New Theory of Gravity Might Explain Dark Matter (phys.org)

vikingpower writes: Dutch prodigy and Amsterdam University Professor Erik Verlinde published a paper on arXiv yesterday, November 7, titled "Emergent Gravity and the Dark Universe." In the paper, Verlinde derives gravity from the so-called Holographic Principle, which -- simply put -- states that gravity emerges from the interplay between and entropy re-arrangement of sub-atomic "strings" that live in a negatively curved spacetime. At that level [...] spacetime and gravity are emergent from an underlying microscopic description in which they have no a priori meaning." Most importantly, Verlinde's paper has as a consequence that dark matter, nemesis of many an astronomer, is nothing more than an illusion. Verlinde, who was awarded the Dutch national Spinoza science prize in the recent past, already completed the tour de force of deriving Newtonian gravity from the same principles in a 2010 paper, also on arXiv. We are probably looking at Nobel-prize material here, as Verlinde is acknowledged by his peers to "go one better than Einstein's General Theory of Relativity." Slashdot reader turkeydance adds from a report via Forbes (Warning: source may be paywalled): As dark matter continues to vex astronomers, new solutions to the dark matter question are proposed. Most focus on pinning down the form of dark matter, while others propose modifying gravity to account for the effect. But a third proposal is simply to remove gravity from the equation. What if the effects of gravity aren't due to some fundamental force, but are rather an emergent effect due to other fundamental interactions? A new paper proposes just that, and if correct it could also explain the effects of dark matter.

Comments

Anti gravity?

[Anonymous Coward]

I must confess I'm completely out of my depth here (and not for the first time), but considering that gravity is now considered a dynamic process, would this open the way for anti-gravity devices?

If so within a week we went from nothing to a completely plausible sci-fi universe.. Reactionless drives, anti-gravity... FUN

Assumes entanglement

[Anonymous Coward]

If entanglement isn't real, then this isn't real.

If you have a system that imparts M independent properties onto N bodies. You then pre-filter based on time (using, say, a coincidence circuit), in effect selecting the subset of experiments for which the properties were imparted AT THE SAME TIME, and thus likely from the same event. Then if you measure each property, the others will correlate, DESPITE BEING INDEPENDENT.

In otherwords measure M1 of N1 and M1 of N2 and magically they will correlate. M2 of N1 and M2 of N2 will also correlate. It's not entanglement, it's not the act of measuring that set those properties to correlate, it was the pre-filtering that selected the *subset* of events for which those properties correlated.

So now apply Bells test to the UNfiltered data from the Delft entanglement experiment and you see entanglement isn't real. It fails the test. So entanglement isn't real.

So now they postulate a theory based on the entropy of qubits interconnected by entanglement is also not real. i.e. this postulate is not real:

"Our second postulate states that the quantum information measured by the area of de Sitter horizon spreads over all physical qubits in the bulk and hence becomes delo-calized into the long range correlations of the microscopic quantum state of the tensor network. By relaxing the stabilizer conditions, the quantum state of all bulk tensors is allowed to occupy a set of states O1 with a non-zero entropy density. Concretely this means that the tensors not only carry short range entanglement, but contain some indices that participate in the long range entanglement as well. The code subspace is thus contained in the microscopic bulk Hilbert space instead of the boundary Hilbert space. Since the quantum information is shared by all tensors, it is protected against disturbances created by local bulk operators, and therefore remains hidden for bulk observers. These delocalized states are counted by the de Sitter entropy, and contain the extremely low energy excitations that are responsible for the positive dark energy."

"When the volume becomes larger, due to the positive curvature of de Sitter space, the total quantum information stored by the collective state of the bulk tensors even- tually exceeds the holographic bound. At that moment the bulk states take over the entanglement, and local bulk operators are no longer mapped holographically to boundary operators. The breakdown of the area law entanglement at the horizon thus implies that de Sitter space does not have a holographic description at the horizon. The would-be horizon states themselves become maximally entangled with the thermal excitations that carry the volume law entropy. As a result they become delocalized and are spread over the entangled degrees of freedom that build the bulk spacetime."

Re:Is this string theory again?

[Anonymous Coward]

No. This is something different altogether. String theory never got as far as explaining even simple classical mechanics aspects. While there are a few hearty souls still plodding on, there is believed to be no real future for string theory.
 
Hey, if your theory is based on the sum of all integers being 1/12, you have a common sense problem... ;-)

Modeling error versus exotic matter

[sjbe]

Most importantly, Verlinde's paper has as a consequence that dark matter, nemesis of many an astronomer, is nothing more than an illusion.

This has been something I've been asking about for years with no good answer. Namely, what evidence exists to prove that so-called "dark matter" is actually matter rather than a defect in our mathematical model of gravity? Why is this not similar to how Einstein found a better model (relativity) for the phenomena first described by Newton? We're going through all sorts of contortions to try to prove that some mysterious "matter" must be there even though we have no idea what it could possibly be, have no direct observations, and our only evidence for it is inferred from our current models of gravity which we know to be incomplete since they do not work with quantum mechanics. While it certainly might be some form of exotic matter it seems at least equally probable that the answer might instead be that a better model is needed and that our current model is deficient in some way.

Re:Modeling error versus exotic matter

[painandgreed]

This has been something I've been asking about for years with no good answer. Namely, what evidence exists to prove that so-called "dark matter" is actually matter rather than a defect in our mathematical model of gravity?

It's like this. There are various evidence of something going on, such as galactic rotations, CMB patterns, gravitational lensing, etc. (These are described in the Wikipedia article on Dark Matter.) There have been, and currently still are, various explanations for these different evidences. Typically, we can do something like give each one a grade like the typical US grading scale of A-F. So far, the idea that there is matter out there that only interacts via gravity scores pretty highly A-C in all these. Other explanation such as MOND may score a B or even an A in one, but typically get an F in others. In the case of MOND, it doesn't even get an A in galactic rotations which seems a write in, because the resulting new law of gravitation would be so complicated that nobody has even proposed a hypothetical one that works in more than 2D solution, let alone addressing any of the other evidence on hand. Extraordinary claims require extraordinary support, and so far

It was the same approach with the origin of the moon. Lots of different theories but none really fit all the data until some serious computer simulations could be done in the late 80's to show that collision with another smaller mass caused ejection of mantle material was the best fit. Even then, it was added to as I think now it was ejection of two masses that later combined to form the moon.

Keep in mind that things like more normal matter, or MOND were first preposed 70+ years ago when the evidence was first seen. People have bene looking into them, testing them, coming up with different theories and after all that work, the current one for dark matter is the best we have to fit all the evidence. So, just because we leave out cat food and it disappears is not reason to think we have a cat we've never seen, but at this point, the cat food is being eaten, the litterbox is being used, cat toyed are being moved under couches in the middle of the night, and at times if we knock on the walls, we can hear something meow back at us. Still never seen the cat and can't proves it's there, but if it's something other than a cat doing all this stuff, the new answer is going to be a lot weirder than the explanation of a cat we've never seen.

Re:Cue The Usual Suspects

[david_thornley]

From your summary, it sounds like the paper attempts to explain galactic rotation curves. Does it have anything to say about gravitational lensing where there's no apparent matter?