Orbital angular momentum and powers of k

Click For Summary

Discussion Overview

The discussion revolves around the concept of orbital angular momentum in quantum mechanics, specifically the relationship between orbital angular momentum and powers of momentum (k) in the context of wave equations and scattering theory. Participants explore the theoretical underpinnings and seek references for further reading.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions the reason why orbital angular momentum greater than \(\ell=0\) leads to terms involving powers of momentum like \(k^\ell\).
  • Another participant requests clarification on the sources where this relationship is discussed, indicating a need for specific references.
  • A third participant cites Weinberg's "Lectures on Quantum Mechanics" as a source that discusses the requirement for states to be in S-wave to avoid suppression by factors \(k^\ell\).
  • Another contribution explains that this relationship arises from solving the radial part of the wave equation, mentioning the factor \(l(l+1)\) and the use of the variable \(\rho=kr\), leading to solutions that include terms of the form \(k^\ell\).
  • It is noted that the second part of the solution is rejected for finiteness near the origin, which contributes to the emergence of the \(k^\ell\) type term.
  • It is suggested that quantum mechanics textbooks covering scattering theory typically address this topic.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the initial question, as the discussion includes requests for clarification and references, indicating that multiple viewpoints and interpretations exist regarding the relationship between orbital angular momentum and momentum powers.

Contextual Notes

Limitations include the dependence on specific definitions and the context of the wave equation solutions, which may not be fully resolved in the discussion.

Einj
Messages
464
Reaction score
59
Hi guys,
I have a question which is probably stupid. I am studying angular momentum and I have found almost everywhere that, if we have orbital angular momentum higher than [itex]\ell=0[/itex] then it brings powers of the momentum of the system like [itex]k^\ell[/itex]. What is the reason of that? Can someone suggest a book where I can find it or something?

Thank you
 
Physics news on Phys.org
I may be able to help but I need to know where this is coming from. You say this appears in a few books, can you name one so I can check what it says?
 
You can find it, for example, in Weinberg - Lectures on Quantum Mechanics, in the chapter on Shallow Bound States, when he talks about the request for the state to be in S-wave in order to avoid suppression by factors [itex]k^\ell[/itex].
 
It comes out by solving the radial part of wave eqn which contains the factor of l(l+1),there we use
ρ=kr as the variable and in some simplification with potential,the solutions are of the form (ρl)+(1/ρl+1),second part is rejected for finiteness near the origin which does give kl type term.All quantum mechanics books containing scattering theory deals with it.
 
Ok, thank you very much. I'll definitely take a look at that!
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 28 ·
Replies
28
Views
6K
  • · Replies 3 ·
Replies
3
Views
2K