Erik P. Verlinde
2016 · arXiv
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional `dark' gravitational force describing the `elastic' response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton's constant and the Hubble acceleration scale a_0 =cH_0, and provide evidence for the fact that this additional `dark gravity~force' explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
Metadata: arXiv. Abstracts retain their original authors’ rights.
Original HN comments, with labels from simple text rules. A label describes the whole comment and may miss context or irony. Read the discussion to make up your own mind. About the labels
7 selected excerpts · 7 total mentions
I wonder how this relates to Erik Verlinde’s entropic gravity? https://arxiv.org/abs/1611.02269 It seems like this theory is proposing some entropic term on top of classical general relativity whereas Verlinde came up with a completely entropic theory of gravity. They both claim to explain dark matter.
Speaking of Bell's inequality, according to Erik Verlinde's theory on emergent gravity, gravity is an emergent force from the supersymmetry relationship of fundamental particles across the entirety of space and time. Each particle was encoded with a quantum memory state before a thermal energy source disrupted the tiny space and separated the paired particles across the galaxy. If this is true, I believe the observed violation of Bell's inequality could be explained by this pre space-time deterministic relationship that causes the force of gravity to emerge. https://arxiv.org/pdf/1611.02269.pdf
From the discussion section of Verlinde's paper[1]: > We have shown that the emergent laws of gravity, when one takes into account the volume law contribution to the entropy, start to deviate from the familiar gravitational laws precisely in those situations where the observations tell us they do. We have only made use of the natural constants of nature, and provided reasonably straightforward arguments and calculations to derive the scales and the behavior of the observed phenomena. [..] > In our view this undercuts the common assumption that the laws of gravity should stay as they are, and hence it removes the rationale of the dark matter hypothesis. Once there is a conceptual reason for a new phase of the gravitational force, which is governed by different laws, and this is combined with a confirmation of its quantitative behavior, the weight of the evidence tips in the other direction. [1]: https://arxiv.org/abs/1611.02269
'Kills off dark matter" is probably overstating the case, but I love this theory because it ties together a lot of big ideas. Verlinde's paper is here: https://arxiv.org/abs/1611.02269
Verlinde's paper [ https://arxiv.org/abs/1611.02269 ] is the wrong place to be looking for an argument against dark matter. It starts with simply accepting that dark energy is part of the unremovable background of spacetime (in particular, his paper considers a de Sitter vacuum with a straightforward positive cosmological constant, and treats it as fully described by classical General Relativity (GR)) and then proposes an emergent thermal-entropic force that may produce deviations from General Relativity on galactic and cluster scales by way of a long-distance entanglement among the fundamental material from which this take on perturbative gravity emerges. That…
fundamental material -- strings (sec 2.3) -- generating the thermal-entropic force does not feel electromagnetism, and so is dark. That fundamental material additionally is a component of the matter tensor in the low-temperature General Relativistic limit of his theory (eqn 4.23). Verlinde's theory is, in fact, a "cold" "dark" "matter" one; as the cosmological constant is involved too, it unsurprisingly reproduces the successess of \Lambda-CDM. (CDM == cold dark matter). The only qualification of this is that "matter" is the standard GR definition of everything that is not the gravitational field content. It's not much like the matter of the Standard Model (SM), while WIMPs are expected to be by virtue of some extension of the SM. (MACHOs, by contrast, can have very little to do with SM or extended-SM particles.) Nevertheless, the major difference between Verlinde's theory and the standard cosmology is the emergence of the standard cosmology from string theory. Quoting the paper: "in our ... framework one has to add a dark component to the stress energy tensor, which behaves very much like the cold dark matter needed to explain structure formation, but which in its true origin is an intrinsic property of spacetime rather than being caused by some unknown particle". In other words, the paper proposes that some (sec 8.2) of the dark matter of the standard cosmology can emerge from strings in a way that does not produce a particle like a heavy neutrino. (The paper is interesting many other ways, though.)
I'm not rejecting his theory because of pride or blindness. I'm rejecting it because I evaluated it with my brain and determined it to be bad. I'm saying that it is possible to 'know for sure' in some cases, insofar as my brain is working correctly. This is 2+2=5 stuff. I'm as sure he is wrong from reading his writing as I am sure that 2+2=4, because it's dead simple reading comprehension to be able to tell, if you have a bit of physics background. I'm telling you that it seems like you don't have the background to evaluate theories correctly, and so you should take note that this is a bad theory and if you think it sounds reasonable, you need to figure out why and…
correct that in your intuition. The level of expertise required to realize this guy is a moron is around first year undergraduate physics. That's all. I'm totally serious. Yes, I'm speaking with unearned authority, having no credentials to share or anything like that. All I can tell you is that I think I know my stuff and I am absolutely confident in my judgment here. There are theories that I would take seriously in the world. This is not one of them. This is an example of a recent paper that proposes a theory that is not part of mainstream acceptance, but is not obviously wrong and deserves consideration: https://arxiv.org/abs/1611.02269 . Note how different it looks. How it has math, arguments, and rigor. How it knows the current state of research in the field. How it isn't posted on a series of fringe websites that seem to all be owned by the same few people. How it doesn't have to tell you there's a conspiracy to suppress it, because its merits stand on their own. Also, you have to stop accusing me of 'not explaining my views' and 'thinking what academics or governments tell me to". I've written you several thousand words of my views, so those attacks are clearly baseless.
According to Verlinde, there is no dark matter. Tell me how he's wrong point-by-point. Just because gravity is emergent doesn't mean it still cannot have effects similar to what's been perhaps wrongly attributed to dark matter. You can't just say "Bullet Cluster" and "Dragonfly 44" and piss all over it without explanation. http://phys.org/news/2016-11-theory-gravity-dark.html http://www.forbes.com/sites/briankoberlein/2016/11/08/soluti... https://arxiv.org/abs/1611.02269
More from the same topics.
Anders Sandberg, Eric Drexler, Toby Ord
The Fermi paradox is the conflict between an expectation of a high {\em ex ante} probability of intelligent life elsewhere in the universe and the apparently lifeless universe we in fact observe.
Chiyuan Zhang, Samy Bengio, Moritz Hardt +2
Despite their massive size, successful deep artificial neural networks can exhibit a remarkably small difference between training and test performance.
Scott Aaronson
In honor of Alan Turing's hundredth birthday, I unwisely set out some thoughts about one of Turing's obsessions throughout his life, the question of physics and free will.
Tamara M. Davis, Charles H. Lineweaver
We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the Universe.