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- D. Steven Mackey, Niloufer Mackey, Christian Mehl, Volker Mehrmann
- SIAM J. Matrix Analysis Applications
- 2006

Many applications give rise to nonlinear eigenvalue problems with an underlying structured matrix polynomial. In this paper several useful classes of structured polynomial (e.g., palindromic, even, odd) are identified and the relationships between them explored. A special class of linearizations that reflect the structure of these polynomials, and therefore… (More)

- D. Steven Mackey, Niloufer Mackey, Christian Mehl, Volker Mehrmann
- SIAM J. Matrix Analysis Applications
- 2006

The classical approach to investigating polynomial eigenvalue problems is lineariza-tion, where the polynomial is converted into a larger matrix pencil with the same eigenvalues. For any polynomial there are infinitely many linearizations with widely varying properties, but in practice the companion forms are typically used. However, these companion forms… (More)

of Berlin. In collaboration with the company SFE they study the resonances when rail tracks are excited by high speed trains, the goal being to reduce noise and vibrations in the trains. The new ICE trains travel across Europe at speeds as high as 300 km/h but the numerical methods used to design them are at least 30 years old. More often than not the… (More)

- D. Steven Mackey, Niloufer Mackey, Christian Mehl, Volker Mehrmann
- Numerical Lin. Alg. with Applic.
- 2009

We present structure-preserving numerical methods for the eigenvalue problem of complex palindromic pencils. Such problems arise in control theory, as well as from palindromic linearizations of higher degree palindromic matrix polynomials. A key ingredient of these methods is the development of an appropriate condensed form — the anti-triangular Schur form.… (More)

- Christian Mehl
- SIAM J. Matrix Analysis Applications
- 2000

In this paper we consider real or complex skew-Hamiltonian/Hamiltonian pencils λS − H, i.e., pencils where S is a skew-Hamiltonian and H is a Hamiltonian matrix. These pencils occur for example in the theory of continuous time, linear quadratic optimal control problems. We reduce these pencils to canonical and Schur-type forms under structure-preserving… (More)

Many applications give rise to matrix polynomials whose coefficients have a kind of reversal symmetry, a structure we call palindromic. Several properties of scalar palin-dromic polynomials are derived, and together with properties of compound matrices, used to establish the Smith form of regular and singular T-palindromic matrix polyno-mials over arbitrary… (More)

It is shown that, for any given polynomially normal matrix with respect to an indefinite inner product, a nonnegative (with respect to the indefinite inner product) invariant sub-space always admits an extension to an invariant maximal nonnegative subspace. Such an extension property is known to hold true for general normal matrices if the nonnegative… (More)

- Nicholas J. Higham, Christian Mehl, Françoise Tisseur
- SIAM J. Matrix Analysis Applications
- 2010

The polar decomposition of a square matrix has been generalized by several authors to scalar products on R n or C n given by a bilinear or sesquilinear form. Previous work has focused mainly on the case of square matrices, sometimes with the assumption of a Hermitian scalar product. We introduce the canonical generalized polar decomposition A = W S, defined… (More)

- Gregory Ammar, Christian Mehl, Volker Mehrmann
- 1999

We describe canonical forms for elements of a classical Lie group of matrices under similarity transformations in the group. Matrices in the associated Lie algebra and Jordan algebra of matrices inherit related forms under these similarity transformations. In general, one cannot achieve diagonal or Schur form, but the form that can be achieved displays the… (More)

- Christian Mehl
- SIAM J. Matrix Analysis Applications
- 2008

The asymptotic convergence behavior of cyclic versions of the nonsymmetric Jacobi algorithm for the computation of the Schur form of a general complex matrix is investigated. Similar to the symmetric case, the nonsymmetric Jacobi algorithm proceeds by applying a sequence of rotations that annihilate a pivot element in the strict lower triangular part of the… (More)