Question: Lotka-Volterra system

  • Thread starter Thread starter mathboy20
  • Start date Start date
  • Tags Tags
    System
mathboy20
Messages
27
Reaction score
0
Hi

I need help intepreting the following.

Given Lotka-Volterra model system

\begin{array}{cc} x'_1 = (a-bx_2)x_1 \\ x'_2 = (cx_1 -d) x_2\end{array}

Look at the system on the open 1.Quadrant K; where a,b,c,d are all positive constants.

Show that the system is integratable, which supposedly implies that there exist a C^1-function F:U \rightarrow \mathbb{R} where U \subseteq K is open, and close in K.

According to my professor "close" implies that for every point in K, there exist a sequence of socalled "limitpoints", who's elements belongs to K. Also as a consequence of "close" \nabla F \neq 0 for all x \in U, and F is constant on all trajectories of the system.

What is my first step here? Do I prove that there exist a solution for the system only in K?

Sincerley Yours
Mathboy20
 
Last edited:
Physics news on Phys.org
Volterra

To begin with you need to find a function of two variables (x_1, x_2) which is a constant of motion. i.e. its time derivative is zero. Then you worry where it is defined.
 
You might also want to look up the definition of "integrable" since that is what you are asked to show!
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

Similar threads

Replies
2
Views
3K
Replies
8
Views
2K
3
Replies
100
Views
11K
Replies
4
Views
3K
2
Replies
67
Views
11K
Replies
46
Views
8K
Replies
2
Views
7K
Back
Top