Supercomputer shows 'Chameleon Theory' could change how we think about gravity

Supercomputer shows 'Chameleon Theory' could change how we think about gravity
Computer generated images showing a disk galaxy from a modified gravity simulation.Images show (right side of image, in red-blue color) the gas density within the disk of the galaxy with the stars shown as bright dots. The left side of the images show the force changes in the gas within the disk, where the dark central regions correspond to standard, General Relativity-like forces and the bright yellow regions correspond to enhanced (modified forces). Images show views of the simulated galaxy from above and the side. Credit: Christian Arnold/Baojiu Li/Durham University.

Supercomputer simulations of galaxies have shown that Einstein's theory of General Relativity might not be the only way to explain how gravity works or how galaxies form.

Physicists at Durham University, UK, simulated the cosmos using an alternative model for gravity—f(R)-gravity, a so called Chameleon Theory.

The resulting images produced by the simulation show that galaxies like our Milky Way could still form in the universe even with different laws of gravity.

The findings show the viability of Chameleon Theory—so called because it changes behaviour according to the environment—as an alternative to General Relativity in explaining the formation of structures in the universe.

The research could also help further understanding of dark energy—the mysterious substance that is accelerating the expansion rate of the universe.

The findings are published in Nature Astronomy.

General Relativity was developed by Albert Einstein in the early 1900s to explain the gravitational effect of large objects in space, for example to explain the orbit of Mercury in the solar system.

It is the foundation of modern cosmology but also plays a role in everyday life, for example in calculating GPS positions in smartphones.

Scientists already know from theoretical calculations that Chameleon Theory can reproduce the success of General Relativity in the solar system.

The Durham team has now shown that this theory allows realistic galaxies like our Milky Way to form and can be distinguished from General Relativity on very large cosmological scales.

Research co-lead author Dr. Christian Arnold, in Durham University's Institute for Computational Cosmology, said: "Chameleon Theory allows for the laws of gravity to be modified so we can test the effect of changes in gravity on galaxy formation.

Supercomputer shows 'Chameleon Theory' could change how we think about gravity
Computer generated images showing a disk galaxy from a modified gravity simulation are available. Images show (right side of image, in red-blue color) the gas density within the disk of the galaxy with the stars shown as bright dots. The left side of the images show the force changes in the gas within the disk, where the dark central regions correspond to standard, General Relativity-like forces and the bright yellow regions correspond to enhanced (modified forces). Images show views of the simulated galaxy from above and the side. Credit: Christian Arnold/Baojiu Li/Durham University.

"Through our simulations we have shown for the first time that even if you change gravity, it would not prevent disc galaxies with spiral arms from forming.

"Our research definitely does not mean that General Relativity is wrong, but it does show that it does not have to be the only way to explain gravity's role in the evolution of the universe."

The researchers looked at the interaction between gravity in Chameleon Theory and supermassive black holes that sit at the centre of galaxies.

Black holes play a key role in galaxy formation because the heat and material they eject when swallowing surrounding matter can burn away the gas needed to form stars, effectively stopping star formation.

The amount of heat spewed out by black holes is altered by changing gravity, affecting how galaxies form.

However, the new simulations showed that even accounting for the change in gravity caused by applying Chameleon Theory, galaxies were still be able to form.

General Relativity also has consequences for understanding the accelerating expansion of the universe.

Scientists believe this expansion is being driven by dark energy and the Durham researchers say their findings could be a small step towards explaining the properties of this substance.

Research co-lead author Professor Baojiu Li, of Durham University's Institute for Computational Cosmology, said: "In General Relativity, scientists account for the accelerated expansion of the universe by introducing a mysterious form of matter called dark energy—the simplest form of which may be a cosmological constant, whose density is a constant in space and time.

"However, alternatives to a cosmological constant which explain the accelerated expansion by modifying the law of gravity, like f(R) , are also widely considered given how little is known about dark energy."

The Durham researchers expect their findings can be tested through observations using the Square Kilometre Array (SKA) telescope, based in Australia and South Africa, which is due to begin observations in 2020.

SKA will be the world's largest radio telescope and aims to challenge Einstein's of General Relativity, look at how the first stars and formed after the Big Bang, and help scientists to understand the nature or dark energy.


Explore further

Video: 100 years of gravity

More information: Christian Arnold et al, Realistic simulations of galaxy formation in f(R) modified gravity, Nature Astronomy (2019). DOI: 10.1038/s41550-019-0823-y
Journal information: Nature Astronomy

Provided by Durham University
Citation: Supercomputer shows 'Chameleon Theory' could change how we think about gravity (2019, July 8) retrieved 20 October 2019 from https://phys.org/news/2019-07-supercomputer-chameleon-theory-gravity.html
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Jul 08, 2019
Spinning sphere theory, uses relativity to show that the universe does have limitations in size, but it also predicts multiverses, and multimultiverses, and hidden dimensions. Please see "Predicting the Gravitational Constant from the New Physics of a Rotating Universe"

Jul 08, 2019
The very name suggests a revolt against an anchor of modern scientific theory: parsimony. In other words, for every environment there are enough dials and switches in the theory to fiddle with to make everything turn out all right anyway.
In contrast, with General Relativity, all the dials and switches are in the input data themselves; they go into the GR black box, and out pops a solution.

Jul 08, 2019
There are some very complicated issues of galaxy formation. Unfortunately, here is the same problem as with the stars. The origin of galaxies remains unclear, in spite of huge activity in the field. What the "formation" means? It means that we have the material that is assembling into galaxies.
https://www.acade...ome_From
https://www.acade...osmology

Jul 08, 2019
"The research could also help further understanding of dark energy..."

So could a more realistic model of the universe. The simplifications—usually swept under the rug—are put to the light in the new "Dark Energy Dialogue." Arguments are made, both for and against, a more complex model. Illustrated in a clear and engaging manner.

YouTube: https://youtu.be/4goInwbOix4

Jul 08, 2019
Must admit that I haven't read much about the various chameleon theories...so I will over the coming days. However, in this article with regard to DE they refer to it as a 'substance'. Just seemed a little odd to me.

Jul 08, 2019
Changing some parameters and constants in space-time equations and then throwing them into a computer does not actually make it a "theory" But what stands out in this poorly written summary is hubris: "Our research definitely does not mean that General Relativity is wrong..." I suggest that even if the Durham team directly contradicted GR with their Chameleon "theory", then they would still have a very long way to go before turning the page on Albert Einstein.

Jul 08, 2019
A similar point has been made at the microscopic scale with the less generalized example being pilot wave theory, or anything else more complete that produces the same results for the Bell inequalities, local realism, non-locality, etc. Looking forward to the properly trained AI verifying the correct answer for these questions at all scales is 42. Seriously though, spotting patterns in arrays of numbers is what it does best, so give it as much valid data as there is... let it feast on some LIGO data :)

Jul 09, 2019
"have shown that Einstein's theory of General Relativity might not be the only way to explain how gravity works"

No shit sherlock , Where did the concept of "Visible" matter actually originate ?
Freaking thieving Maggots!

Jul 09, 2019
Dark matter is a supersolid that fills 'empty' space, strongly interacts with ordinary matter and is displaced by ordinary matter. What is referred to geometrically as curved spacetime physically exists in nature as the state of displacement of the supersolid dark matter. The state of displacement of the supersolid dark matter is gravity.

The supersolid dark matter displaced by a galaxy pushes back, causing the stars in the outer arms of the galaxy to orbit the galactic center at the rate in which they do.

Displaced supersolid dark matter is curved spacetime.

The supersolid dark matter displaced by the Earth, pushing back and exerting pressure toward the Earth, is gravity.

In the Bullet Cluster collision the dark matter has not separated from the ordinary matter. In the Bullet Cluster collision the galaxy's associated dark matter displacement waves have separated from the colliding galaxies.

Jul 09, 2019
It's paywalled, they use "hydrodynamical simulations." I don't think hydrodynamical simulations can recreate fields that appear to be composed of spin-2 bosons. I think they're overcomplicating it and wasting everyone's time. Maybe that's what they want to do.

Jul 09, 2019
I think hydrodynamical simulations would produce dense spin-1 vector fields where each vector represents molecular-type-level flow or inertia and is heavily influenced by surrounding field vectors. There's no reason to think they can be combined into mutually-oppositely-rotating pairs for a decent galaxy-scale spiral-type or Hoag's-like gravity effect.

Jul 09, 2019
Still trying MOND. Read the abstract; "modified gravity" occurs more than once. This is MOND.

Jul 09, 2019
More specifically I meant hydrodynamic flow carriers can't be combined into adjacently-located mutually-oppositely-ultraslowly-rotating pairs. I'm not suggesting the gravity flow carriers on opposite sides of a galaxy are behaving as if possibly entangled, in other words. Not ruling it out either.

Jul 09, 2019
Da Schneib wants everyone to know the only way to modify gravity is to use Milgrom's modified inertial dynamics, but modified inertial dynamics is not really modified gravity, and Da Schneib is not really worth reading except if you want to be reminded of his political views on gravity and how he likes to pander to the lowest common math-skills denominator segment out there.

Jul 09, 2019
MOND is like hydrodynamics with a leftward or rightward circular water-cannon squad positioned around the perimeter. Let's pretend it's brilliant stuff, I mean, but gravity modification? Only if you insist and I have no vote.

Jul 09, 2019
It's paywalled, ...
There's an eprint on arXiv -- Realistic simulations of galaxy formation in f(R) modified gravity

Jul 09, 2019
Thanks, @Proto. Still looks like MOND to me.

Jul 09, 2019
There's an eprint on arXiv


Thanks, but hydrodynamical simulations of galaxy-scaled gravity are a waste of time.

Take a look at Hoag's Object, imagine the ring was not a result of a collision but instead an accumulation. Assume the core forms a static wave to support the ring, consider vector rotation as multiplication of a hydrodynamic-type of flow by a cosine with a galaxy-sized static-phase wavelength.

Dirac tried rescaling basic particle sizes to cosmological sizes based on E/G force-ratio while letting G vary, in my opinion the cosine wave multiplier here works much better than Dirac's ideas.

Anyway as the ring grows in mass through accumulation it may self-gravitationally constrict, pushing core mass out of the galactic plane and deforming it into a bar. The bar then drops to the galactic plane and disrupts the gravity symmetry at the inner edge of the ring, bisecting the ring, pulling in two opposite ends from the two ring halves and eventually forming spiral arms.

Jul 09, 2019
I'm saying the uncanny balanced symmetry of so many pairs of galactic spiral arms is a spin-2 property.

Seeing galactic symmetry as a gravity spin-number-influenced thing is probably not new, but I believe it has to work at the quantum scale to produce a convincing set of balanced spiral arms. It's a quantum gravity wavelength that comes from rescaling effective proton radius 10^-15 meters by the dimensionless E/G ratio of proton-to-proton forces 10^+36. 10^+24 meters is common scale for galaxies, It is the rescaling of one ubiquitous object size scale, charge-dominated nucleonic scale, to a gravity-dominated ubiquitous-object size scale - galactic scale - around 100,000 light-years.

Jul 09, 2019
Still looks like MOND to me.
Hmm, I think you'd have to call it MOP (for modified physics) or MOGR (for modified GR) -- referring to equation (1) in the paper, it's stated, "The theory is constructed by adding a scalar function f(R) of the Ricci scalar R to the Einstein-Hilbert action of GR". They're literally adding a fifth force to the known 4, and they're actually preserving Newtonian dynamics in dense regions like a solar system by using a screening mechanism.

Thanks, but hydrodynamical simulations of galaxy-scaled gravity are a waste of time.
From the paper, "... the model can pass the stringent constraints on gravity in the solar system and still leave detectable signatures on large scales, making it an excellent tool to explore how possible deviations from GR would be observable."

Jul 09, 2019
Still trying MOND. Read the abstract; "modified gravity" occurs more than once. This is MOND.


It's not MOND. Modified Gravity is more the general name given to the class of models which explore modifications to GR on cosmological scales. f(R) is one of those models but there are dozens. Original MOND wasn't even relativistic so it is not even in the same class as f(R). The vast majority of the interest was in explaining the apparent acceleration of the universe without Lambda, removing the problem of fine tuning with the cosmological constant. MOND on the other hand was about dark matter, this paper has nothing to do with MOND. The whole point of projects like Euclid, DESI and LSST is to pin down the nature of acceleration, understanding alternative models to LCDM is a necessary step.

Jul 09, 2019
"The theory is constructed by adding a scalar function f(R) of the Ricci scalar R to the Einstein-Hilbert action of GR"

Is this gravity landscape shaped like a depressed trampoline but made of cascaded giant waterfall step functions embodied with walls having flow-restrictors near the top? Only gravity-driven thing I can think of at the moment. Sorry. It seemed overdesigned.

Jul 09, 2019
As I saw it a long time ago, MOND was an attempt to preserve most all of gravity but it involved changing distributed galactically-peripheral inertia, peripheral resting points became drifting galaxy-circumlocuting points which meant decoupling peripheral GR gravity from inertia in general. Gravity had nothing to do with the drifting, I mean less gravity the better for it. Later when it was noted to have nothing to do with gravity lensing, the media spinners decided it was a modified gravity theory failing at the cluster scale.

Jul 09, 2019
Thanks, @IMP. At least this one has testing criteria.

Jul 10, 2019
I would like to propose a modified gravity theory that also explains these phenomena, including the reason for the formation of ring galaxies. This theory also explains the odd acceleration of Oumuamua, the interstellar asteroid that recently passed through our solar system:

https://redd.it/ao8vfo

Jul 10, 2019
Please take a look.

Jul 11, 2019
Please take a look
Note how the amplitude of the undulating anomalous acceleration predicted by eq(1) is ever more pronounced as the distance r decreases, and in the "Testing and Falsification" section the importance of observing the motion of probes or objects is stressed. So it would be advantageous to observe an object whose orbit passes through the larger undulations nearer the sun.

As luck would have it, a new Atira asteroid was recently discovered whose 151-day orbit takes it from outside the orbit of Venus all the way to inside the orbit of Mercury. See 2019 LF6 -- does the observed motion of this object support or falsify the predictions of eq(1) ?

Jul 11, 2019
"... the model can pass the stringent constraints on gravity in the solar system and still leave detectable signatures on large scales, making it an excellent tool to explore how possible deviations from GR would be observable."

Seems they may evince an attitude of supporting an exhaustive set of possible variations on gravity, simply owing to altering a scalar value relevant to GR and to hydrodynamic flow simulations, but there is no way a hydrodynamical simulation can ever generate flows reflective of spin-2 field quanta properties, yet spin-2 field quanta are, in my opinion, responsible for supporting galaxy-rings that bifurcate into balanced arms.

Jul 11, 2019
I suggested there is no way a hydrodynamical simulation can ever generate flows reflective of spin-2 field quanta. I guess you could consider rate-controlled counter-rotating heat-conductive rings separated by a layer of lubricant (recently noted by experimenters to behave somewhat counter-entropically) to be an approximate sort of exception. Gravity's spin-2 carrier galactic ring supporting aspect is another thing making gravity counter-entropic, in my opinion. Most examples of gravity limiting entropy are, I suppose, capturable with hydrodynamics and spin-1 flow field quanta, (simple restricted flow vectors) however they are relatively mundane.

Jul 11, 2019
Most examples of gravity limiting entropy are, I suppose, capturable with hydrodynamics and spin-1 flow field quanta, (simple restricted flow vectors) however they are relatively mundane.
Have you looked at Penrose's conformal cyclic cosmology re gravity and entropy by any chance?

Jul 11, 2019
-- does the observed motion of this object support or falsify the predictions of eq(1) ?


Thank you for posting this. Detailed analysis of the motion of an asteroid like this does indeed have the potential to falsify the idea. I would very much like to see experts do such an analysis. One of the implications of my hypothesis is that acceleration anomalies observed in comets may be due to the fluctuation in the Sun's gravity and NOT off-gassing, as current theory supposes.

As for the asteroid, because of its high velocity, the small fluctuations in acceleration caused by gravity might be missed, especially because increased acceleration in some portions of the orbit may be cancelled out by negative acceleration in other portions. But you are completely correct in that a detailed analysis of the trajectory might definitely falsify the idea.

Jul 11, 2019
Penrose is super-clever, I've followed his stuff for decades. I avoid taking cosmology too seriously. Poisson had a cyclic recurrence concept a long time ago, seems the same in instinct, I don't know.

Jul 11, 2019
This apparently relates to the CCC: "The equations governing the crossover from each aeon to the next demand the creation of a dominant new scalar material, postulated to be dark matter. In order that this material does not build up from aeon to aeon, it is taken to decay away completely over the history of each aeon."

If you look at Hoag's Object and imagine the core has generated a sort of circular gravity-raceway, a static valley-ripple, it's not hard to imagine GR theorists underestimating Hoag's central core mass by fitting a parabolic curve to the roll-off in radial velocity at the edge of the central mass, and it's easy to imagine them adding dark matter at the periphery to rapidly tow around the matter constrained by the raceway-effect in the static gravity ripple. The core-radiated gravity valley of the ripple may have a notable lensing effect whether or matter fills the ring. MOND makes ring-region stuff speed up without using ring-region gravity, so w/o peripheral lensing.

Jul 11, 2019
@Joe1963 -- yup, comets seem like the next best option for such observations. Have you thoroughly evaluated results of the Rosetta mission? Couldn't ask for better measurements than in situ.

It may also be helpful to compare your effort with that of the physicists at Durham. Note how f(R) has physical meaning -- from the paper, "The theory introduces an extra scalar degree of freedom which mediates a fifth force between matter particles." In your eq(1) there's a constant inside a sine function: 0.00004 -- what's the physical connection for that? Does it imply a fifth force?

Also note what IMP-9 pointed out about f(R) being in a class of models that are alternatives to GR, and aren't MOND. It relates to your effort because your eq(1) predicts the greatest variance in regions where the constraints are strongest -- from the paper, "GR has been empirically verified, to remarkably high precision, on small scales ..."


Jul 11, 2019
In your eq(1) there's a constant inside a sine function: 0.00004 -- what's the physical connection for that? Does it imply a fifth force?


Disclaimer: I am an amateur for whom this has been more of a logical exercise rather than "science." I would like to explain my logical steps:

1. Assume that there is no such thing as "dark matter" or "dark energy."
2. Assume that the following unexplained motions are due to the simple working of gravity: a) galactic rotation rates, b) cosmological expansion, c) the odd acceleration of Oumuamua.
3. Since some of these motions are attractive, and some repulsive, this suggests a wave-like variation.
I just played with constants to get a wave function that was approximately consistent with regular gravity for the planets in our solar system. I realize it is data-fitting, but it is just throwing a hypothesis out there. I am not qualified to offer much more than this. If interested to discuss: joebakhos@yahoo.com

Jul 11, 2019
If you look at Hoag's Object and imagine the core has generated a sort of circular gravity-raceway...
I look at Hoag's Object and imagine agreeing, yeah, a Dyson sphere is small potatoes. Did AREPO (or any model) make any ring galaxies? Pretty amazing formation to see...

Jul 15, 2019
Lol they should be brave enogh to call einstein's GR, as utter bunk. But they may lose funding and their jobs, if they do

Aug 02, 2019
I think that this star's motion out of our galactic center might also be explained by a repulsive-gravity idea:

https://www.yahoo...195.html

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