Was Einstein wrong? Why some astrophysicists are questioning the theory of space-time

rod

Oct 22, 2019
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I found 19 references to *quantum* in this article, 0 references to *cosmological constant*. The Cosmological Constant Is Physics’ Most Embarrassing Problem, https://www.scientificamerican.com/article/the-cosmological-constant-is-physics-most-embarrassing-problem/, Feb-2021.

Einstein GR and QM are in serious conflict here describing expanding space. Without the metrics from GR, there is no math describing the expansion of space, redshifts apparently, and cosmological distances using redshifts. Another comment in this report from Scientific American, “One of the first people to notice something was amiss was physicist Wolfgang Pauli, who found in the 1920s that this energy should be so strong that the cosmos should have expanded long past the point where light could traverse the distance between any of the objects in it. The whole of the observable universe, Pauli calculated, “would not even reach to the moon.” He was reportedly amused by his estimation, and no one took it seriously at the time. The first to formally calculate the value of the cosmological constant based on quantum theory's predictions for the vacuum energy was physicist Yakov Zel'dovich, who found in 1967 that the energy should make the cosmological constant gigantic.” That suggest using QM, space is expanding so fast, we should not be here today :)
 
Jan 4, 2020
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Started to skip the content as soon as the article appealed to revolutions instead of quantifiable science. Hossenfelder is fringe, LQG is both fringe and doesn't work (no dynamics due to no harmonic oscillator model) and as it happens we know full well that quantum gravity makes the field and its particles behave like any other relativistic field.

As Weinberg says in his recent review on where effective quantum field theory is, which he is one of the co-discoverer of:

Similar remarks apply to gravitation, which I think has led to a new perspective on general relativity. Why in the world should anyone take seriously Einstein’s original theory, with just the Einstein–Hilbert action in which only two derivatives act on metric fields? Surely that’s just the lowest order term in an infinite series of terms with more and more derivatives. In such a theory, loops are made finite by counterterms provided by the higher-order terms in the Lagrangian. This point of view has been actively pursued by Donoghue and his collaborators.
[ https://link.springer.com/content/pdf/10.1140/epjh/s13129-021-00004-x.pdf ]

An Effective Field Theory is one which uses only the active degrees of freedom available at some energy. A full quantum field theory treatment is applied. When done properly, the results encode the quantum corrections appropriate to that energy. The perturbative treatment of quantum General Relativity behaves as an effective field theory, and well defined quantum corrections can be calculated. This review discusses effective field theory and its application to general relativity.

The problem of quantum gravity is not what we once thought it was. If you go back to early references, you will find many statements saying that general relativity and quantum mechanics are incompatible, that the combination of general relativity and quantum field theory produces a meaningless theory. It is understandable that some of the pioneers may have thought in this way, as some of our quantum methods are awkward when dealing with general relativity. However, these statements are not correct.
[ http://www.scholarpedia.org/article/Quantum_gravity_as_a_low_energy_effective_field_theory ]

That space is 3D flat is a result of cosmology, not quantum field theory as such.
 
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I found 19 references to *quantum* in this article, 0 references to *cosmological constant*.
The article is so fringe that I had to stop being lazy and find the article discussion.

The low value of the vacuum energy density is not a principle problem, albeit many physicists still become apoplectic when facing the natural consequences of inflation. However, interestingly the entire eBOSS 20 year spectroscopic galaxy survey collaboratioon just published through peer review a short list containing at front and center the long noted eternal inflation multiverse solution of the same Nobel Laureate Stephen Weinberg that I cite in my own response to the article.

Nevertheless, the observed consistency with flat ΛCDM at the higher precision of this work points increasingly toward a pure cosmological constant solution, for example, as would be produced by a vacuum energy fine tuned to have a small value. This fine-tuning represents a theoretical difficulty without any agreed-upon resolution, and one that may not be resolvable through fundamental physics considerations alone [224,225]. This difficulty has been substantially sharpened by the observations presented here.
[ https://authors.library.caltech.edu/108974/1/PhysRevD.103.083533.pdf ; "[224] S. Weinberg, Rev. Mod. Phys. 61, 1 (1989)."]

The sophistic response is that it is still fringe. But that is an arguiable position now that hundreds of cosmologists in a major survey stuck their jaw out. I also recently discovered that its formal test has been suppressed by the common description of the history - in fact Weinberg hypothesized the low energy density range before it was observed and you can find papers pointing that out.

Einstein GR and QM are in serious conflict here describing expanding space. Without the metrics from GR, there is no math describing the expansion of space, redshifts apparently, and cosmological distances using redshifts.
As my own response to the article show, that is a historical artefact, akin to how people still refer to quantum "duality" despite that quantum field theory explicitly solved that just after its proposal (particles being localized ripples in a wave functional field). I promote Donoghue's comment on that again:

The problem of quantum gravity is not what we once thought it was. If you go back to early references, you will find many statements saying that general relativity and quantum mechanics are incompatible, that the combination of general relativity and quantum field theory produces a meaningless theory. It is understandable that some of the pioneers may have thought in this way, as some of our quantum methods are awkward when dealing with general relativity. However, these statements are not correct.
Space is 3D flat with a relativistic Lorentzian metric factor regardless of gravity, and gravity is an added field in its quantum field theory, explicitly described in Wilczek's "core theory" based on Feynman path integrals:



[ https://www.preposterousuniverse.com/blog/2013/01/04/the-world-of-everyday-experience-in-one-equation/ ]

Adding relativity space expansion to its earlier time dilation and length contraction* doesn't seem like a big deal. This is perhaps more fringe, but it testably works and it has central players in quantum field theory promoting it. None of the other quantum gravity hypotheses are like that.

The last part of the comment skip over inflation, where that fact that causal disconnect of previously connected space volumes happened solves many problems. The apparent finetuning of the vacuum energy since the hot big bang has a natural - but for some infuriating - explanation. Or something else explains, but at least we have hypotheses.

Again, the natural eternal inflation would disempower the question what space is, since in that physics it has always existed and its energy density therefore sums to zero of an infinite time ground state. (Albeit frustrated, as our hot big bang shows, inflation lies at naturally somewhat higher potential energies.) It is consistent and it solves the general relativity problem of localizing energy on the cosmological scale - there is no net energy to localize - I'll give it that. But this time it is quite obviously fringe notions (though arguably promising, eternal inflation has solidified dueing the Planck collaboration era findings).

*Or as some now argues, its wavefunction collapse induction - need no change to quantum physics, just making the action quantum h universal akin to the universal speed limit c -putting all the exotic phenomena under the same hat. I believe I have commented on length here on that after I discovered the work on that, so see those comments for references.

Of those phenomena, time dilation is the least exotic since gravity mostly manifest due to the high value of the universal speed limit: your feet aging slower than your head is what mostly keeps your head up and feet down to Earth.
 
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I also recently discovered that its formal test has been suppressed by descriptions - Weinberg hypothesized the low energy density range before it was observed.
Going off topic for the article but not the context rod mentioned, I have considered the analogy between habitability proxies.

Weinberg used the vacuum energy range allowing galaxies as a hard and fast minimum criteria for habitability of universes. Many of those will still not see intelligent life. Some others may do it despite lacking galaxies.

Analogously, astrobiologists use the habitable zone surface water conditions as a hard and fast minimum criteria for habitability of planets. Many of those will still not see intelligent life. Some others may see life, at least, despite lacking surface water (c.f. ice moons).

When astronomers only knew our planetary system and saw only one habitable planet, did they propose more systems and more life? Well, yes, but they saw other stars and they couldn't say that "Earth exist and has life therefore more planets must exist and have life". The hypothesis seemed reasonable. Certainly not something to get apoplectic over, but at the same time astronomers now criticize the minimalistic nature of the search targeting criteria. But the hypothesis was weak until the various tests seeing more planets came along. Astronomers were never certain they could in fact see other planets until they did.

One can see that the analogy is not identity. Life evolved so quickly and diversifies so rapidly here that few biologists question its existence somewhere else now that we can see planets. But we still need to test that!
 
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rod

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My observation. I like c.g.s. units to examine cosmology and inflation expansion speeds. The CMBR is said to form about 380,000 years after the BB event so 1.198 x 10^13 seconds later. Inflation is said to take place perhaps 10^-36 to 10^-32 second after BB event, still a long way from Planck time apparently (10^-44 or 10^-45 second). So we have 10^-36 second after BB until the CMBR forms where H0 apparently is 69 km/s/Mpc (or in that range like today's values for H0). Converting to cm/s/cm we have 3D space expanding at 2.236 x 10^-18 cm/s/cm since at least the CMBR formed and today using measurements for H0. Inflation? This features 3D space expanding >= 3 x 10^31 cm/s, ref - https://www.scientificamerican.com/custom-media/biggest-questions-in-science/the-founder-of-cosmic-inflation-theory-on-cosmologys-next-big-ideas/

This looks like a wonderous cosmological transformation in the origin of the universe starting at 10^-36 second after BB until about 1.2 x 10^13 second after the BB event where in the early universe replusive gravity existed and 3D space expanding >= 10^21 c velocity and now we see H0 today in the area of 10^-18 cm/s/cm.

All of this exotic soup in the beginning evolved just right during the time interval 10^-36 second after BB until about 1.2 x 10^13 second after BB and then onto the present age some 4.35 x 10^17 seconds later or after BB event, and here we are today to read all about it :)
 
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Yes, it is an exciting physics!

Though I'm not sure "repulsive gravity" is the correct terminology since gravity is per definition always attractive - curves space - while space expansion (of, say, non-curved flat space) depends on the matter-energy content of space.

The relative expansion of the universe is parametrized by a dimensionless scale factor a. Also known as the cosmic scale factor or sometimes the Robertson Walker scale factor, this is a key parameter of the Friedmann equations.

In the early stages of the Big Bang, most of the energy was in the form of radiation, and that radiation was the dominant influence on the expansion of the universe. Later, with cooling from the expansion the roles of matter and radiation changed and the universe entered a matter-dominated era. Recent results suggest that we have already entered an era dominated by dark energy, but examination of the roles of matter and radiation are most important for understanding the early universe.
[ https://en.wikipedia.org/wiki/Scale_factor_(cosmology) ]

Inflation is said to take place perhaps 10^-36 to 10^-32 second after BB event, still a long way from Planck time apparently (10^-44 or 10^-45 second).
This is, like "the problem of gravity" as Donoghue calls it, an historical artefact. The majority of cosmologists accept inflation and the younger generation seem to adhere to what that physics tells us - that we observe not a big bang cosmology but an inflationary hot big bang cosmology.

Among most people who study the early Universe, inflation is accepted as the new consensus theory. We might not know everything there is to know about inflation, but either it — or something so similar to it that we don't have an observation to tell them apart — must have happened
An inflating Universe doesn't begin in a singularity like a matter-dominated or radiation-dominated Universe does. All we can state with certainty is that the state we call the hot Big Bang only came about after the end of inflation. It says nothing about inflation's origins.
There are a lot of people who mean "the initial singularity" when they say "the Big Bang," and to those people, I say it's long past due for you to get with the times. The hot Big Bang cannot be extrapolated back to a singularity, but only to the end of an inflationary state that preceded it. We cannot state with any confidence, because there are no signatures of it even in principle, what preceded the very end-stages of inflation. Was there a singularity? Maybe, but even if so, it doesn't have anything to do with the Big Bang.

Inflation came first, and its end heralded the arrival of the Big Bang. There are still those who disagree, but they're now nearly a full 40 years out of date.
[ https://www.forbes.com/sites/startswithabang/2019/10/22/what-came-first-inflation-or-the-big-bang/?sh=701987074153 ]

[That is by the way the cosmology that Weinberg used to predict the low vacuum energy value. If inflation exist - "or something so similar to it that we don't have an observation to tell them apart" - it keeps naturally going on indefinitely. Those volumes that haven't yet locally "banged" expand faster and inflating space will naturally dominate, you have to finetune it not to do so. And inflationary multiverse doesn't need to be the actual physics, but it looks like the simplest outcome based on current observations.]
 
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rod

Oct 22, 2019
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"Yes, it is an exciting physics!", post #7. Reference my post #6. I note this about BB model chiefly supported by Einstein GR metrics for expanding 3D space.

Consider the BB cosmology model. By 1.198 x 10^13 seconds after BB event, the CMBR forms (about 380,000 years later). Today we are at 4.352 x 10^17 seconds after BB (about 13.8 billion years later). So time expands some 10^4 magnitude and space expands just right to make the universe we see today. 3D space expanding at the rate of some 10^-18 cm/s/cm (H0 = 69 km/s/Mpc) should do the trick. However, just a bit of nudge here can alter everything and make the universe younger than 8 billion years old (or no universe here at all today) 😊

Converting to logarithmic scale from when the CMBR forms and present age (13.8 billion vs. 8 billion years in seconds), Log 4.56 vs. Log 4.32 can alter everything in the expanding universe and the cosmological constant can blow the universe apart too :)

"Yes, it is an exciting physics!" I agree :)
 
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I believe I have an idea on how space/time can curve to create these quantum effects we see in micro-cosmos.
Black hole is a kind of makro- cosmic quantum object that is explained my general relativity.
A black hole have boundaries like in quantum physics.
So the thing is to explain micro-cosmos with the relativity theory.

A gravity wave that pass earth with the speed of light make the speed of time jiggle just like the length dimensions jiggle they detect with LIGO.
Lets say something can happen that create a gravity wave that is so intense that when it pass earth time stop or go incredibly fast at the moment the gravity wave pass earth.
Lets say the universe can create a gravity wave where time go incredibly fast.
If we are outside we will se this person all over the gravity wave.
The person in the wave will see the universe stop outside and he can travel inside the wave and look at the universe in that frosen moment.
The wave pulse is a singularity in the shape of a expanding spheric shell that expand with the speed of light in every direction.

I believe these pulses exists also in micro cosmos and explain these quantum problems.
I believe Albert Einstein was right.

Regards MagI
 
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