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MathGroup Archive 2000

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Re: NDSolve error message: Can't find starting value ...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23807] Re: NDSolve error message: Can't find starting value ...
  • From: Brian Higgins <bghiggins at ucdavis.edu>
  • Date: Sat, 10 Jun 2000 03:00:14 -0400 (EDT)
  • References: <8hfggl$i4h@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Axel,

You have  a second order ODE , but you specified BCs with
second derivatives. The BCs should be of lower order. For
example R'[-3]==0 and R'[3]==0 will work. Of course, the BCs are
dictated by tthe physics of the problem

Brian


n article <8hfggl$i4h at smc.vnet.net>,
  Axel Kowald <axel at itb.biologie.hu-berlin.de> wrote:
> Hello,
>
> I try to solve the following second order ODE with NDSolve
>
> NDSolve[{0 == R''[x] + DiracDelta[x] - R[x],         R''[-3] == 0,
> R''[3] == 0}, R, {x, -3, 3}]
>
> and I get the following error message:
>
> NDSolve::"ndsv": "Cannot find starting value for the variable x."
>
> I couldn't find any description of this message in the
Mathematica book, so I'm
> not sure what to do. I have a second order ODE with two
boundary
> conditions, what's missing ?
>
> Many thanks,
>
>                Axel Kowald
>
> P.S. Btw., this is done with Mathematica 4.
>
>


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