Eigensystem ignoring assumptions
- To: mathgroup at smc.vnet.net
- Subject: [mg132281] Eigensystem ignoring assumptions
- From: Abced Def <ffcitatos at gmail.com>
- Date: Thu, 30 Jan 2014 23:04:40 -0500 (EST)
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- Delivered-to: l-mathgroup@wolfram.com
- Delivered-to: mathgroup-outx@smc.vnet.net
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Hi,
I am trying to understand, why Eigensystem is ignoring the assumptions and
still dividing by something that is explicitly assumed to be zero. This is
a more extreme counterpart of the b>=0 case. Any comments or references to
the documentation are appreciated.
In[320]:= Clear["Global`*"]
In[321]:= $Assumptions = b == 0;
In[322]:= m1 = ({
{a, b},
{b, -a}
});
In[323]:= Eigensystem[m1]
Out[323]= {{-Sqrt[a^2 + b^2], Sqrt[
a^2 + b^2]}, {{-((-a + Sqrt[a^2 + b^2])/b),
1}, {-((-a - Sqrt[a^2 + b^2])/b), 1}}}