Understanding Perturbation Theory and Spin in Quantum Mechanics

In summary, the individual is seeking clarification on whether the method used by Feynman in The Feynman Lectures on Physics Volume 3 is perturbation theory or something else. They have noticed similarities between the two methods but are not sure if they are the same. The response is that there are elements of perturbation theory in Feynman's method, but it is not a pure treatment. The individual finds this answer satisfying, unlike most people who would find it infuriating.
  • #1
1Kris
22
0
In my quest to learn quantum mechanics I've become a little confused and I have a question.
It is "In The Feynman Lectures on Physics Volume 3, is most of the work, eg. ammonia molecule done using perturbation theory or is this method something else, not perturbation theory?"
I started to learn a little about perturbation theory elsewhere, and it seemed similar but not quite the same, so I'm a little foggy about this.
 
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  • #2
1Kris said:
In my quest to learn quantum mechanics I've become a little confused and I have a question.
It is "In The Feynman Lectures on Physics Volume 3, is most of the work, eg. ammonia molecule done using perturbation theory or is this method something else, not perturbation theory?"
I started to learn a little about perturbation theory elsewhere, and it seemed similar but not quite the same, so I'm a little foggy about this.

I'm sorry, but I'm not sure what it is that you're asking?
 
  • #3
In the Feynman Lectures on Physics, Volume 3, Feynman uses a an approximation of treating systems as two state systems. Is this the same as perturbation theory, or is it a different method?
 
  • #4
1Kris said:
In the Feynman Lectures on Physics, Volume 3, Feynman uses a an approximation of treating systems as two state systems. Is this the same as perturbation theory, or is it a different method?

I think the best answer, infuriating as it may be, is "yes".
http://en.wikipedia.org/wiki/Perturbation_theory

You can see there are elements of it there, but it's not a pure treatment for the reasons you mention, I think.
 
  • #5
Haha thanks for that, why infuriating?
 
  • #6
1Kris said:
Haha thanks for that, why infuriating?

Generally people finding that the answer is "yes" to a yes or no question is infuriating. I'm glad you don't! :)
 

Related to Understanding Perturbation Theory and Spin in Quantum Mechanics

1. What is perturbation theory?

Perturbation theory is a mathematical method used to approximate solutions to problems that cannot be solved exactly. It involves breaking down a complex problem into a simpler one, where the solution is known, and then adding small corrections to the solution to get a more accurate result.

2. How does perturbation theory apply to spin?

In quantum mechanics, spin is a property of particles that can take on one of two values - either "up" or "down". Perturbation theory is used to calculate the effects of external forces on the spin of a particle, such as an applied magnetic field.

3. What is the role of perturbation theory in quantum mechanics?

Perturbation theory is an essential tool in quantum mechanics, as it allows us to solve problems that would otherwise be impossible to solve. It is used to calculate the energy levels and properties of particles in systems that cannot be solved exactly, such as atoms and molecules.

4. What is the difference between first-order and second-order perturbation theory?

First-order perturbation theory involves making small corrections to the solution of a problem using only the first term in a mathematical series. Second-order perturbation theory, on the other hand, involves using both the first and second terms in the series to make more accurate corrections to the solution.

5. Can perturbation theory be applied to systems with multiple particles?

Yes, perturbation theory can be applied to systems with multiple particles, such as molecules. In these cases, the perturbations are calculated for each individual particle and then combined to give an overall correction to the solution of the system.

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