Is the Total Momentum in QED Actually Total Angular Momentum?

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Discussion Overview

The discussion centers around the relationship between total momentum and angular momentum in the context of Quantum Electrodynamics (QED). Participants explore whether the total momentum described in a text is indeed total angular momentum, particularly in light of dimensional analysis and the de Broglie relationship.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that the electrodynamic part has units of angular momentum, raising the question of whether it is valid to equate angular and linear momentum.
  • Another participant requests references for the claims made, emphasizing the need for derivations to support the discussion.
  • A third participant mentions that many texts refer to angular momentum simply as 'momentum', suggesting a potential source of confusion.
  • A later reply indicates agreement with the initial concern about the context of the question, implying that the specific text may not be necessary for the discussion.

Areas of Agreement / Disagreement

Participants express differing views on whether the total momentum in the text is indeed total angular momentum. There is no consensus on this issue, and the discussion remains unresolved.

Contextual Notes

Participants highlight the importance of references and derivations in understanding the claims made, indicating potential limitations in the discussion due to the lack of specific textual context.

AJ Bentley
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I was just reading a text on QED that equates the vector potential to electrodynamic momentum using the de Broglie relationship.
At a later stage, the current flow in a conductor is predicted by considering the total momentum of the charge in relation to the electrodynamic.
Everything works out and it all fits.

But when I look at the dimensions, I find that the electrodynamic part has the units of angular momentum. Whereas the total momentum is of course, well, I assume it's momentum.

Is this valid? can I simply add angular and linear momentum and equate that total to wavenumber.

Or is it that the total momentum being considered in the text is in actual fact the total angular momentum? Presumably the author felt it too obvious to mention?
 
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AJ Bentley said:
I was just reading a text on QED that equates the vector potential to electrodynamic momentum using the de Broglie relationship.

reference please.

But when I look at the dimensions, I find that the electrodynamic part has the units of angular momentum. Whereas the total momentum is of course, well, I assume it's momentum.

Is this valid?

reference please.

Or is it that the total momentum being considered in the text is in actual fact the total angular momentum? Presumably the author felt it too obvious to mention?

Reference please.

How can anyone have a clue how to answer you correctly, AJ, if you haven't given the derivation OR the reference??

...
 
Many texts refer to angular momentum simply as 'momentum'.
 
Thank you, that's what I thought.
(The actual context of the question isn't important Creator - there's no point anyone delving into the text)
 
Last edited:

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