Mathematical misconception in scattering: switching from cartesian to spherical

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Discussion Overview

The discussion revolves around the mathematical transition from Cartesian to spherical coordinates in the context of nucleon-nucleon interactions, specifically focusing on the representation of wave functions. Participants explore the implications of this transition and the appearance of specific terms in the equations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant notes that the incident wave in Cartesian coordinates is represented as ψ= Ae^{ikz} and questions the origin of the '2ik' in the denominator when transitioning to spherical coordinates.
  • Another participant points out a difference in representation, suggesting that writing e(ikr) - e(-ikr) leads to a form involving sin(kr)/kr, which they argue differs from the Cartesian representation e(ikz)=e(ikr cosθ).
  • A third participant reiterates the transition from the plane wave to spherical waves, confirming the form ψ=\frac{A}{2ik}( e^{ikr}/r - e^{-ikr}/r) as noted in a nuclear course.
  • A fourth participant introduces a series expansion involving spherical Bessel functions and Legendre polynomials, suggesting that this form can be derived from spherical Hankel functions, specifically for l=0.

Areas of Agreement / Disagreement

Participants express differing interpretations of the mathematical transition and the implications of specific terms, indicating that multiple competing views remain without a clear consensus.

Contextual Notes

The discussion includes assumptions about the mathematical properties of wave functions and the definitions of spherical Bessel functions and Hankel functions, which are not fully resolved.

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If we were to consider a nucleon-nucleon interaction:
We know that the incident wave (plane wave) is ψ= Ae[itex]^{ikz}[/itex], propagating in z direction

But for some mathematical facilities, we tend to use spherical coordinates, the wave becomes = [itex]\frac{A}{2ik}[/itex][e[itex]^{ikr}[/itex]/r - e[itex]^{-ikr}[/itex]/r]

How come?
Where did the '2ik' in the denominator come from?
 
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where you have seen that.
writing e(ikr) - e(-ikr)=2i sin(kr),we have second one as
sin(kr)/kr which is different from e(ikz)=e(ikr cosθ)
 
What? Sorry, but I didn't get where you're pointing to.
What was written is as follows:

The incident plane wave traveling in z direction:
ψ=Ae[itex]^{ikz}[/itex]

They then mentioned that it was mathematically easier to work with spherical waves e[itex]^{ikr}[/itex]/r and e[itex]^{-ikr}[/itex]/r.

Lastly, for l=0,
ψ=[itex]\frac{A}{2ik}[/itex]( e[itex]^{ikr}[/itex]/r - e[itex]^{-ikr}[/itex]/r)

That was what's written in some nuclear course.
 
e(ikz)lil(2l+1)jl(kr)pl(cosθ)
lil(2l+1)(i/2k)[e-i(kr-l∏/2)/r-ei(kr-l∏/2)/r] pl(cosθ)
jl(kr) is spherical bessel function and Pl you know.this form of spherical bessel can be gotten from spherical hankel functions of first and second kind(their addition).for l=o this reduces to the required form.
 

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