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Results tagged with operators
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user 29955
In physics, an operator is almost always either a square matrix or a linear mapping between two function spaces (defined on, say, $\mathbb R^n$). Operators serve as observables and as time evolution operators in Quantum Mechanics. This tag will most often find valid use in quantum mechanics; don't use this tag just because your equations contain "everyday operations" like $\times$, $+$!
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Proof for a time-ordering equation in Negele & Orland (1998)
Let $T$ be the time-ordering operator which orders operators $A_1(t_1), A_2(t_2), \ldots$ such that the time parameter decreases from left to right:
$$T[A_1(t_1) A_2(t_2)] = A_2(t_2) A_1(t_1) \text{ …
3
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Proof for a time-ordering equation in Negele & Orland (1998)
I think the argument also works for more operators, but it will become more opaque and cumbersome to write it in an online forum. …