Numerical solution for an integral equation?

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Discussion Overview

The discussion centers around a specific integral equation that the original poster seeks to solve numerically. The equation involves a second derivative of a function F(t) and an integral that includes a sine function and a power of the difference between two parameters, t and t'. The participants explore the nature of the equation, its notation, and potential numerical methods for solving it.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • The original poster presents an integral equation and requests help in identifying its category and numerical solution methods.
  • One participant questions the notation used in the integral, seeking clarification on the limits and the meaning of the t' variable.
  • Another participant suggests that the integral is indefinite but implies practical limits from 0 to infinity.
  • There is confusion regarding the notation, particularly whether t' represents a derivative or a separate variable.
  • A suggestion is made to consider using Laplace transforms to eliminate the second derivative and to explore Gaussian quadrature for numerical integration.
  • Recommendations are provided to consult resources like _Numerical Recipes in C_ for methods related to numerical solutions of differential equations.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the notation and limits of the integral. There is no consensus on the best approach to solve the equation, and multiple suggestions for methods are presented without agreement on a single solution.

Contextual Notes

There are unresolved questions about the notation and limits of the integral, as well as the implications of the parameters involved. The discussion reflects uncertainty about how to proceed with the numerical evaluation of the function F(t).

Asban
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Hello,

I have been encountered an integral equation that I need to solve\evaluate numericly and I didn't find anything like it in my search yet.

The equation:

\frac{d^2 F(t)}{dt^2}=const*\int_{t'}\frac{sin(F(t)-F(t'))}{(t-t')^{2k}}dt'

If it helps there is a specific case, when K=1 there is an analitical solution: F(t)=2arctan(\frac{t}{t_0}).

For now, two mainly things will help me:

1: What is the exact name of category of this integral equation?
2: What is the name of the numerical solution that solve it, or solve something similar to this equation and where should I start looking?

Thank you
Ofek
 
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Asban said:
Hello,

I have been encountered an integral equation that I need to solve\evaluate numericly and I didn't find anything like it in my search yet.

The equation:

$$\frac{d^2 F(t)}{dt^2}=const*\int_{t'}\frac{sin(F(t)-F(t'))}{(t-t')^{2k}}dt'$$
I don't understand your notation for the integral...?
 
If I understant your question, the range is from 0 to infinity for all practical purposes but in general is suppose to be indefinite integral.
 
Asban said:
If I understant your question, the range is from 0 to infinity for all practical purposes but in general is suppose to be indefinite integral.
Is there a reason you put the t-prime on the bottom part of the integral, then? :confused:

Also, does your t-prime imply the derivative of t, or is that a separate variable? Your notation is confusing.
 
t and t' are different parameters, so as you see in the right hand side t acts as a constant in the integral,
but still in the right hand side there is a 2nd derivative of F with respect to the parameter t.

I need to evaluate numericly the function F(t) that solve this equation.
 
If you were to sort out what that integral means, you might have some better luck. You can't do an integral numerically unless it has specific limits. So what you mean by putting the t' by the integral sign has to be made clear.

After that, round up the usual suspects. Look at things like a Laplace transform to try to get rid of the 2nd derivative. Look at taking some derivative of the entire equation to convert it to a differential equation without any integrals. Look at things like Gaussian quadrature to convert the integral to a set of valuations of F(t) with appropriate coefficients. Look up ways to numerically solve differential equations. You could start with a book like _Numerical Recipes in C_ (or Fortran if you prefer) for introductory methods.
Dan
 

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