Quantum mechanics and expectation values.

In summary, the conversation discusses the calculation of expectation values in quantum mechanics. It is mentioned that when calculating <x>, if Ψ is odd then Ψ* will also be odd, resulting in <x> being odd. The same applies for when Ψ is even. However, the question is raised about the case when Ψ is neither odd nor even, using a Gaussian function as an example. In this case, <x> will not be equal to 0.
  • #1
Rabbot
2
0
I have a question about expectation values in quantum mechanics.

When calculating <x>=[itex]\int\Psi*x\Psi[/itex] does x always make this functions odd? If [itex]\Psi[/itex] is odd then [itex]\Psi*[/itex] I would assume is odd as well and then <x> would be odd*odd*odd, if [itex]\Psi[/itex] is even then I again assume it would be even*odd*even. Does an odd function make the whole function odd regardless?
 
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  • #2
In the two cases you mentioned, Ψ odd or Ψ even, like you say Ψ*Ψ will be even and you'll get <x>=0. However what if Ψ is neither odd nor even? If, for example, Ψ is a Gaussian centered at x = x0 then you'll get <x> = x0 ≠ 0.
 

1. What is quantum mechanics?

Quantum mechanics is a branch of physics that studies the behavior of particles at the atomic and subatomic level. It describes the fundamental laws that govern the behavior of these particles, which are often counterintuitive compared to classical physics.

2. What are expectation values in quantum mechanics?

In quantum mechanics, expectation values are the average values of physical quantities that can be measured on a system. They represent the most probable outcome of a measurement and are calculated using mathematical operators that represent the physical quantity.

3. How are expectation values calculated in quantum mechanics?

Expectation values are calculated using operators and the wave function of a system. The wave function represents the probability of finding a particle in a specific state, and the operators represent the physical quantity being measured. The expectation value is then obtained by taking the integral of the product of the wave function and the operator.

4. What is the significance of expectation values in quantum mechanics?

Expectation values play a crucial role in quantum mechanics as they provide a way to predict the most likely outcome of a measurement. They also help to understand the behavior of quantum systems and are used in calculating important physical quantities such as energy and momentum.

5. How does the uncertainty principle relate to expectation values in quantum mechanics?

The uncertainty principle in quantum mechanics states that it is impossible to know the exact values of certain pairs of physical quantities simultaneously. Expectation values play a role in this principle as they represent the most probable outcome of a measurement, but they do not provide complete information about the quantum system.

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