Green's function expansion in a set of eigenfunction

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SUMMARY

The discussion focuses on decomposing the free space Green function, defined as G(𝑟; 𝑟′) = (e^(i k |𝑟 - 𝑟′|)) / (4 π |𝑟 - 𝑟′|), into a series of cylindrical mode eigenfunctions represented by Ψ(𝑟; k) = Hₘ(qr) sin(hz) e^(i m φ). The eigenfunctions form a complete set with discrete eigenvalues q and h, where h is defined as h = π / (2L). The user seeks guidance on expanding the Green function from a spherical representation to a waveguide context, referencing Jackson's "Electrodynamics" for potential methods.

PREREQUISITES
  • Understanding of Green's functions in quantum mechanics
  • Familiarity with cylindrical mode eigenfunctions and Hankel functions
  • Knowledge of waveguide theory and eigenvalue problems
  • Basic concepts of quantum dynamics, including Schrödinger and Heisenberg representations
NEXT STEPS
  • Study the decomposition of Green's functions in quantum mechanics
  • Explore the properties and applications of Hankel functions in waveguides
  • Review Jackson's "Electrodynamics," particularly chapters 2 and 3, for relevant methods
  • Investigate the interaction representation in quantum mechanics for further insights
USEFUL FOR

Physicists, quantum mechanics students, and researchers working on waveguide theory and Green's function applications in quantum dynamics.

kristobal hunta
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Hi! I encountered the problem that I need to decompose the Green function into a set of eigenfunction. Particularly, I have the free space Green function
[tex]G(\vec r; \vec r') = \frac {e^{i k | \vec r - \vec r'|} } {4 \pi | \vec r - \vec r'|}[/tex]
and I need to express it into series of cylindrical mode eigenfunctions
[tex]\Psi ( \vec r; k) = H_m ( q r) sin( h z) e^{i m \phi}[/tex]
[tex]k^2 = q^2 + h^2, h = \frac { \pi } {2 L}[/tex]

here H - Hankel's function of the first kind.
Eigenfunction forms a complete set, with discrete spectrum of eigenvalues q and h.
I know that we can decompose the Green function into set of eigenfunctions, but I have the Green function for spherical representation, and eigenfunctions are from waveguide formed by two infinite plates parallel to each other. I couldn't find anything relevant about expanding the Green function into arbitrary set of eigenfunctions. Would appreciate any opinion or advice on the matter :)
 
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Look in Jackson's Electrodynamics book, I believe that the solution can be found by applying either chapter 2 or 3's methods.
 
i want notes about quantum dynamics(Schrödinger,heisenberg and interaction representation or pictures of quantum mechanics)
 

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