A polynomial-time algorithm for the jacobson form of a matrix of ore polynomials

  • Authors:
  • Mark Giesbrecht;Albert Heinle

  • Affiliations:
  • Cheriton School of Computer Science, University of Waterloo, Canada;Lehrstuhl D für Mathematik, RWTH Aachen University, Aachen, Germany

  • Venue:
  • CASC'12 Proceedings of the 14th international conference on Computer Algebra in Scientific Computing
  • Year:
  • 2012

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Abstract

We present a new algorithm to compute the Jacobson form of a matrix A of polynomials over the Ore domain F(z)[x;σ,δ]n×n, for a field F. The algorithm produces unimodular U, V and the diagonal Jacobson form J such that UAV=J. It requires time polynomial in degx(A), degz(A) and n. We also present tight bounds on the degrees of entries in U, V and J. The algorithm is probabilistic of the Las Vegas type: we assume we are able to generate random elements of F at unit cost, and will always produces correct output within the expected time. The main idea is that a randomized, unimodular, preconditioning of A will have a Hermite form whose diagonal is equal to that of the Jacobson form. From this the reduction to the Jacobson form is easy. Polynomial-time algorithms for the Hermite form have already been established.