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Jul 6, 2017 at 14:15 vote accept AccidentalFourierTransform
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Oct 21, 2015 at 23:48 answer added Void timeline score: 5
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Oct 17, 2015 at 16:26 history edited AccidentalFourierTransform CC BY-SA 3.0
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Oct 16, 2015 at 17:39 comment added Javier Here's something that might help. $\not{p}=m$ is impossible, at least in the usual representation of the gamma matrices. What happens is that if $p$ goes on shell (that is, $p^2=m^2$), $\not p -m$ doesn't have a matrix inverse. Also, remember that the propagators are functions of $p^\mu$; writing them as $S(\not p)$ is just a way of saying that $p^\mu$ only appears contracted with $\gamma^\mu$.
Oct 9, 2015 at 2:36 answer added user2309840 timeline score: 2
Oct 8, 2015 at 22:59 comment added gented $\not p = p^{\mu}\gamma_{\mu}$, where $\gamma_{\mu}$ are Clifford algebras operators, having one representation as Dirac matrices. However, a matrix (if you prefer) in the denominator means that you have to multiply the numerator by the inverse. Exploiting the contraction of the $\gamma$ matrices you will end up with something like $f(p)\cdot 1_{\textrm{Cliff}}$, where $f(p)$ has residues as complex function.
Oct 8, 2015 at 22:48 comment added AccidentalFourierTransform Im not sure what you are referring to as an operator... $\not p$ is a matrix, not an operator. The operators are $\psi$ and $\phi$, but the propagators are just c-numebers, $S(x-y)=\langle \Omega|T \psi^\alpha(x)\psi^\beta(y)|\Omega\rangle$. As these are expectation values of operators, I dont know where I am supposed to place the identity operator?
Oct 8, 2015 at 22:40 comment added gented Don't forget that any of the above expressions need to be multiplied by the identity operators in the respective spaces where they live. This said, you of course cannot bring $\not p$ in the denominator, that being an operator, unless you think of it as multiplication by $(\not p \pm m)^{-1}$; when so, multiplying by the other corresponding sign and contracting the Dirac matrices leaves back a function (whose residues do make sense) times the identity operator.
Oct 8, 2015 at 22:09 history asked AccidentalFourierTransform CC BY-SA 3.0