How to Calculate the Virial Theorem for a Particle Moving in a Potential?

Click For Summary

Homework Help Overview

The problem involves calculating the Virial Theorem for a particle moving in a potential defined by \(V(x) = kx^n\), where \(k\) is a constant and \(n\) is a positive even integer. The task requires showing relationships between the expected values of potential and kinetic energy in the context of quantum mechanics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster expresses confusion about how to calculate the expected values of potential and kinetic energy, specifically questioning whether it involves integrals or commutator techniques.
  • Some participants suggest starting with the Hamiltonian and exploring its components, prompting further inquiry into the definitions and calculations involved.

Discussion Status

The discussion is ongoing, with participants exploring different aspects of the problem. Some hints have been offered regarding the relationship between the Hamiltonian and its components, but no consensus or resolution has been reached yet.

Contextual Notes

The original poster notes difficulty in finding relevant information in their textbook, indicating a potential gap in resources or understanding of the topic.

Denver Dang
Messages
143
Reaction score
1

Homework Statement


A particle is moving along the x-axis in the potential:

\[V\left( x \right)=k{{x}^{n}},\]
where k is a constant, and n is a positive even integer. \left| \psi \right\rangle is described as a normed eigenfunction for the Hamiltonoperator with eigenvalue E.

Show through the "Virial Theorem" that:

\[\begin{align}<br /> &amp; \left\langle \psi \right|\hat{V}\left| \psi \right\rangle =\frac{2}{n+2}E \\ <br /> &amp; \left\langle \psi \right|\hat{T}\left| \psi \right\rangle =\frac{2}{n+2}E, <br /> \end{align}\]<br />
where \hat{V}\ and \hat{T}\ denotes the operators respectively for potential and kinetic energy.

Homework Equations


The Virial Theorem:

\[2\left\langle T \right\rangle =\left\langle x\frac{dV}{dx} \right\rangle \]

The Attempt at a Solution


Well, I'm kinda lost.
I'm not sure how to calculate anything tbh...

The thing that confuses me, which is what I think I should do, is calculating:

\[\begin{align}<br /> &amp; \left\langle \psi \right|\hat{V}\left| \psi \right\rangle \\ <br /> &amp; \left\langle \psi \right|\hat{T}\left| \psi \right\rangle \\ <br /> \end{align}\]<br />

But can't find anything in my book that shows how to calculate anything that looks like that.

So a hint would be very helpful :)Regards
 
Physics news on Phys.org
Start with

<br /> \left\langle \psi \right|\hat{H}\left| \psi \right\rangle = \left\langle \psi \right|\hat{T} + \hat{V} \left| \psi \right\rangle.<br />

What is the left side? What is the right side?
 
Sorry for the late reply...

But that is my problem. I'm not sure how to calculate that ?
Is it an integral, a commutator trick, or...? As I said, I can't seem to find anything in my book that shows how to calculate that.
 
Start at the beginning. What is

\left\langle \psi \right|\hat{H}\left| \psi \right\rangle?
 
Hint to George Jones' question:

\left| \psi \right\rangle is described as a normed eigenfunction for the Hamiltonoperator with eigenvalue E.
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
3K
Replies
16
Views
3K
Replies
3
Views
2K
Replies
2
Views
2K
  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
Replies
1
Views
2K
  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K