Trail to a Lyapunov equation solver

  • Authors:
  • Eugene L. Wachspress

  • Affiliations:
  • 49 Meadow Lakes 07, Hightstown, NJ 08520, United States

  • Venue:
  • Computers & Mathematics with Applications
  • Year:
  • 2008

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Abstract

The Lyapunov matrix equation AX+XA^@?=B is N-stable when all eigenvalues of the real nxn matrix A have positive real part. When the real nxn matrix B is spd the solution X is spd. It is of low rank when B=CC^@? where C is nxr with r@?n. An efficient algorithm has been found for solving the low-rank equation. This algorithm is a result of over fifty years of research starting with seemingly unrelated development of alternating direction implicit (ADI) iterative solution of elliptical systems. The low rank algorithm may be applied to a full rank equation if one can approximate the right-hand side by a sum of low rank matrices. This may be attempted with the Lanczos algorithm.