Multiverse and observational evidence?

In summary: WMAP and Planck satellites. In this paper, we compute limits on these entanglement effects from the Planck CMB data combined with the BICEP/Keck polarization measurement, and find no evidence for observable modulations to the power spectrum from landscape entanglement, and no sourcing of observable CMB anomalies."In summary, the recent attention on cosmologist Laura Mersini-Houghton's multiverse model, which proposes that the cosmic microwave background (CMB) is created when universes separate, may be due to the publication of her book "Before the Big Bang: The Origin of the Universe and What Lies Beyond." However, her model has not been verified
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Cosmology and multiverse are beyond my limited knowledge, but I came across the following article that aroused my curiosity. Although I am extremely cautious with "exotic" theories, I'd like to read any comments on that part of the article that a model proposed by cosmologist Laura Mersini-Houghton has found some sort of verification in CMB measurements.
https://www.theguardian.com/science...ersini-houghton-before-the-big-bang-interview
 
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  • #2
apostolosdt said:
Cosmology and multiverse are beyond my limited knowledge, but I came across the following article that aroused my curiosity. Although I am extremely cautious with "exotic" theories, I'd like to read any comments on that part of the article that a model proposed by cosmologist Laura Mersini-Houghton has found some sort of verification in CMB measurements.
https://www.theguardian.com/science...ersini-houghton-before-the-big-bang-interview
I don't understand

"When the process of separation [of universes] happens, that’s the point when the cosmic microwave background (CMB) is created"

I thought that was OUR Universe, decoupling?

@Orodruin @PeterDonis @phinds lots of others but those for now
 
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  • #3
I hope other more knowledgeable folks will chime in but I have two comments. First, I abhore all the multiverse theories but that's a personal preference/opinion. Second, I find her comment "When the process of separation [of universes] happens, that’s the point when the cosmic microwave background (CMB) is created." to be just weird. The CMB is just the Surface of Last Scattering and is not something that happened like flipping a light switch but rather something that occurred over a significant amount of time (in human terms anyway, not so much is cosmological terms but still, NOT instantaneous). How that can translate to a "decoupling of universes" does not make sense to me but again, I'm biased against such theories.
 
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  • #4
I guess, it's just an example that even serious newspapers tend to emphasize esoterics also in scientific news. That's of course much simpler than trying to explain the research to laymen in a proper way. It's only quite disturbing that the scientist in this case obviously approved this kind of statements within her interview. Does anybody know, to which research paper this new coverage refers to?
 
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  • #5
vanhees71 said:
I guess, it's just an example that even serious newspapers tend to emphasize esoterics also in scientific news. That's of course much simpler than trying to explain the research to laymen in a proper way. It's only quite disturbing that the scientist in this case obviously approved this kind of statements within her interview. Does anybody know, to which research paper this new coverage refers to?
I don’t know why the sudden attention now, but this paper from 2019 appears to be the one being discussed:

https://arxiv.org/abs/1807.10833
 
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Although I don't understand any details of string theory or the landscape multiverse this sounds much more scientific than the Guardian article suggests, as expected. Maybe somebody with more expertise on string theory can evaluate this in more detail.
 
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apostolosdt said:
a model proposed by cosmologist Laura Mersini-Houghton has found some sort of verification in CMB measurements
"Verification" is too strong. All this really amounts to is "for this particular data, our multiverse model's predictions happen to be indistinguishable from those of standard non-multiverse inflation models, so we can say we match the data as well as they do".

What would actually count as "verification" is something like "for this particular data, our model makes a correct prediction and other models make an incorrect prediction". No multiverse model has done that, nor do I expect one to any time soon.
 
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apostolosdt said:
I'd like to read any comments on that part of the article that a model proposed by cosmologist Laura Mersini-Houghton has found some sort of verification in CMB measurements.
https://www.theguardian.com/science...ersini-houghton-before-the-big-bang-interview

The abstract from

https://arxiv.org/abs/1606.00672

by Will Kinney:

"We consider observational limits on a proposed model of the string landscape in inflation. In this scenario, effects from the decoherence of entangled quantum states in long-wavelength modes in the universe result in modifications to the Friedmann Equation and a corresponding modification to inflationary dynamics. Previous work by Holman, Mersini-Houghton, and Takahashi suggested that such effects could provide an explanation for well-known anomalies in the Cosmic Microwave Background (CMB), such as the lack of power on large scales and the "cold spot" seen by both the WMAP and Planck satellites. In this paper, we compute limits on these entanglement effects from the Planck CMB data combined with the BICEP/Keck polarization measurement, and find no evidence for observable modulations to the power spectrum from landscape entanglement, and no sourcing of observable CMB anomalies."
 
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  • #9
George Jones said:
The abstract from

https://arxiv.org/abs/1606.00672

by Will Kinney:

"We consider observational limits on a proposed model of the string landscape in inflation. In this scenario, effects from the decoherence of entangled quantum states in long-wavelength modes in the universe result in modifications to the Friedmann Equation and a corresponding modification to inflationary dynamics. Previous work by Holman, Mersini-Houghton, and Takahashi suggested that such effects could provide an explanation for well-known anomalies in the Cosmic Microwave Background (CMB), such as the lack of power on large scales and the "cold spot" seen by both the WMAP and Planck satellites. In this paper, we compute limits on these entanglement effects from the Planck CMB data combined with the BICEP/Keck polarization measurement, and find no evidence for observable modulations to the power spectrum from landscape entanglement, and no sourcing of observable CMB anomalies."
Can you say some or all of that so I can understand a little bit better please George? I am not a physicist.
Edit. Is the CMBR a certain amount of time after the big bang, 300,000 years?
And, I thought inflation was fractions of after the BB. Multiverses after that?
 
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  • #11
George Jones said:
The abstract from

https://arxiv.org/abs/1606.00672

by Will Kinney:

"We consider observational limits on a proposed model of the string landscape in inflation. In this scenario, effects from the decoherence of entangled quantum states in long-wavelength modes in the universe result in modifications to the Friedmann Equation and a corresponding modification to inflationary dynamics. Previous work by Holman, Mersini-Houghton, and Takahashi suggested that such effects could provide an explanation for well-known anomalies in the Cosmic Microwave Background (CMB), such as the lack of power on large scales and the "cold spot" seen by both the WMAP and Planck satellites. In this paper, we compute limits on these entanglement effects from the Planck CMB data combined with the BICEP/Keck polarization measurement, and find no evidence for observable modulations to the power spectrum from landscape entanglement, and no sourcing of observable CMB anomalies."
While this is relevant to the overall history of this discussion, this paper is from 3 years before Mersini-Houghton's latest model from the paper I linked above.
 
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1. What is the multiverse theory?

The multiverse theory proposes that there are multiple universes beyond our own, each with its own set of physical laws and properties. It suggests that our universe is just one of many in an endless expanse of space and time.

2. What is the observational evidence for the multiverse theory?

Currently, there is no direct observational evidence for the existence of the multiverse. However, some theories such as inflation and string theory provide mathematical support for the concept of a multiverse. Additionally, some observations such as the cosmic microwave background radiation and the distribution of galaxies in the universe can be interpreted as potential evidence for a multiverse.

3. How does the multiverse theory explain the fine-tuning of the universe?

One of the main arguments for the multiverse theory is its ability to explain the fine-tuning of our universe. It suggests that with an infinite number of universes, it is likely that at least one would have the necessary conditions to support life. Therefore, our universe's apparent fine-tuning is not a result of chance but rather a product of the vastness of the multiverse.

4. Can the multiverse theory be tested?

At this time, the multiverse theory cannot be directly tested due to the limitations of our current technology and understanding of the universe. However, as our technology and knowledge continue to advance, scientists may develop new ways to test and gather evidence for the multiverse theory.

5. How does the multiverse theory impact our understanding of the origin of the universe?

The multiverse theory challenges traditional ideas about the origin of the universe, such as the Big Bang theory. It suggests that our universe may have been created through a process of eternal inflation, where new universes are constantly being formed. This idea expands our understanding of the origins of the universe and raises new questions about the nature of reality.

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