4 coupled ode

  • Thread starter Qyzren
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  • #1
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Hi guys, i have 4-coupled ode's that are giving trouble

[tex](1) \frac{dy_1}{dt}=y_2y_3-\mu y_1, \hspace{1cm} \\(2) \frac{dy_2}{dt}=y_1y_4-\mu y_2, \hspace{1cm} \\(3) \frac{dy_3}{dt}=1-y_1y_2, \hspace{1cm} \\(4) \frac{dy_4}{dt}=1-y_1y_2[/tex]
I need to show that the steady state solutions are
[tex]y_1=\pm k, y_2=\pm k^{-1}, y_3=\mu k^2, y_4 = \mu k^{-1}[/tex] where [tex]\mu (k^2-k^{-2})=A[/tex] a const.
now in an earlier part of the question, I was able to show that [tex]y_3-y_4=A[/tex].
But trying to solve these coupled ODE's is giving trouble. I tried solving this in mathematica using DSolve as well, and mathematica doesn't seem to know how to do it either.

mathematica code:
[tex]\text{DSolve}\left[\left\{\text{y1}'[t]==-\mu \text{y1}[t]+\text{y2}[t] \text{y3}[t],\text{y2}'[t]==-\mu \text{y2}[t]+\text{y1}[t] \text{y4}[t],\text{y3}'[t]==1-\text{y1}[t] \text{y2}[t],\text{y4}'[t]==1-\text{y1}[t] \text{y2}[t]\right\},\{\text{y1}[t],\text{y2}[t],\text{y3}[t],\text{y4}[t]\},t\right][/tex]

PS: how do i get each of the differential equations on a new line? \\ and \newline didn't work.
each of the ODE's starting with the derivative should be on a new line
 
Last edited:

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
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You don't have to solve the ODE's to find steady state solutions, do you? Just put all of the derivatives equal to zero. Now it's just an algebra problem.
 
  • #3
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thanks, problem solved
 

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