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Re: Eigensystem applied to a unitary matrix crashes Mathematica 4.

• To: mathgroup at smc.vnet.net
• Subject: [mg21384] Re: Eigensystem applied to a unitary matrix crashes Mathematica 4.
• From: Jos Bergervoet <bergervo at iaehv.iae.nl>
• Date: Sat, 1 Jan 2000 20:54:43 -0500 (EST)
• Organization: Internet Access Eindhoven, the Netherlands
• References: <831tqg$fmh@smc.vnet.net> <83cn2s$5o2$8@dragonfly.wolfram.com> <83ncc5$5ph$4@dragonfly.wolfram.com> <844cf2$jp2@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

John A. Sidles <sidles at u.washington.edu> wrote:
>   ...
> Eigensystem[] documentation might reasonably be revised to
> be a little more forthcoming about these behaviors, which
>   ...

Is this a problem only when the matrix is (near) degenerate?
Or, more precisely, if the eigenvalues are different by many
significant digits, can I be sure then that Eigensystem[] will
return orthogonal vectors?

> over the years have taken so many users by surprise.

And it is only to avoid any more surprises that I try to find
out what the exact behavior is.

-- Jos