Timeline for Why doesn't superselection forbid almost every superposition?
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 6, 2019 at 19:58 | comment | added | Sachin Valera | @Arnold Neumaier But roughly speaking, doesn't the standard model 'correspond' to $U(1)\times SU(2)\times SU(3)$, with $U(1)$ precisely describing the QED gauge theory (symmetry group for EM-interaction) ? So Zhengyan's analogy holds: the Galilean group was replaced by the Poincare group... what if the U(1) symmetry group is revised in some future theory (i.e. what if the standard model is revised). This is my understanding of his last few paragraphs. | |
| Apr 1, 2018 at 19:43 | comment | added | Arnold Neumaier | As mentioned in my answer, the term superselection sector is a precise technical term. For the case of charge, superselection is a general property of gauge theories, see Strocchi, F., & Wightman, A. S. (1974). Proof of the charge superselection rule in local relativistic quantum field theory. Journal of Mathematical Physics, 15(12), 2198-2224. This has nothing to do with the standard model, as electrical charge is intrinsically linked to QED, which is a gauge theory. In particular, your last paragraph is void of meaning. | |
| Apr 1, 2018 at 18:45 | comment | added | Zhengyan Shi | @ArnoldNeumaier I agree with you that the statement about "beliefs" is trivial and I should probably delete it. Perhaps the more meaningful statement (meaningful to me but you can definitely disagree) appears in the last paragraph, that the criterion for deciding what we call "superselection" rests on a sense of universality, which distinguishes electric charge from examples that confuse the OP in the question statement. Clearing that confusion with some precise definitions and examples was the main objective of this answer. | |
| Apr 1, 2018 at 16:51 | comment | added | Arnold Neumaier | All physics, like superselection rules, captures beliefs we have about the nature of possible physical observables in the universe, limited by current experimental probes and theoretical models. | |
| Apr 1, 2018 at 12:19 | comment | added | Arnold Neumaier | This is a valid answer only in as far all of physics is a matter of contemporary belief, and then it is a trivial statement. | |
| Mar 31, 2018 at 0:12 | comment | added | Emilio Pisanty | This is an outstanding answer and it's worthy of a rather bigger one than the current run. For now, though, +1. | |
| Mar 30, 2018 at 17:40 | history | answered | Zhengyan Shi | CC BY-SA 3.0 |