Is the Total Momentum in QED Actually Total Angular Momentum?

AJ Bentley
Messages
667
Reaction score
0
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?
 
Physics news on Phys.org
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:
Not an expert in QM. AFAIK, Schrödinger's equation is quite different from the classical wave equation. The former is an equation for the dynamics of the state of a (quantum?) system, the latter is an equation for the dynamics of a (classical) degree of freedom. As a matter of fact, Schrödinger's equation is first order in time derivatives, while the classical wave equation is second order. But, AFAIK, Schrödinger's equation is a wave equation; only its interpretation makes it non-classical...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
Is it possible, and fruitful, to use certain conceptual and technical tools from effective field theory (coarse-graining/integrating-out, power-counting, matching, RG) to think about the relationship between the fundamental (quantum) and the emergent (classical), both to account for the quasi-autonomy of the classical level and to quantify residual quantum corrections? By “emergent,” I mean the following: after integrating out fast/irrelevant quantum degrees of freedom (high-energy modes...

Similar threads

Replies
1
Views
2K
Replies
18
Views
3K
Replies
1
Views
2K
Replies
8
Views
2K
Replies
7
Views
2K
Replies
23
Views
2K
Back
Top