MatrixExp[DiagonalMatrix[{1,1,-1,-1}]] & MMA 3.0

• To: mathgroup at smc.vnet.net
• Subject: [mg7617] MatrixExp[DiagonalMatrix[{1,1,-1,-1}]] & MMA 3.0
• From: Robert Prus <robert at fuw.edu.pl>
• Date: Thu, 19 Jun 1997 15:53:33 -0400 (EDT)
• Organization: Warsaw University, Physics Department
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

I discovered that MatrixExp[] command in Mathematica 3.0 gives wrong results.

Here are two examples of using MatrixExp[] with two versions of Mathematica
(2.2 and 3.0):

Mathematica 2.2 for SPARC
-- Terminal graphics initialized --

In[1]:= MatrixExp[DiagonalMatrix[{1,1}]]

Out[1]= {{E, 0}, {0, E}}

In[2]:= MatrixExp[DiagonalMatrix[{-1,-1}]]

1          1
Out[2]= {{-, 0}, {0, -}}
E          E

In[3]:= MatrixExp[DiagonalMatrix[{1,1,-1,-1}]]

1                1
Out[3]= {{E, 0, 0, 0}, {0, E, 0, 0}, {0, 0, -, 0}, {0, 0, 0, -}}
E                E

Mathematica 3.0 for Solaris
-- Terminal graphics initialized --

In[1]:= MatrixExp[DiagonalMatrix[{1,1}]]

Out[1]= {{E, 0}, {0, E}}

In[2]:= MatrixExp[DiagonalMatrix[{-1,-1}]]

1          1
Out[2]= {{-, 0}, {0, -}}
E          E

In[3]:= MatrixExp[DiagonalMatrix[{1,1,-1,-1}]]

1                1
Out[3]= {{-, 0, 0, 0}, {0, -, 0, 0}, {0, 0, E, 0}, {0, 0, 0, E}}
E                E

Mathematica 3.0 gives wrong result for last calculation, i.e.
MatrixExp[DiagonalMatrix[{1,1,-1,-1}]] while MMA 2.2 gives correct result.

Any ideas for solving that problem?

RP

--
Robert Prus, robert at fuw.edu.pl
Institute of Theoretical Physics, Warsaw University
Hoza 69, 00-681 Warsaw, Poland
tel./fax (48)(2) 6214397

```

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