Differential equations with singularities

In summary, The conversation is about solving a system of coupled differential equations involving the variables f(r) and g(r), with the presence of a coupling parameter a. The speaker mentions that they have tried using Matlab but encountered issues with singularities. They are seeking help from advanced Matlab users and mention that they need the equations in a specific form for the ode45 function.
  • #1
kosmonautilus
2
0
I have to solve the following coupled differential equations

d^2f(r)/dr^2+1/r*df(r)/dr+(2-2*f(r)^2-2*a*g(r)^2-l_1^2/r^2)*f(r)=0

d^2g(r)/dr^2+1/r*dg(r)/dr+(2-2*g(r)^2-2*a*f(r)^2-l_2^2/r^2)*g(r)=0,

where a is the coupling. I think that it is not possible to solve it analytically (even in case a==0), so i have to do it numerically. I tried it with matlab, but bvp4c can not solve equations with singularities of second kind. Can somebody help me? (I'm a advanced user of matlab)
 
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  • #2
Thank you, but for ode45 I need the 4 equations in the form dydx=... To obtain this, I have to divide by r^2 again and I have the same problem with the singularities
dy(1)=y(2)
r^2*dy(2)= r*y(2)+...
 

FAQ: Differential equations with singularities

What are singularities in differential equations?

Singularities in differential equations refer to points or values where the equation becomes undefined or has an infinite value. These points can occur due to division by zero, taking the logarithm of zero, or in cases where the solution becomes unbounded.

How do singularities affect the solution of a differential equation?

Singularities can significantly alter the behavior of the solution to a differential equation. In some cases, they can cause the solution to become discontinuous or have a singularity itself. They can also lead to multiple solutions or the non-existence of a solution.

What are the different types of singularities in differential equations?

There are three main types of singularities in differential equations: removable, essential, and irregular. Removable singularities can be removed by redefining the function at that point. Essential singularities cannot be removed and can lead to an infinite number of solutions. Irregular singularities are points where the solution is not analytic and cannot be expressed using a power series.

How are singularities classified in differential equations?

Singularities are classified based on their behavior and impact on the solution. They can be classified as isolated or non-isolated, essential or non-essential, and regular or irregular. Isolated singularities occur at distinct points, while non-isolated ones can form a continuous curve. Essential singularities are non-removable, while non-essential ones can be removed. Regular singularities have a finite value, while irregular ones have an infinite value.

How do you deal with singularities in differential equations?

Dealing with singularities in differential equations can be challenging and often requires specialized techniques. One approach is to transform the equation into a new form that is free of singularities. Another method is to use numerical methods to approximate the solution. In some cases, it may also be possible to use series solutions or special functions to handle the singularity. Ultimately, the best approach will depend on the specific type and behavior of the singularity.

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