Zwiebach 210 Hmwk: Commutator not Equal 0

  • Thread starter ehrenfest
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In summary, a commutator is an operator in quantum mechanics that represents the difference between a particle's position and momentum. It is not equal to 0 in Zwiebach 210 Hmwk because of the uncertainty in both the position and momentum of a particle. This uncertainty is related to the Heisenberg uncertainty principle, which states that the more precisely we know one property of a particle, the less precisely we can know another. The commutator can never be equal to 0 in quantum mechanics, and it plays a crucial role in determining the uncertainty in the measurement of physical quantities. This shows that there is a fundamental limit to how precisely we can know certain properties of a particle at the same time.
  • #1
ehrenfest
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Homework Statement


Zwiebach claims that differentiating 12.12, which is

[tex]X^I (\tau, \sigma) X^J(\tau, \sigma')-X^J(\tau, \sigma') X^I(\tau, \sigma) = 0[/tex]

w.r.t. tau gives the same commutator with everything dotted. I think that is downright wrong. If you use the product rule to write everything out, it just doesn't work out.


Homework Equations


The Attempt at a Solution

 
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  • #2
Apply equation (12.21) to the second equation in the first line of equations (12.12).
 
  • #3
You also have to use 12.1 to get the leftmost part, don't you?
 

What is a commutator?

A commutator is an operator in quantum mechanics that represents the difference between a particle's position and momentum.

Why is the commutator not equal to 0 in Zwiebach 210 Hmwk?

The commutator is not equal to 0 because there is a non-zero uncertainty in both the position and momentum of a particle, meaning they cannot be measured simultaneously with perfect precision.

How is the commutator related to the Heisenberg uncertainty principle?

The commutator is a fundamental concept in the Heisenberg uncertainty principle, which states that the more precisely we know a particle's position, the less precisely we can know its momentum, and vice versa.

Can the commutator ever be equal to 0?

No, the commutator can never be equal to 0 in quantum mechanics. This is a fundamental principle of the uncertainty principle and the probabilistic nature of quantum systems.

How does the commutator affect the measurement of physical quantities in quantum mechanics?

The commutator plays a crucial role in determining the uncertainty in the measurement of physical quantities in quantum mechanics. It shows that there is a fundamental limit to how precisely we can know certain properties of a particle at the same time.

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