL(x, y) = TrL/k(xy) for a ...

EPFL2004

Induced magnetic fields in aromatic [n]-annulenes-interpretation of NICS tensor components

The components of nucleus-independent chem. shift (NICS) tensors for Dnh n-annulenes are discussed as indexes of the arom. character of electronic pi systems. The component corresponding to the principal axis perpendicular to the ring plane, NICSzz, is fou ...

2004

An exact Block-Newton algorithm for solving fluid-structure interaction problems

In this Note, we introduce a partitioned Newton based method for solving nonlinear coupled systems arising in the numerical approximation of fluid-structure interaction problems. The originality of this Schur-Newton algorithm lies in the exact Jacobians ev ...

2003

Block algorithms for orthogonal symplectic factorizations

Daniel Kressner

On the basis of a new WY-like representation block algorithms for orthogonal symplectic matrix factorizations are presented. Special emphasis is placed on symplectic QR and URV factorizations. The block variants mainly use level 3 (matrix-matrix) operation ...

2003