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NDSolve&MaxSteps

  • To: mathgroup at smc.vnet.net
  • Subject: [mg38696] NDSolve&MaxSteps
  • From: "extrabyte" <extrabyte at NSP.it>
  • Date: Mon, 6 Jan 2003 03:42:22 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello!

[(I do not speak English well;(]

I have the following set


eq1= x''[z]+A[z] x'[z] + B1[z] x[z] - W[z] y[z]==0;
eq2= y''[z]+A[z] y'[z] + B2[z] y[z] - W[z] x[z]==0;

Here z is an dimensionless variable.
Moreover:
**************************************************
A[z_]: = (1+z)^-1

F1[z_]: =NIntegrate[y^4/((1+y^2 (1+z)^2) (Exp[Sqrt[1+y^2]]+1)),{y,0, +oo},
WorkingPrecision -> 15, AccuracyGoal -> 20, MinRecursion -> 3,
MaxRecursion ->10]

F2=NIntegrate[y^2/(Exp[Sqrt[1+y^2]]+1),{y,0, +oo}, WorkingPrecision -> 15,
AccuracyGoal -> 20, MinRecursion -> 3, MaxRecursion ->10]


B1[z_]: =(1+z) Sqrt[F1[z]/F2]

B2[z_]: =(1+z)

W[z_]: =(1+z)^-3

******************************************************************

My input is:

sol=NDSolve[{eq1, eq2, x'[1300] == 0, x[1300] == 1, y'[1300] == 0,
  y[1300] == 1}, {x, y}, {z, 0, 1300}, MaxSteps -> 2000]

The output is:

{{x -> InterpolatingFunction[{{1292.09, 1300.}}, "<>"],
    y -> InterpolatingFunction[{{1292.09, 1300.}}, "<>"]}

But I need solutions for z=0-1300.... Increase MaxSteps?

Thanx:-)


Best regards
--
extrabyte



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