Cosmological Constant Problem

May 2014
142
11
Poole, UK
I suspect the likes of Sabine Hossenfelder and Eric Verlinde, understand how gravity works better than just about anyone on the planet.
If Sabine hossenfelder did, she'd know that she was wasting her time trying to quantize gravity. If Eric Verlinde did, he'd know he was wasting his time with entropic gravity. See Clifford M Will's paper The Confrontation between General Relativity and Experiment. General relativity is the best-tested theory we've got, but people like Hossenfelder and Verlinde ignore what Einstein said.

Both of them can derive Einstein's field equations using their methods. Verlinde requires no dark matter to explain why galaxies don't fly apart, I understand also Hossenfelder does not require as much dark matter to explain the galactic rotations as Einsteins field equations do.
They both ignore something else Einstein said: "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy”. A concentration of spatial energy causes gravity. Now take a look at the raisin-cake analogy, which says space expands between the galaxies but not within. So conservation of energy means every galaxy is surely sitting in a region of space where the energy density is greater than that of the surrounding space.

According to Verlinde both space and time are emergent. Also an additional interesting point is that many papers have been published in support of Verlindes theories and in addition to this Ricci flow is being used by other theoretical physicists to support Verlinde's theory. Of course Verlinde's theory is still under development.
To reiterate, I think that when you've read the Einstein digital papers, you understand how gravity works. Then I think you'd understand that entropic gravity is misguided. See what Wikipedia says:

"Entropic gravity, also known as emergent gravity, is a theory in modern physics that describes gravity as an entropic force—a force with macro-scale homogeneity but which is subject to quantum-level disorder—and not a fundamental interaction. The theory, based on string theory, black hole physics, and quantum information theory, describes gravity as an emergent phenomenon that springs from the quantum entanglement of small bits of spacetime information".

String theory is totally unproven, much of black hole physics contradicts general relativity, quantum information theory remains hypothetical, and we have no evidence whatsoever of "the quantum entanglement of small bits of spacetime information". Entropic gravity is speculation built on other speculations, and isn't in line with general relativity, which is the best-tested theory we've got. So I see no value in entropic gravity I'm afraid.
 
Sep 2019
41
4
Azores
" String theory is totally unproven, much of black hole physics contradicts general relativity, quantum information theory remains hypothetical, and we have no evidence whatsoever of "the quantum entanglement of small bits of spacetime information". Entropic gravity is speculation built on other speculations, and isn't in line with general relativity, which is the best-tested theory we've got. So I see no value in entropic gravity I'm afraid. "

I do recognize this forum only deals with standard model physics, however some Physics beyond the standard model, do predict most of what Einsteins theories do. Focusing on Verlinde, he derives exactly Einsteins field equations in the near range, only deviating in the long range where the volume law weakens and hands over to an area law. Yes there is a lot of speculation ie physics beyond the standard model in his theory. His theory has passed every test Einsteins General relativity did, in addition to which it does not need imaginary dark matter to explain the rotation curves of galaxies. Theories requiring imaginary matter to make them work may have had there day. Having said that Newtons theories are still used today within their limits, and GR will be used tomorrow but only in the short range where it complies with emergent gravity, unless some VALID reason for emergent gravity to be wrong is presented.

Various MOND theories exist which also dont need random amounts of dark matter. Verlindes arguments give those a theoretical basis also. Dark matter may well be death of GR
 
Jun 2016
1,198
565
England
These are topics on (or over) the boundaries of currently known physics,
and as such are wide open for all kinds of ideas and speculation.

I agree that Dark matter may well be death of GR, but there is a big "may" in there.

Physicists are well aware of the gaps and flaws in the current models,
which is precisely why the observations, currently modeled using Dark Matter, are so interesting,
because they might hold the promise of showing how these gaps could be filled.

However we are all still "shooting in the dark", hoping that the ongoing experiments, astronomical observations, etc...
will help to narrow down the currently wide open field of unbridled speculation.
 
Sep 2019
41
4
Azores
These are topics on (or over) the boundaries of currently known physics,
and as such are wide open for all kinds of ideas and speculation.

I agree that Dark matter may well be death of GR, but there is a big "may" in there.

Physicists are well aware of the gaps and flaws in the current models,
which is precisely why the observations, currently modeled using Dark Matter, are so interesting,
because they might hold the promise of showing how these gaps could be filled.

However we are all still "shooting in the dark", hoping that the ongoing experiments, astronomical observations, etc...
will help to narrow down the currently wide open field of unbridled speculation.
"Shooting in the dark" might be a bit strong.
"MAY" is not using unbridled speculation. E Verlinde mostly backs his speculations up with established theories.
Unbridled speculation ref what dark matter may or may not be has been around for years, and every experiment to detect has failed as far as I am aware. Which leaves me with the notion that an additional long range force might exist, could be more plausible than none existent dark matter.

PS the thread was about the cosmological constant problem, and the paper in the OP not Verlinde. I think we have drifted. Would it be possible to discuss Verlindes paper and possible supporting evidence on another thread or is it too hot to handle. ??????
 
Dec 2019
1
0
Nairobi
I was looking into Ricci Flow trying to get a better understanding of how space might evolve and stumbled across this paper, in which the author claims to have solved the Cosmological constant problem,

Ricci Flow Approach to The Cosmological Constant Problem M.J.Luo1 1Department of Physics, Faculty of Science, Jiangsu University, Zhenjiang 212013, People’s Republic of China In order to resolve the cosmological constant problem.


Is there anything wrong with his approach, or conclusion?
You might be interested in Unruh effect and Rindler space-time approach to the cosmological constant problem especially in evolving space-time in this paper. https://www.academia.edu/41271940/Unruh_effect_from_a_different_approach
 
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