Re: Running problem in DSolve

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• Subject: [mg132158] Re: Running problem in DSolve
• From: "Kevin J. McCann" <kjm at KevinMcCann.com>
• Date: Mon, 6 Jan 2014 02:30:54 -0500 (EST)
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```Not an expert; however, I ran this on my computer for about 15 minutes.
It used about 3Gb of memory, but never got to an answer. Could you do a
numerical integration? For example, choose values for the constants
a,b,... and then use NIntegrate. At least this would give you a look at
the kind of answers to expect.

Alternatively, if you can diagonalize the RHS, i.e. derivative==RHS,
then, if this new set of equations can be solved for the eigenfunctions,
you could map this back to AA,EE, ... I don't have time to try this just
now, but may later.

Kevin

On 1/5/2014 5:25 AM, saha18swarup at gmail.com wrote:
> Dear Expert,
> I have some problem running Mathematica  and it is taking too much time. Can you help me?
>
> Regards
> Swarup
>
> eqns = {AA'[x] + I*b*EE[x] + c*CC[x] + d*AA[x] == 0,
>    BB'[x] - a*CC[x] + I*b*FF[x] - c*DD[x] + d*BB[x] == 0,
>    CC'[x] + a*BB[x] + I*b*GG[x] + c*AA[x] + d*CC[x] == 0,
>    DD'[x] + I*b*HH[x] - c*BB[x] + d*DD[x] == 0,
>    EE'[x] + I*b*AA[x] - c*GG[x] - I*e*BB[x] + d*EE[x] == 0,
>    FF'[x] - a*GG[x] + I*b*BB[x] + c*HH[x] - I*e*AA[x] + d*FF[x] == 0,
>    GG'[x] + a*FF[x] + I*b*CC[x] - c*EE[x] - I*e*DD[x] + d*GG[x] == 0,
>    HH'[x] + I*b*DD[x] + c*FF[x] - I*e*CC[x] + d*HH[x] == 0}
>
> ic = {AA[0] == 1, BB[0] == 0, CC[0] == 0, DD[0] == 0, EE[0] == 1,
>    FF[0] == 0, GG[0] == 0, HH[0] == 0}
>
> DSolve[{eqns, ic}, {AA, BB, CC, DD, EE, FF, GG, HH}, x]
>

```

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