# Normal ordering for bosons vs fermions

planetology
Why is it that when normal ordering the terms in the Hamiltonian for bosons, the commutation rules are ignored, but when normal ordering fermion operators the anti-commutation rules are used to justify a change in sign?

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Gold Member
I remember thinking about this a few years ago, and I seem to remember the answer was in the fact that the negative sign canceled with another negative sign, giving the appearance that we ignore the rule.

Here is an easy-to-read document that will be of some assistance:

http://xxx.lanl.gov/pdf/physics/0212061

I will get back to this later with a more definitive post.

planetology
Originally posted by Tom

Here is an easy-to-read document that will be of some assistance:

http://xxx.lanl.gov/pdf/physics/0212061

I will get back to this later with a more definitive post.

Thanks, that paper is a really good one. I have not gotten all the way through it yet so don't know if it answers the main question, but very useful in any case.

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