Symplectic eigenvalue problem via trace minimization and Riemannian optimization

Nguyen, Thanh Son;Absil, Pierre-Antoine;Gao, Bin;Stykel, Tatjana
(2021) SIAM Journal on Matrix Analysis and Applications — Vol. 42, n° 4, p. 1732-1757 (2021)

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  • Nguyen, Thanh Sonorcid-logoUCLouvain
    Author
  • Author
  • Gao, Binorcid-logoUCLouvain
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  • Stykel, Tatjanaorcid-logo
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Abstract
We address the problem of computing the smallest symplectic eigenvalues and the corresponding eigenvectors of symmetric positive-definite matrices in the sense of Williamson’s theorem. It is formulated as minimizing a trace cost function over the symplectic Stiefel manifold. We first investigate various theoretical aspects of this optimization problem such as characterizing the sets of critical points, saddle points, and global minimizers as well as proving that non-global local minimizers do not exist. Based on our recent results on constructing Riemannian structures on the symplectic Stiefel manifold and the associated optimization algorithms, we then propose solving the symplectic eigenvalue problem in the framework of Riemannian optimization. Moreover, a connection of the sought solution with the eigenvalues of a special class of Hamiltonian matrices is discussed. Numerical examples are presented
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Citations

Nguyen, T. S., Absil, P.-A., Gao, B., & Stykel, T. (2021). Symplectic eigenvalue problem via trace minimization and Riemannian optimization. SIAM Journal on Matrix Analysis and Applications, 42(4), 1732-1757. https://doi.org/10.1137/21m1390621 (Original work published 2021)