Where did I miss a minus sign?

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In summary, the conversation is about finding a missing minus sign and showing that the last term is equal to 1. The solution involves expanding the exponentials and considering the action on the ground state with powers of a† and a.
  • #1
davon806
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Homework Statement


a.jpg


Homework Equations

The Attempt at a Solution


e.jpg


1.1st circle on the left : where did I miss a minus sign?
2. How to show that the last term is equal to 1?

Thanks!
 
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  • #2
davon806 said:
1.1st circle on the left : where did I miss a minus sign?
I don't think you missed a minus sign here.
How to show that the last term is equal to 1?
You'll have to see if it is, in fact, equal to 1.

You could try expanding the two exponentials in your question-mark expression and see if you can simplify it. Think about what happens when you act on the ground state with powers of a followed by powers of a.
 
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  • #3
TSny said:
I don't think you missed a minus sign here.
You'll have to see if it is, in fact, equal to 1.

You could try expanding the two exponentials in your question-mark expression and see if you can simplify it. Think about what happens when you act on the ground state with powers of a followed by powers of a.

Thanks, after expanding the exponential I recover the minus sign:smile:.
 
  • #4
OK, good.
 

FAQ: Where did I miss a minus sign?

What are raising and lowering operators?

Raising and lowering operators are mathematical operators used in quantum mechanics to raise or lower the energy state of a quantum system. They are represented by symbols such as a^+ and a^-, and are used to manipulate wavefunctions and calculate energy levels.

How do raising and lowering operators work?

Raising and lowering operators work by acting on a wavefunction to change its energy state. The raising operator (a^+) increases the energy state by one unit, while the lowering operator (a^-) decreases the energy state by one unit. These operators can be applied multiple times to change the energy state of a system.

What is the significance of raising and lowering operators in quantum mechanics?

Raising and lowering operators are essential tools in quantum mechanics as they allow for the calculation of energy levels and transitions between energy states. They also play a crucial role in the Heisenberg uncertainty principle and the commutation relations between observables.

Are raising and lowering operators the same as ladder operators?

Yes, raising and lowering operators are also known as ladder operators because they "ladder" a wavefunction up or down in energy states. The term "ladder operators" is often used in the context of angular momentum and spin in quantum mechanics.

Can raising and lowering operators be used in other fields of science?

While raising and lowering operators are primarily used in quantum mechanics, they have also found applications in other fields such as statistical mechanics and optics. They are useful in the calculation of thermal averages and can be used to describe the behavior of photons in a laser, for example.

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