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When I evaluate the code shown below, it gives an error:

NDSolve::ndsz: At x == -0.00001, step size is effectively zero; singularity or stiff system suspected.

W := (2*Pi*3*10^14)
CC := 3*10^8
vt := ((2*T/me)^(1/2))
me := 9.11*10^-31
T := 1.6*10^-15
Wc := 1.6*10^-19/me
L := 0.00001
wp := W*Sqrt[(1 - x/L)]
Om := Wc
e0 := 8.85*10^-12
LnLumbda := 10
k := W/CC (1 - (1 - x/L)/(1 + (Wc)/W))^(1/2)
R := ((1 - x/L)*W^2*(1.6*10^-19)^2*Pi*Sqrt[me]*LnLumbda)/( T^(3/2)*e0)
q := (W + 2 I R - Om)/vt 
F := q/k
sol = 
  NDSolve[
    {(y''[x] + 
      (W^2/ (CC^2) + ((W (wp)^2)/((CC^2) vt k )) 
        ((E^-F^2 (-π Erfi[F] + Log[-(1/F)] + Log[F]))/Sqrt[π])) y[x]) == 0, 
     y'[-L] == 0, y[-L] == 10}, 
    y, {x, -L, L}]

I will appreciate any help.

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closed as unclear what you're asking by Sektor, LCarvalho, b3m2a1, MarcoB, Öskå Dec 13 '17 at 17:23

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    $\begingroup$ So what's the problem? 1. Does the equation/system of equation actually have solution? 2. Can you get the solutions? $\endgroup$ – user202729 Dec 4 '17 at 6:23
  • $\begingroup$ Are you sure, that your parameter definitions are right? With q you introduce the imaginary unit I. Plot the cofactor to y[x] in your diffequation to see it's highly oscillatory and complex for x<0. $\endgroup$ – Akku14 Dec 4 '17 at 7:42
  • $\begingroup$ After solving the code, it's error has:NDSolve::ndsz: At x == -0.00001, step size is effectively zero; singularity or stiff system suspected $\endgroup$ – Nagi Dec 5 '17 at 9:50
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After evaluating your constants, a compute of your ode:

y''[x] + (W^2/(CC^2) + ((W (wp)^2)/((CC^2) vt k)) ((E^-F^2 (-π Erfi[F] + Log[-(1/F)] + Log[F]))/Sqrt[π])) y[x] == 0 // N // Chop

yields

y[x] (-((∞ (1. - 100000. x))/Sqrt[Sign[1. - 0.999907 (1. - 100000. x)]]) + 3.94784*10^13) + (y^′′)[x] == 0

The infinity is the problem. Rationalizing your data and increasing the WorkingPrecision did not help.

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  • $\begingroup$ so what does it mean? do I change the parameters or other things? $\endgroup$ – Nagi Dec 5 '17 at 10:03
  • $\begingroup$ Your data is way to jumpy for NDSolve to handle. Rationalize your values and plot the coefficient of y[x] in your ode from -L to L to see what I mean. You need a much smoother function than what you have. $\endgroup$ – Bill Watts Dec 5 '17 at 23:13
  • $\begingroup$ Thankful.Regards. $\endgroup$ – Nagi Dec 7 '17 at 5:18

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