Why Do Fermion and Boson Operators Commute?

In summary, boson and fermion operators commute because they operate on different spaces - bosonic operators on the boson state space and fermionic operators on the fermion state space. This is due to the nature of their creation and annihilation operators, which raise and lower the number of particles in a specific orbital. This is also reflected in their combined state, where a boson and fermion state would be represented as a tensor product.
  • #1
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For bosons we define states as eg.

ln> = l1 0 1 ... >

where the numbers denote how many particles belong to the j'th orbital.

And similarly for fermions. We then define creation and anihillation operators which raise and lower the number of particles in the j'th orbital:

c_j, c_j^(dagger)

Now in many problems I have to commute bosons and fermion operators. I actually asked this question before, but I didn't completely understand the answer. My question is:
Why does fermion and boson operators commute? starting from the wavefunction symmetrization and antisymmetrization requirement
 
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  • #2
Is it possible that one only acts on bosons and one only acts on fermions so it doesn't matter which one you do first. (Just a guess as I know zero about this. But hey it's Friday night, why not look a bit silly!)
 
  • #3
It's been a while so I hope someone won't come along and tell me this is nonsense. But if I recall correctly, the reason is they live in different spaces. If you have a boson state ##|b\rangle## and a fermion state ##|f\rangle## then a combined state would be ##|b, f\rangle = |b\rangle \otimes |f\rangle##. A bosonic operator would look like ##\hat B \otimes 1## on this combined space, and a fermionic operator similarly like ##1 \otimes \hat F##.

Typing math on a smartphone is a bit of a pain, so I'll leave it at this, but hopefully you can work it out from there.
 

1. What is the difference between boson and fermion operators?

Boson and fermion operators are mathematical operators used in quantum mechanics to describe the behavior of particles. The main difference between them is that boson operators represent particles with integer spin, while fermion operators represent particles with half-integer spin.

2. How do boson and fermion operators affect the properties of particles?

Boson and fermion operators affect the properties of particles in different ways. For example, boson operators describe particles that can occupy the same quantum state, while fermion operators describe particles that cannot occupy the same state due to the Pauli exclusion principle.

3. Can boson and fermion operators be used to describe any type of particle?

Yes, boson and fermion operators can be used to describe both elementary particles (such as electrons and photons) and composite particles (such as atoms and nuclei).

4. How are boson and fermion operators related to creation and annihilation operators?

Boson and fermion operators are related to creation and annihilation operators, which are used to add or remove particles from a system. Boson operators are associated with creation operators, while fermion operators are associated with annihilation operators.

5. What are some real-world applications of boson and fermion operators?

Boson and fermion operators have many practical applications in fields such as condensed matter physics, quantum chemistry, and quantum information processing. They are also used in the study of superconductivity, superfluidity, and Bose-Einstein condensates.

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