Meaning of time in the multiverse theory

[MysticWizard]

TL;DR Summary

Question/Thought experiment about time in the quantum mechanical mutiverse theory

From Wikipedia: Suppose a six-sided die is thrown and that the result of the throw corresponds to quantum mechanics observable. All six possible ways the dice can fall correspond to six different universes. In the case of the Schrödinger's cat thought experiment, both outcomes would be "real" in at least one "world".

This statement got me thinking, would it be possible for 1 universe (out of the infinite collection of universes) to be stationary infinitely alternating between state A & B, or using the dice analogy throwing a 1 and a 2 over and over effectively making this universe appear looped in time? Further extrapolating on this, using the quantum xeno effect, would it be possible to be stuck on one outcome not changing unless "something" stops measuring/observing? And last, would it be possible to go "back in time" where all outcomes up till a point occur in reverse order?

I understand that the chances of this happening are very small but if I am not mistaken in an infinite collection of universes not 0

Or did I miss a key property of QM that makes this impossible?

Thanks in advance for your insights!

 

[physika]

..."infinite" collection of universes...

how ?
Sure ?

.

 

[PeroK]

I don't understand your question at all.

 

[256bits]

Summary: Question/Thought experiment about time in the quantum mechanical mutiverse theory

Or did I miss a key property of QM that makes this impossible?

If I get your gist, is it that you are asking whether the quantum wave function can collapse in the split off universes, where the collapse 'seems real', except but one'? If so, it doesn't really make sense since it is all the possible outcomes of the collapsing wave function that allow the multiple universes to form.
For the die, each throw has six possible outcomes, resulting in six split off universes,
Throwing multiple times produces a 'new' wave function collapse each time.
In your universe you are throwing alternating 1's and 2's, but not in the other 5 split off universes on each throw.

 

[MysticWizard]

I don't understand your question at all.

Ok perhaps the following analogy helps getting across what I am struggeling with. What if a quantum state can be thought of a a single frame in a film. Now there is 1 universe where the quantum state keeps collapsing to the same state over and over which would result in a film where time appears to stand still. Or is there some property that makes this analogy flawed?

 

[PeterDonis]

there is 1 universe where the quantum state keeps collapsing

You appear to be using the many worlds interpretation of QM, since you talk about "multiverse theory"; but in the MWI, there is no collapse of the quantum state.

 

[MysticWizard]

You appear to be using the many worlds interpretation of QM, since you talk about "multiverse theory"; but in the MWI, there is no collapse of the quantum state.

I did not realize this! Amazing. I'll have to read up on what this means and what the consequences might be. Thanks for your answer!

 

[PeroK]

Ok perhaps the following analogy helps getting across what I am struggeling with. What if a quantum state can be thought of a a single frame in a film. Now there is 1 universe where the quantum state keeps collapsing to the same state over and over which would result in a film where time appears to stand still. Or is there some property that makes this analogy flawed?

QM is probabilistic. Take, for example, radioactive decay. Each atom decays probabilistically. But, because of the huge number of atoms, and the law of large numbers, the overall process becomes predicable and reliable. And we have predicable carbon dating, for example.

This seems to be a conundrum for some people who cannot reconcile individual atomic probabilities with the predictability of the macroscopic process.

 

[PeroK]

PS if you take MWI literally, then there are branches of the universal wavefunction where radioactive decay has never taken place! But, these branches have such a vanishingly small probability that I'm dubious of their physical significance.

 

[PeterDonis]

Moderator's note: Thread moved to the QM interpretations forum since the OP is basing their question on the MWI.

 

[PeterDonis]

these branches have such a vanishingly small probability that I'm dubious of their physical significance.

According to the MWI the "weight" of a branch does not matter as far as its physical significance: every branch "exists" regardless of its weight. Doubting the physical significance of branches with very small weights means doubting the MWI: but of course there are also many other reasons why people doubt the MWI.

 

[Demystifier]

Summary: Question/Thought experiment about time in the quantum mechanical mutiverse theory

This statement got me thinking, would it be possible for 1 universe (out of the infinite collection of universes) to be stationary infinitely alternating between state A & B, or using the dice analogy throwing a 1 and a 2 over and over effectively making this universe appear looped in time? Further extrapolating on this, using the quantum xeno effect, would it be possible to be stuck on one outcome not changing unless "something" stops measuring/observing? And last, would it be possible to go "back in time" where all outcomes up till a point occur in reverse order?

I understand that the chances of this happening are very small but if I am not mistaken in an infinite collection of universes not 0

Or did I miss a key property of QM that makes this impossible?

Thanks in advance for your insights!

I think your question makes much more sense if you replace the word "multiverse" with the word "statistical ensemble". The statistical ensemble is just a tool for thinking about probability, so your question is really: Is there a non-zero probability, no matter how small, that such things happen? A short answer is: Yes!

 

[PeroK]

According to the MWI the "weight" of a branch does not matter as far as its physical significance: every branch "exists" regardless of its weight. Doubting the physical significance of branches with very small weights means doubting the MWI: but of course there are also many other reasons why people doubt the MWI.

If these branches were physically significant, then the statistically based laws of QM would not be reliable. That's what I take physical significance to mean.

We don't have to consider the possibility that radioactive decay suddenly stops taking place - even in a single specific case. Not to mention microelectronics relying on electron tunnelling etc.

 

[PeterDonis]

If these branches were physically significant, then the statistically based laws of QM would not be reliable.

Why not? "Physically significant" is a much wider category than "significant for the set of observations that humans have actually made or could make now or in the foreseeable future".

 

[physika]

Question/Thought MULTIVERSE THEORY
This statement got me thinking, would it be possible for 1 universe (out of the INFINITE collection of universes)

there is not an INFINITE collection of universes
in a MULTIVERSE MODEL.

How many universes are in the multiverse?
Andrei Linde, Vitaly Vanchurin.
https://arxiv.org/PS_cache/arxiv/pdf/0910/0910.1589v1.pdf

"We argue that the total number of distinguishable locally Friedmann universes generated by eternal inflation is proportional to the exponent of the entropy of inflationary perturbations and is limited by e^{e^{3 N}}, where N is the number of e-folds of slow-roll post-eternal inflation. For simplest models of chaotic inflation, N is approximately equal to de Sitter entropy at the end of eternal inflation; it can be exponentially large."

10^10^10^7

10¹⁰¹⁰⁷

in any case not infinite

.