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I am trying to solve system of 15 differential equations:

eqdiffu1 = 
  {D[yu, t] == bu, D[yd, t] == bd, 
   D[yl, t] == yl*(-sumg3[t] + 3yd.yd + 4 yl.yl), 
   D[vckm, t] == -ConjugateTranspose[elu].vckm +  vckm.eld, 
   (vckm /. {t -> 0}) == vckm1, 
   yu1[0] == yg2, yu2[0] == ys2, yu3[ttop] == yt2,  yd1[0] == ydo2,  yd2[0] == yc2, 
   yd3[0] == yb2, yl1[0] == yel2, yl2[0] == ym2, yl3[0] == ytau2};

with

sol = 
  NDSolve[
   eqdiffu, 
   {v11[t], v12[t], v13[t], 
    v21[t], v22[t], v23[t], 
    v31[t], v32[t], v33[t], 
    yu1[t], yu2[t], yu3[t] , 
    yd1[t], yd2[t], yd3[t], 
    yl1[t], yl2[t], yl3[t]}, 
   {t, 0, 0.21}];

where yu, yd, yl are vectors and vckm and elu are matrices.

Mathematica produces the error messages:

Power::infy: Infinite expression 1/0. encountered.
Infinity::indet: Indeterminate expression 0. ComplexInfinity encountered.
Infinity::indet: Indeterminate expression 0. ComplexInfinity encountered.
Power::infy: Infinite expression 1/0. encountered.
General::stop: Further output of Power::infy will be suppressed during this calculation.
NDSolve::ndnum: Encountered non-numerical value for a derivative at t == 0.`.

I am sure there are no infinities in a denominator. Do you know where there could be a mistake?

Please, help me.

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  • $\begingroup$ Maria, you'd need to include everything (all variable definitions, etc) for anyone to be able to help. $\endgroup$ – user21 Jul 10 '18 at 9:43
  • $\begingroup$ There are several issues here. yu, yd etc..do they depend on t ? Otherwise D[yu, t] gets evaluated to 0. Also you have yd.yd. Is this supposed to be a Dot product ? $\endgroup$ – Lotus Jul 10 '18 at 9:43
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    $\begingroup$ Let's hold off with down votes until new people get a chance to accustom them self. $\endgroup$ – user21 Jul 10 '18 at 9:47
  • $\begingroup$ Thank you for your advices, I will edite it soon. yd, yu etc. depend on t, yd.yd is suppposed to be a dot product. $\endgroup$ – Maria Dawid Jul 10 '18 at 10:23
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    $\begingroup$ Maria, (1) you formulated the system entitled eqdiffu1, while you then solve eqdiffu. This may be an error. (2) As soon as yd.yd is supposed to be a dot product, that means that yd (and also yl) are supposed to be vectors. Mma, however, does not know that. A good idea would be to either write equations separately for each component, or to inform Mma about their vector origin. The latter may be done by starting the code with making a definition, like yd[t_]:={yd1[t], yd2[t]}. This is in the case of a 2D vector yd[t]. Analogously you may try in a more complex case. $\endgroup$ – Alexei Boulbitch Jul 10 '18 at 11:58

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