Timeline for How could quantum effects occur in the early universe without an observer?
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12 events
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| Aug 29, 2020 at 2:03 | comment | added | DanielSank | "If you don't use the Copenhagen interpretation, quantum mechanics still works fine." No, it does not. The unitary part of quantum mechanics tells you how to calculate $\left \lvert \Psi(t) \right \rangle$, but then what? Shouldn't a theory of Nature tell how to predict the outcome of an experiment? How do you do that without Copenhagen or something similar? | |
| Oct 8, 2019 at 22:28 | comment | added | user76284 | @AliLavasani "In many worlds, you have the problem that you cannot interpret probability for your worlds" Are you asking how you get the Born rule? That's an excellent question. Most "interpretations" don't even try to answer it. If MWI can, that's a huge achievement. See Many Worlds, the Born Rule, and Self-Locating Uncertainty by Carroll and Sebens for an example. | |
| Jan 11, 2019 at 21:30 | comment | added | jinawee | Regarding the symmetry point, I think OP's question is: we observe CMB temperature anisotropies->these are due to early-universe field quantum fluctuations->these fluctuations are due to measurements, since the quantum state is symmetrical. | |
| Jan 11, 2019 at 17:28 | comment | added | John Dvorak | @AliLavasani you have just one universe, it's just in a superposition of all possible states. They can't properly be called universes because the set of possible states in a superposition depends on what you are trying to measure about the quantum state, and classical states only exist as a limit for a large ensemble of particles | |
| Jan 11, 2019 at 15:33 | comment | added | Alex L | @John In many worlds, you have the problem that you cannot interpret probability for your "worlds". For example, suppose the probability of quantum event A is 0.7, and the probability of quantum event B is 0.3. What does this mean? Does it mean you have 7 universes in which A happens and 3 ones in which B happens, or what? | |
| Jan 11, 2019 at 15:14 | comment | added | John Dvorak | @AliLavasani how about the good old many-worlds interpretation? No wavefunction collapse, no issue choosing when it happens. The only thing that you lose is the notion that only the universe that you see is what exists. It's not that far-fetched either. An electron created by the collision of two gamma photons can only "see" a positron that flies away in the exact opposite direction, which is just a layman's way of saying that a superposition of states evolves the same as if you evolve each state separately and only then sum up the states. | |
| Jan 11, 2019 at 1:46 | comment | added | Alex L | @Wolphram Notice that Copenhagen perfectly works. Interpretations like Bohmian mechanics have more serious problems (nonlocality, or retrocausality in transactional interpretation, etc). | |
| Jan 11, 2019 at 1:38 | comment | added | user65081 | @AliLavasani but why do you insist in interpreting it in the Copenhagen way, which is obviously the worst interpretation in physics ever! | |
| Jan 11, 2019 at 1:34 | comment | added | Alex L | @Wolphram Yes, any interpretation other that Copenhagen has no problem. Copenhagen shouldn't also fail, so my question is how the observation can have been done at the beginning of the universe. I don't know, maybe observation is done NOW when we look at the universe!! | |
| Jan 11, 2019 at 1:28 | comment | added | user65081 | @AliLavasani you can use the bohm interpretation too, it is less of a problem | |
| Jan 11, 2019 at 0:20 | comment | added | Alex L | You say there has been a "superposition" of all possible outcomes in the inflation, so what has destroyed the superposition? In Copenhagen, ONLY observation can collapse the superposition. If you believe it has automatically collapsed, you are defending "objective collapse" interpretations, and another option is that the universe is still in superposition (the many worlds interpretation). Either way you are implying one of these two kinds of interpretations, aren't you? | |
| Jan 10, 2019 at 23:35 | history | answered | user4552 | CC BY-SA 4.0 |