Multiple (Non-Interacting) Universes?

[Suekdccia]

TL;DR Summary

Different versions of the universe that do not interact between them means that there could be multiple worlds in a many worlds interpretation like manner?

Before anything, I would like to clarify that I am aware that this is speculative physics more than established mainstream physics (and Smoot is not claiming that his ideas are true). However I think that it is interesting to discuss these models even if they are not yet proven to be right.

I was reading an interesting paper by Nobel laureate Mr. George Smoot (https://arxiv.org/abs/1003.5952) where he assumes the holographic principle as true and conjectures that our universe would be encoded on the "surface" of an apparent horizon as the weighted average of all possible histories. In that way, there would be one world (or universe) that would be the average among all possible worlds.

However, I was not sure if Smoot refers to our Universe is the actual one in the sense that this is the one that we observe while the other histories would exist as (unobserved) different worlds (like in the Many Worlds Interpretation), so I sent him an email. After some time he replied. However I'm not still sure of what he means. Could you help me understand what he said:

I sent him:

>(...) Couldn't there be other apparent horizons, and therefore, other universes that are the result of the average of all possible histories in those horizons?
And also, in your model, could there be any situation where the other histories would be considered as real (similar to the many worlds interpretation) instead of only one being real?

And he basically replied that his view does hold that many different versions of the Universe coexist with very different weightings and that it is likely one is in a version with high weighting and it is likely most of the high weightings are similar.
He added that, however, they are forbidden to communicate and interact just like things outside the horizon: If they communicated and interacted, then they would be part of the same Universe version.

Does it sound like he meant that other universes would exist and would be real but they could neither interact nor communicate (similar to the worlds in the Many Worlds Interpretation)?

 

[PeterDonis]

Moderator's note: Thread moved to Beyond the Standard Model forum.

 

[ohwilleke]

Summary: Different versions of the universe that do not interact between them means that there could be multiple worlds in a many worlds interpretation like manner?

The many worlds interpretation basically requires interaction between different universes as earlier ones give rise to later ones. So, different non-interacting worlds wouldn't really fit.

 

[Motore]

The many worlds interpretation basically requires interaction between different universes as earlier ones give rise to later ones.

Not really. According to Everett, once you find yourself in a different branch (world) of the universal wave function you cannot interact with another branch (world).

 

[Suekdccia]

The many worlds interpretation basically requires interaction between different universes as earlier ones give rise to later ones. So, different non-interacting worlds wouldn't really fit.

I agree with Motore, in the Many World interpretation the different worlds do not communicate between each other (that, among many other reasons, is why so many physicists reject it as no evidence could be gathered from them to infer that they exist, in principle, at the very least)

 

[Suekdccia]

Not really. According to Everett, once you find yourself in a different branch (world) of the universal wave function you cannot interact with another branch (world).

So, with that definition, does it appear to you that Smoot is talking about these different "versions" of the Universe as different non-interacting, but existing worlds (as Everett would have defined them in his interpretation)?

 

[PeterDonis]

The many worlds interpretation basically requires interaction between different universes as earlier ones give rise to later ones.

What are you referring to here? In the MWI, different "worlds" (meaning different branches of the wave function which have decohered) do not interact. A process in which an earlier universe "gives rise to" a later one would be a process happening over time in one "world" (one branch of wave function).

 

[ohwilleke]

What are you referring to here? In the MWI, different "worlds" (meaning different branches of the wave function which have decohered) do not interact. A process in which an earlier universe "gives rise to" a later one would be a process happening over time in one "world" (one branch of wave function).

The notion would be that a past universe/branch is interacting with multiple future branches that can arise from it, so there is an interaction at specific branching points in space-time-"branch space". I'm not suggesting that there is interaction between branches once they have split.

 

[PeterDonis]

The notion would be that a past universe/branch is interacting with multiple future branches that can arise from it

That's not "interaction", it's just time evolution in the MWI. As you note, it doesn't mean multiple branches that exist at the same time can interact with each other.

 

[Suekdccia]

What are you referring to here? In the MWI, different "worlds" (meaning different branches of the wave function which have decohered) do not interact. A process in which an earlier universe "gives rise to" a later one would be a process happening over time in one "world" (one branch of wave function).

So, with that definition, does it appear to you that Smoot is talking about the different "versions" of the Universe mentioned in his paper as different non-interacting, but existing worlds (as Everett would have defined them in his MWI)?

 

[PeterDonis]

does it appear to you that Smoot is talking about the different "versions" of the Universe mentioned in his paper as different non-interacting, but existing worlds (as Everett would have defined them in his MWI)?

The best person to answer that question would be Smoot. What he says could be interpreted that way, but I don't know Smoot's attitude towards the MWI. Some physicists like it, others don't.

 

[physika]

So, with that definition, does it appear to you that Smoot is talking about the different "versions" of the Universe mentioned in his paper as different non-interacting, but existing worlds (as Everett would have defined them in his MWI)?

I think, not like MWI
In Smoot model diverses universe exist but separated, in a sort of non interacting, independent and autonomous existence (IMO).
No Branching.

.