Timeline for What's wrong with this QFT thought experiment?
Current License: CC BY-SA 3.0
17 events
| when toggle format | what | by | license | comment | |
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| Jul 29, 2013 at 13:26 | comment | added | Jia Yiyang | @MichaelBrown:I'm still feeling a bit vague about Coleman's arguments. He used a shrinking box thought experiment and mathematical properties of $\langle x|y\rangle$ to show that a single-particle theory must be inconsistent, so far so good. Then he turned to microcausality condition $[O(x),O(y)]=0$, of course this is no problem if we strictly adhere to QM axioms and say Hermitian operators are all we can discuss when it comes to measurement. However a direct attack to the shrinking box experiment is lacking, it seems the interaction between the box and the particle has to be considered | |
| S Jul 17, 2013 at 5:15 | history | bounty ended | CommunityBot | ||
| S Jul 17, 2013 at 5:15 | history | notice removed | CommunityBot | ||
| Jul 11, 2013 at 15:12 | comment | added | twistor59 | @MichaelBrown +1 for the Sid Coleman reference: "Admittedly, the chance that the particle is found outside the forward light cone falls off exponentially as you get further from the light cone, and that makes it extremely unlikely that I could go back and convince my mother to have an abortion" | |
| Jul 11, 2013 at 8:56 | answer | added | Trimok | timeline score: 1 | |
| Jul 9, 2013 at 6:12 | answer | added | Neuneck | timeline score: 2 | |
| Jul 9, 2013 at 4:48 | comment | added | Raskolnikov | How does Bob encode information in the particles? | |
| Jul 9, 2013 at 3:39 | comment | added | Michael | This is discuss in some detail in Sidney Coleman's QFT lecture notes. See my answer to an old question which is a near duplicate of this one! You explicitly define the fields to commute outside the lightcone, so any observable constructed from fields must commute outside the lightcone. | |
| S Jul 9, 2013 at 3:19 | history | bounty started | hwlin | ||
| S Jul 9, 2013 at 3:19 | history | notice added | hwlin | Draw attention | |
| Jun 5, 2013 at 4:45 | comment | added | hwlin | Yes, but he later says that the difference between particles and "disturbances in the field" is a semantic one. "Experimentalists choose to call this disturbance in the field a particle of mass $m$." | |
| Jun 4, 2013 at 19:05 | comment | added | twistor59 | Actually the statement by Zee is that "a quantum field can leak out", not that a particle can leak out | |
| Jun 4, 2013 at 13:00 | comment | added | Jim | Also, in QFT this isn't the final propagator. This problem is fixed by using the Feynman-Green function or the retarded Green function, which is $\Theta(x_0-y_0)(D(x-y)-D(y-x))$ which is 0 for $(x-y)^2<0$ (space-like separation) | |
| Jun 4, 2013 at 11:07 | history | tweeted | twitter.com/#!/StackPhysics/status/341873919067815936 | ||
| Jun 4, 2013 at 10:34 | comment | added | Trimok | Propagators do not represent real particles. They represent perturbations of fields. | |
| Jun 4, 2013 at 9:38 | history | edited | Qmechanic♦ |
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| Jun 4, 2013 at 9:21 | history | asked | hwlin | CC BY-SA 3.0 |