not linear homogeneus differential equation system... too complicated for mathmeatica... maybe only for me! :)
- To: mathgroup at smc.vnet.net
- Subject: [mg41718] not linear homogeneus differential equation system... too complicated for mathmeatica... maybe only for me! :)
- From: "Alessandro" <TheOpps75 at yahoo.it>
- Date: Mon, 2 Jun 2003 04:35:24 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
For the type of system I'm studing I guess the system of differential
equation (not liear) I'm going to asking about should have solution.
Unfortunatly my knoledge about mathmatica is very poor, seems to be a bit
too complicated to try with paper and pencil in a reasoneble time, and so
I'd like to have some help.
The Mathematica cell is:
DSolve[
{ s'[t] == -A*s[t] +B*u[t],
u'[t] == A*s[t] - (E + C*a[t] + B)*u[t],
a'[t] == F*b[t] - C*a[t]*u[t],
b'[t] == C*a[t]*u[t] - (G + F)*b[t],
s[0] == s0, a[0] == a0, b[0] == 0, u[0] == 0},
{s[t], u[t], a[t], b[t]}, t]
I have two problem:
1) Before I was considering C=C' 1/a[t]... the system was linear and
solvable. Nevertheless the solution was a very long formula. I needed to
compact the result with FullSimplify. Is it the right way or I can feed
DSolve with some option in order to get a compact result by default?
2) Later I realized I was solving the erroneous equations. This new non
linear system is solved by Mathematica, after some minutes (CPU 2GHz 512Mb),
Mathematica answer with the same input I gave as output... well... I think
it is not able to solve it. There is some mathematica toolbox or some way to
solve it. It is probable I wiil need to change other things in the equation
so I'd prefer some suggestion in order to understand what to do instead of
the raw solution... however I will not disregard a solution :))))
Wow... too long... for a question probable will not interess too much
people... sorry
Thanks
Ale