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I am trying to solve these two equations but find an error of fewer than the dependent variable and list of replacement rules nor a valid dispatch table, and so cannot be used for replacing. I don't know what should I do? If anyone can resolve this, will be appreciated.

A1 = 1;
B1 = 0;
del0 = 1.50;
g0 = .0003;
dela = -1.5;(*Subscript[\[CapitalDelta], L] ; Laser-Lower polariton \
detuning*)
ome = 3.014;
ome1 = .125;
k1 = 0.1;
P0 = 20;
kex = .02;
kL = (k1 + kex)/2 - del0*(k1 - kex)/(2*ome);
Gma = 0.0001;
sol = DSolveValue[{a1'[t] - I*dela*a1[t] - 
      I*g0*(1 - del0/ome)*A1*(b1[t] + Conjugate[b1[t]])/2*a1[t] - 
      I*P0*(1 - del0/(2*ome))/Sqrt[2] - 
      I*P0*g0*B1*((b1[t] + Conjugate[b1[t]])/2)/(Sqrt[2]*ome) + 
      kL/2*a1[t] + (k1 - kex)*g0/ome*B1*(b1[t] + Conjugate[b1[t]])/2*
       a1[t] == 0, 
    b1'[t] + I*ome1*b1[t] - I*g0*(1 - del0/ome)*A1*Abs[a1[t]]^2/2 - 
      I*P0*g0*B1*((a1[t] + Conjugate[a1[t]])/2)/(Sqrt[2]*ome) + 
      Gma*b1[t]/2 == 0, a1[t] == 1, b1[t] == 0}, a1, b1, t] // Chop
Plot[{Evaluate[Abs[a1[t]^2]] /. sol}, {t, 0, 500}]
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    $\begingroup$ A couple of obvious problems. If you are trying to solve differential equations for a1[t] and b1[t] then giving it initial conditions a1[t]==1,b1[t]==0 sort of defeats the process. Probably you meant a1[0]==1,b1[0]==0 or something similar. Next, you finish up your DSolveValue with ...a1,b1,t] and that almost certainly needs to be ...{a1,b1},t] Next, for DSolve and DSolveValue giving it exact rational constants often enables it to select more powerful solution algorithms. But for a problem of this complexity you may want to use NDSolveValue instead, with the usual changes. $\endgroup$
    – Bill
    Commented May 20, 2020 at 14:22
  • $\begingroup$ @Thanks Bill. Fully satisfied with your answer. $\endgroup$
    – vini
    Commented May 20, 2020 at 14:33
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    $\begingroup$ Your use of Conjugate could be replaced by Re: FullSimplify[Re[z] == ((z + Conjugate[z])/2)]. As Bill hints, I'd be surprised if DSolve has algorithms to solve ODEs that have Conjugate or Re in them, so you probably have to use numerical methods. $\endgroup$
    – Michael E2
    Commented May 20, 2020 at 15:01

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