       Re: NDSolve problem

• To: mathgroup at smc.vnet.net
• Subject: [mg101676] Re: NDSolve problem
• From: Simon <simonjtyler at gmail.com>
• Date: Tue, 14 Jul 2009 05:34:47 -0400 (EDT)
• References: <h3cfav\$ic8\$1@smc.vnet.net>

```Hi Haibo

Mathematica does not have built in support for abstract linear algebra
quantities, so if something is a vector or a matrix then you have to
give it components.
Define (for example)
e1[t_] := {e11[t], e12[t], e13[t], e14[t]}
e2[t_] := {e21[t], e22[t], e23[t]}
\[CurlyTheta][t_] := {\[CurlyTheta]1[t], \[CurlyTheta]2[t], \
[CurlyTheta]3[t]}

Then, the second problem with your code is that the matrices S, G and
J are 3x3, whilst EE is a 4x4 -- you seem to be mixing these in your
differential equations.
For example, the first line in your NDSolve is
J.e2'[t] == -kq Transpose[EE[e1[t]]].e1[t]-...
on the RHS you have a 4-vector minus a whole heap of 3-vectors, on the
LHS a 3-vector.

Fix these two problems and it should all work....

Simon

```

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