WE theorem to evaluate matrix elements

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SUMMARY

The discussion focuses on the application of the WE theorem for evaluating matrix elements in quantum mechanics, specifically involving total spin (F) and its projection (m) onto the z-axis. The user presents a formula for matrix elements, highlighting a concern regarding the correctness of the exponent in the term (-1)^(F'+m'-m). The user seeks clarification on the exponent while expressing confidence in the rest of the formula. Additionally, the discussion references the reduced matrix element <τ J ||T^{(k)}||τ' J'> as part of the evaluation process.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly angular momentum.
  • Familiarity with the WE theorem and its application in matrix element evaluations.
  • Knowledge of Clebsch-Gordan coefficients and six-j symbols.
  • Proficiency in manipulating mathematical expressions involving square roots and exponents.
NEXT STEPS
  • Review the derivation and applications of the WE theorem in quantum mechanics.
  • Study the properties and calculations of Clebsch-Gordan coefficients and six-j symbols.
  • Learn about the significance of reduced matrix elements in quantum transitions.
  • Investigate common pitfalls in matrix element evaluations and how to verify their correctness.
USEFUL FOR

Quantum physicists, researchers in theoretical physics, and students studying angular momentum in quantum mechanics will benefit from this discussion.

pollo
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Hi!

In my work I use the WE theorem to evaluate matrix elements. F being the total spin and m the projection onto the z-axis, I am using:

<JIFm|r_(-q)|J'IF'm'>=(-1)^(F'+m'-m)<Fm1q|F'm'>sqrt(2F+1)sixj(F, F', 1:J',J,I)<J'||r||J>

I have a problem with the (-1)^ part which I suspect to be wrong, but have not been able to find a formula to compare a check. Am quite sure the rest is right. Could somebody help and tell what should be in the exponent?
 
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pollo said:
hi!

In my work i use the we theorem to evaluate matrix elements. F being the total spin and m the projection onto the z-axis, i am using:

<jifm|r_(-q)|j'if'm'>=(-1)^{f'+m'-m}<fm1q|f'm'>\sqrt{2f+1}sixj(f, f', 1:j',j,i)<j'||r||j>

i have a problem with the (-1)^ part which i suspect to be wrong, but have not been able to find a formula to compare a check. Am quite sure the rest is right. Could somebody help and tell what should be in the exponent?

I have the theorem as:

[tex]<\tau J M|T_q^{(k)}|\tau' J' M'> = {1 \over {\sqrt{2J+1}}}<\tau J ||T^{(k)}||\tau' J'><J' k M' q| J M>[/tex]

where [tex]<\tau J ||T^{(k)}||\tau' J'>[/tex] is the reduced matrix element.

Unfortunately I couldn't make head nor tail of the function you're trying to use. Maybe I'll've been of some help. Either way, this has been here for a couple of days with no reply, so maybe this will help the discussion.
 

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