Analyzing Nonlinear PDE Systems with Polar Coordinates

In summary, the conversation discusses a system of two ordinary differential equations and the attempt at solving it using polar coordinates. The equations in polar coordinates are shown and the idea of using variation of parameters is mentioned. The conversation also touches on the topic of qualitative analysis and finding stationary points. The possibility of solving the differential equations is also mentioned.
  • #1
menphis
2
0

Homework Statement


Hi, i have the following system of equation. In the task is that system have periodic solution and have to be used polar coordinates.

Homework Equations


x'=1+y-x^2-y^2
y'=1-x-x^2-y^2

The Attempt at a Solution


After transfer to polar system i tried to use the method of variation of parameters, but without success.
 
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  • #2
1) Why is this posted in the "preCalculus" section?
I assume that was a mistake and I will move it to "Calculus and Beyond" homework.

2) Why is this tltled "PDE"? I see no partial differential equations. I see a system of two ordinary differential equations.

Changing to polar coordinates looks like a very good idea but I don't know what you mean by "variation of parameters" for a non-linear equation. What equations did you get after changing to polar coordinates?
 
  • #3


I'm sorry for PDE and wrong section
In the polar coordinates have equations this shape:

rho' cos(phi)=rho sin(phi)(1+phi')
rho' sin(phi)=- rho cos(phi)(1+phi')
 
  • #4
Did you get anywhere yet?
One thing you might notice straightaway is that any point on the circle x2 + y2 - 1 = 0 you find the equations become those of SHM whose solution is that same circle, so that circle is a solution.
However it is not SHM in general, for no other points have that property and (0, 0) is not a stationary point.

Do you know how to analyse such systems qualitatively? This one appears quite complex and surprising.
Main thing, you have to find the stationary points (i.e. where x' = y' = 0) and analyse the stability of the linear approximation around them.

Perhaps the d.e. s can be solved too, I don't know yet.
 
Last edited:

Related to Analyzing Nonlinear PDE Systems with Polar Coordinates

1. What is a system of nonlinear PDE?

A system of nonlinear PDE (partial differential equations) is a set of equations that involves multiple dependent variables and their partial derivatives with respect to multiple independent variables. Unlike linear PDEs, which have a linear relationship between the dependent and independent variables, nonlinear PDEs have nonlinear relationships and are much more difficult to solve analytically.

2. What are some applications of systems of nonlinear PDEs?

Systems of nonlinear PDEs have a wide range of applications in various fields of science and engineering, such as fluid dynamics, electromagnetism, quantum mechanics, and population dynamics. They are often used to model complex systems, such as weather patterns, chemical reactions, and biological processes.

3. How are systems of nonlinear PDEs solved?

There is no general method for solving systems of nonlinear PDEs, and different techniques must be applied depending on the specific equations and boundary conditions. Some common methods include separation of variables, finite difference methods, numerical approximations, and perturbation methods.

4. What are some challenges in solving systems of nonlinear PDEs?

Systems of nonlinear PDEs can be extremely difficult to solve due to their complexity and the lack of general methods. They often require advanced mathematical techniques and computational methods, and may also have multiple solutions or no exact solution at all.

5. How are systems of nonlinear PDEs used in research and technology?

Systems of nonlinear PDEs are used in a wide range of research fields, including mathematical physics, engineering, and computer science. They are also essential in the development of new technologies, such as weather forecasting, drug design, and computer graphics. By accurately modeling and simulating complex systems, they can help scientists and engineers better understand and predict real-world phenomena.

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