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MathGroup Archive 2004

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Eigensystem: different solution in V5.0 and V4.1 ??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48291] Eigensystem: different solution in V5.0 and V4.1 ??
  • From: ivo.bleylevens at facburfdaw.unimaas.nl (Ivo bleylevens)
  • Date: Sat, 22 May 2004 03:04:22 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello all !

I am a dutch PhD student at the University of Maastricht and I have a
question about some strange behaviour of the Mathematica's 5.0
function Eigensystem[]. I have an 512x512 non-symmetric complex matrix
M. When i use the command eigsys = Eigensystem[M] in Mathematica 5.0,
the eigenvalues were not the eigenvalues I expected ! I calculated
exactly the same notebook in Mathematica version 4.1 and these
eigenvalues look the same as the wanted eigenvalues !! Am i doing
something wrong in version 5.0 ??

* I already tried to use the options of Eigensystem[] described at
http://documents.wolfram.com/v5/Built-inFunctions/AdvancedDocumentation/LinearAlgebra/4.4.html
but that also didn't help.

* I tried to set the precision of Mathematica 5.0 with the command
eigsys = Eigensystem[N[M, 30]] but that didn't help either !

* I also calculated the eigenvalues of the matrix M with another system using
the functions EIG and EIGS (which makes use op the LAPACK functions.
Mathematica 5 uses this functions also as described in the link
above). The eigenvalues computed with this two functions are exactly
similar with the eigenvalues calculated in Mathematica 4.1....

So in my opinion Mathematica 5.0 produces incorrect
eigenvalues......can someone help me ???

Ivo Bleylevens
Universiy of Maastricht


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