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Category Archives: Green’s functions

Green’s function for diffusion in 1D. Part 2.

I finalize the discussion started in Part 1 with an example showing the behavior for a specific source, which is a simple Gaussian in space and in time. I comment on how to make sure the desired initial conditions are satisfied by adding a solution to the homogeneous equation. Video. Notes.

Posted byjoaquindrutJanuary 3, 2023January 3, 2023Posted inComplex numbers, Fourier series and transforms, Green's functions

Green’s function for diffusion in 1D. Part 1.

I solve for the Green’s function of the diffusion operator on the whole real line. To that end, I use Fourier transforms in space and time and contour integration (more on that later!).Video. Notes.

Posted byjoaquindrutJanuary 1, 2023January 1, 2023Posted inComplex numbers, Fourier series and transforms, Green's functions

Green’s functions of the Laplacian: eigenfunction expansion.

Using the cartesian and spherical eigenfunctions of the Laplacian discussed in previous videos, we build the corresponding Green’s functions. What happens when we remove the boundaries? A step toward Fourier transforms and quantum field theory.Video. Notes.

Posted byjoaquindrutDecember 21, 2022December 21, 2022Posted inFourier series and transforms, Green's functions

A 1d Green’s function example two ways

A closer look at how to calculate a Green’s function in a 1D example, using a direct solution and a spectral representation. Video. Notes.

Posted byjoaquindrutNovember 28, 2022November 28, 2022Posted inGreen's functions, Linear algebra, Other fun stuff

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