Mathematical proof: The current model of the expanding universe is not viable.

R

Roosters for ever

Registered Senior Member

Taking dark energy out of the equation: Mathematicians challenge the standard cosmological model of the universe:​


Mathematicians are challenging the idea that dark energy is responsible for the accelerating expansion of the universe. In a new paper published in Proceedings of the Royal Society A, mathematicians from the University of California, Davis, provide mathematical proof that instabilities inherent in the Einstein-Euler equations imply that the current model of the expanding universe is not viable.

The Einstein-Euler equations are a union of general relativity and fluid dynamics equations used to model astronomical phenomena such as galaxies, black holes, and cosmic expansion.

The research directly challenges the Lambda-cold dark matter model, the standard cosmological model of the Big Bang.

Study corresponding author Blake Temple, a distinguished professor emeritus of mathematics at UC Davis, compared the standard cosmological model to a pencil standing on its tip.

"All the forces are in balance when a pencil is standing on end, so it is a 'solution of the equations,'" he said. "But it's unstable. Any breath of air and it falls away."

The mathematics, Temple said, prove that Friedmann spacetimes—mathematical models that govern cosmic expansion—are unstable at both small and large length scales at the Big Bang, making it the most unstable solution of all.

"Unstable solutions in physics and science are considered not physical," Temple said. "You'll never observe them in nature."

Temple noted that this instability suggests a simpler explanation—one based entirely within the framework of Einstein's original theory.
more at link....



A further paragraph says....
"However, the cosmological constant, and the idea that it's interchangeable with dark energy, was reintroduced to explain the universe's accelerating expansion in the 1990s. Standard cosmological models are based on what's called the "Friedmann universe," which describes all matter as expanding but being evenly distributed throughout space at each fixed time".
Question:
Matter as expanding??? Isn't it spacetime expanding and matter being taken for a ride, so to speak? is this just a typographical error?
Question:
Is it mathematical proof that Einstein's original equations were right without the CC?
Question:
A further paragraph claims...
"We prove that, like Einstein's static model, the Friedmann spacetimes are all unstable to radial perturbation at large length scales," Temple said. "This appears to rule out the Lambda-cold dark matter model as a viable stable solution of the Einstein equations of general relativity, with or without dark energy."
Question:
Does it?

Further it concludes, "
"The math also calls into question the Copernican principle—the idea that Earth's location does not occupy a special place in the universe". "Both the Lambda-cold dark matter model and a spherically symmetric spacetime produce a special place where we must lie for the model to be physically plausible," Temple said. "If this principle rules out one, it has to rule out the other."
Question:
Wow! That to me is a big call! Any comments?

Question:
Is this simply science doing what science does best? Always questioning itself, always considering further observations and data? or as per the scientific method, do we simply wait it out for further research and possible data on any updating of the current model of Universal evolution?.
 
Roosters for ever said:
"The math also calls into question the Copernican principle—the idea that Earth's location does not occupy a special place in the universe". "Both the Lambda-cold dark matter model and a spherically symmetric spacetime produce a special place where we must lie for the model to be physically plausible," Temple said. "If this principle rules out one, it has to rule out the other."
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Without doing any further investigation at all, this strikes me as implausible on its face.

In what way does Temple think the Earth's location is a special place in the universe? Does he say?
 
James R said:
Without doing any further investigation at all, this strikes me as implausible on its face.
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Hence my questions, reflecting surprise and (I hope) some doubt.
James R said:
In what way does Temple think the Earth's location is a special place in the universe? Does he say?
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He does say the maths calls it into question.
And again I hope I expressed some surprise at least, if not, again doubt. "Wow! That to me is a big call! Any comments?"
The paper:

The instability of critical and underdense Friedmann spacetimes at the Big Bang as an alternative to dark energy.​



I again conclude with the question/statement, "Is this simply science doing what science does best? Always questioning itself, always considering further observations and data? or as per the scientific method, do we simply wait it out for further research and possible data on any updating of the current model of Universal evolution?."
 
EXCERPT: Standard cosmological models are based on what's called the "Friedmann universe," which describes all matter as expanding but being evenly distributed throughout space at each fixed time. But the math didn't add up to Temple and his colleagues, leading them to pursue alternative explanations for the accelerating expansion of the universe.

"We prove that, like Einstein's static model, the Friedmann spacetimes are all unstable to radial perturbation at large length scales," Temple said. "This appears to rule out the Lambda-cold dark matter model as a viable stable solution of the Einstein equations of general relativity, with or without dark energy."

"This means," he added, "that the Big Bang should generically look exactly like a Friedmann spacetime near the center of symmetry, but generically one should observe accelerations away from Friedmann far from the center."
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So the Earth is potentially some sort of "special place" because it happens to be one of the worlds near "the center of symmetry"[???], with our local situation thereby generating biases or affecting conclusions about expansion in general? I.e., engendering the view that the latter is very homogenous or the same everywhere -- ergo, historically and still currently causing the Friedman depictions of spacetime to be favored?

Apparently #8 below is extracting "small angular dependence" in the CMB from something in this [25]paper: On the large-angle anomalies of the microwave sky. Note the "Accelerations over and above Friedmann spacetimes have a centre of expansion and this has historically been viewed as a violation of the Copernican principle." Such areas of space would be uniquely expanding in a way that departed from the general conception of expansion?
  • https://royalsocietypublishing.org/...20/The-instability-of-critical-and-underdense

    EXCERPTS: The Friedmann family of spacetimes describe a uniform three-dimensional Universe of galaxies expanding in time from an initial Big Bang singularity at a rate determined by Einstein’s field equations. [...] In the early 1930s, Howard Robertson and Arthur Walker anchored the acceptance of cosmology based on Friedmann spacetimes with the so called Copernican principle, by establishing mathematically that if there is no special place in a three-dimensional Universe of galaxies, made precise by the condition that space be homogeneous and isotropic about every point, then any such three-space evolving in time according to Einstein’s field equations must indeed be a Friedmann spacetime.

    This connected the Friedmann spacetimes with prescientific notions of Earth not being in a special place in the Universe, a sort of principle of physics more or less accepted as a justification in the community of established cosmologists since that time. The high degree of uniformity in the microwave background radiation and distribution of the galaxies lend strong support to the Copernican principle, supporting the starting assumption that the Universe of galaxies is, on the largest scale, a Friedmann spacetime, implying the existence of a Big Bang singularity at some initial time. Fluctuations in the microwave background radiation argue strongly for the critical (___) Friedmann spacetime, the unique self-similar member of the Friedmann family in which the expanding three-space at each fixed time is perfectly flat.

    A major challenge to this theory arose in 1999 with the discovery of the anomalous acceleration of the galaxies based on supernova data. To maintain the critical Friedmann solution and consistency with both the Einstein field equations and the observed expansion rate of the galaxies based on that data, the cosmological constant was introduced back into Einstein’s equations for late time cosmology, interpreted as dark energy.

    [...] #1. By Friedmann spacetimes, we mean the family of Friedmann–Lemaître–Robertson–Walker spacetimes with zero cosmological constant, parameterized by curvature constant ___.

    [...] #4. A non-zero cosmological constant is not needed in physical confirmations of Einstein’s theory other than for cosmology. Furthermore, since the energy density decreases like ___ and ___ is constant, the ACDM model also places the Universe in a special place in time when the energy density of classical matter and dark energy are on the same order, a different seeming violation of the Copernican principle and the hallmark of using an ad hoc correction to the equations when it is the underlying solution that is wrong.

    [...] #8. Accelerations over and above Friedmann spacetimes have a centre of expansion and this has historically been viewed as a violation of the Copernican principle. Note that there is a small angular dependence in the microwave background radiation and all current models seem to place Earth in some sort of special place, suggesting to the authors that some violation of the Copernican principle might be something we are forced to accept.
 
Roosters for ever said:
Matter as expanding??? Isn't it spacetime expanding and matter being taken for a ride, so to speak? is this just a typographical error?
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Sloppy writing more likely. The authors seem to understand that it's ST expanding, so I suspect their expanding matter is just a shorthand for that

I'm all for silencing the lambda, but seems like it's still early days on this question. I need to understand more about this "standing pencil" of instability. I find that analogy suspicious.
 
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