Fourier transform of a differential equation

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SUMMARY

The discussion focuses on applying the spatial Fourier transform to the partial differential equation given by p_t = (a^2/2τ)p_{xx} + 2g(p + xp_x). The user correctly identifies the need to transform both sides of the equation, leading to the expression φ_t = - (a^2k^2/2τ)φ + 2g(φ + F(xp_x)). The transformation of the first term on the right-hand side is confirmed as - (a^2k^2/2τ)φ, while the last term, F(xp_x), remains a challenge. This highlights the complexities involved in handling differential equations with Fourier transforms.

PREREQUISITES
  • Understanding of partial differential equations (PDEs)
  • Knowledge of spatial Fourier transforms
  • Familiarity with the properties of Fourier transforms, specifically F(p_{xx}) = -k^2F(p)
  • Basic calculus, particularly differentiation with respect to time and space
NEXT STEPS
  • Study the application of Fourier transforms to partial differential equations
  • Learn about the properties and rules of Fourier transforms in detail
  • Research techniques for handling terms like F(xp_x) in Fourier transforms
  • Explore examples of solving PDEs using Fourier transform methods
USEFUL FOR

Students and researchers in applied mathematics, particularly those focusing on differential equations and Fourier analysis. This discussion is beneficial for anyone looking to deepen their understanding of transforming PDEs using Fourier techniques.

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Homework Statement


I'm supposed to take the "spatial Fourier transform" of the partial differential equation

[tex] p_t = \frac{a^2}{2\tau}p_{xx} + 2g(p + xp_x)[/tex]

for [itex]p = p(x,t)[/itex].

Homework Equations


Well, I guess I eventually need something like

[tex] \phi(k,t) = \mathbb F(p(x,t)) = \frac{1}{\sqrt{2\pi}} \int_{-\infty}^{\infty} p(x,t) e^{-ikx}\ dx.[/tex]

The Attempt at a Solution


I've never done anything like this before, so I'm really not sure what to do. I think if I get a few hints or a gentle nudge in the right direction, I'll be good to go, though.

I'm guessing that I should take the spatial Fourier transform [itex]\mathbb F[/itex] of both sides. So the LHS would become

[tex] \mathbb F(p_t) = \frac{1}{\sqrt{2 \pi}} \int \frac{\partial p}{\partial t}e^{-ikx}dx = \frac{1}{\sqrt{2 \pi}} \frac{\partial}{\partial t} \int p(x,t) e^{-ikx}dx = \phi_t.[/tex]

Is this right?
 
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And then I guess we can use the rule that

[tex] \mathbb F(p_{xx}) = -k^2 \mathbb F(p)[/tex]

to conclude that the transform of the first term on the RHS is just

[tex] -\frac{a^2k^2}{2\tau} \phi.[/tex]

So, at the end of the day, our differential equation becomes

[tex] \phi_t = -\frac{a^2k^2}{2\tau} \phi + 2g(\phi + \mathbb F(xp_x)).[/tex]

That last term on the right is giving me fits!
 

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