[A,B] = AB-BA, so the commutator should be a matrix in general, but yet(adsbygoogle = window.adsbygoogle || []).push({});

[x,p]=i*hbar...which is just a scalar. Unless by this commutator, we mean i*hbar*(identity matrix) ?

I am asking because I see in a paper the following:

tr[A,B]

Which I interpret to mean the trace of the commutator [A,B]. But if [A,B] is just a scalar, then trace of a scalar should always just be the scalar..

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# Is a commutator a scalar?

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