How a particle may stand still in rotating spacetime

May 25, 2018 by Lisa Zyga, Phys.org feature
When a particle with a certain angular momentum is located at the critical distance rst, it remains at rest while the spacetime is rotating around it. The closer a particle is to this critical distance, the slower it moves. Credit: Collodel et al. ©2018 American Physical Society

When a massive astrophysical object, such as a boson star or black hole, rotates, it can cause the surrounding spacetime to rotate along with it due to the effect of frame dragging. In a new paper, physicists have shown that a particle with just the right properties may stand perfectly still in a rotating spacetime if it occupies a "static orbit"—a ring of points located a critical distance from the center of the rotating spacetime.

The physicists, Lucas G. Collodel, Burkhard Kleihaus, and Jutta Kunz, at the University of Oldenburg in Germany, have published a paper in which they propose the existence of static orbits in rotating spacetimes in a recent issue of Physical Review Letters.

"Our work presents with extreme simplicity a long-ignored feature of certain spacetimes that is quite counterintuitive," Collodel told Phys.org. "General relativity has been around for a bit more than a hundred years now and it never ceases to amaze, and exploring the ways that different distributions of energy can warp the geometry of spacetime in a non-trivial way is key to a deeper understanding."

In their paper, the physicists identify two criteria for a particle to remain at rest with respect to a static observer in a rotating spacetime. First, the particle's angular momentum (basically its own rotation) must have just the right value so that it perfectly cancels out the rotation due to frame dragging. Second, the particle must be located precisely in the static , a ring around the center of the rotating spacetime at which the particle is neither pulled toward the center nor pushed away.

A key point is that not all astrophysical objects with rotating spacetimes have static orbits, which in the future may help researchers distinguish between different types of astrophysical objects. As the physicists explain, in order to have a static orbit, a rotating spacetime's metric (basically the function that describes spacetimes in general relativity) must have a local minimum, which corresponds to the critical distance at which the static orbit is located. In a sense, a particle may then be "trapped" at rest in this local minimum.

The physicists identify several that have static orbits, including boson stars (hypothetical stars made of bosonic matter that, like , have immense gravity but do not emit light), wormholes, and hairy black holes (black holes with unique properties, such as additional charge). On the other hand, Kerr black holes (thought to be the most common kind of black hole) do not have metrics with local minima, and so do not have static orbits. So evidence for a static orbit could provide a way to distinguish between Kerr black holes and some of the less common objects with static orbits.

While the acknowledge that it may be unlikely to expect a particle with just the right angular momentum to exist at just the right place in order to remain at rest in a rotating , it may still be possible to detect the existence of static orbits due to what happens nearby. Particles initially at rest near the static orbits are predicted to move more slowly than those located further away. So even if researchers never observe a particle standing still, they may observe slowly moving in the vicinity, indicating the existence of a nearby static orbit.

"Acknowledging the existence of the static ring helps us appreciate better what to plan and expect from future observations," Collodel said. "For instance, we can search for the ring in order to identify possible exotic objects, such as the boson star, or even assure with confidence (upon observing the ring) that an AGN [active galactic nucleus] is not powered by a Kerr black hole. In the future we plan to investigate how the presence of the ring might affect accretion disks, which are at this stage much easier to observe, and if it could shield some objects from infalling matter."

Explore further: Black holes, curved spacetime and quantum computing

More information: Lucas G. Collodel, Burkhard Kleihaus, and Jutta Kunz. "Static Orbits in Rotating Spacetimes." Physical Review Letters. DOI: 10.1103/PhysRevLett.120.201103

Also at arXiv:1711.05191 [gr-qc]

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Steelwolf
3.7 / 5 (3) May 25, 2018
So, if the hairy black hole, magnetar or bosun star is rotating fast enough, with it's massive gravity doing the frame dragging, there could be something like a planet or moonlet that would appear to be contradicting gravity by appearing to park near this massive frame dragging space-time and NOT 'Orbit' since it is the movement of the space-time of the frame dragging that gives it a virtual orbit so to the outside observer it would appear to stand still? That would be strange as all heck.
Whydening Gyre
3.3 / 5 (4) May 25, 2018
I like that they're considering a spacetime in rotation/motion.
As to a planet or moonlet sitting still in it? A black hole Lagrangian point, I guess...:-)
Steelwolf
1 / 5 (2) May 25, 2018
WG, doesn't the whole idea of frame dragging, especially to this level, more or less require an 'aether' of Some Sort? Certainly we have not pinned down exactly what it is, but if it can be bent (gravity lensing), stretched (red shift) and dragged with rotational frame dragging, it seems that there would Have to be a consistent field of some sort, or the framework for fields to hang themselves on.
Whydening Gyre
2.5 / 5 (2) May 25, 2018
WG, doesn't the whole idea of frame dragging ... seems that there would Have to be a consistent field of some sort, or the framework for fields to hang themselves on.

Indeed it does appear that way, however...
Understanding that fields(gravity being the most prominent, of course, followed by magnetic, EM and so on) extend themselves at the speed of light. And have been doing so for at least the last 13.7 billion years (I'm not a big fan of BB, but nothing else fits the model at this time, so....).
With literally trillions of observed gravitational bodies to date, that's a LOT of fields scattering around and interacting ... And the aggregate combination of all those interacting fields give the appearance of a larger framework. Possible even RESULTs in a framework field we call space/time...
I find THAT a simpler explanation to dispel the need for an "aether"...
(not to mention, "dark" anything...)
thingumbobesquire
not rated yet May 26, 2018
Did these theoreticians take into account so called dark energy's lambda effect on these supposed particles at complete rest?
ZoeBell
1 / 5 (1) May 26, 2018
physicists have shown that a particle with just the right properties may stand perfectly still in a rotating spacetime if it occupies a "static orbit"—a ring of points located a critical distance from the center of the rotating spacetime
Modified gravity theory also predict similar rings. Because these rings tend to concentrate particles trapped there, they could get occasionally stabilized by their own gravitational action there. IMO we already observed these rings at the case of large but rotating galactic clusters.
ZoeBell
1 / 5 (2) May 26, 2018
doesn't the whole idea of frame dragging, especially to this level, more or less require an 'aether' of Some Sort?
Of course but the same can be said about gravity, charge, magnetism or light waves itself. All these phenomena can be modeled by some inertial environment, which is both elastic, both superfluid at the same moment - the problem is, how to postulate this environment for to explain most wide range of phenomena observed. Once we must assume too much things about aether, then its predictive both explanatory power will vanish. The concept of quantum foam (suprafroth) is currently most close to these models.
TimLong2001
3 / 5 (2) May 26, 2018
Total BS.
ZoeBell
1 / 5 (2) May 26, 2018
@TimLong2001: try to recommend these topics (1, 2) for deletion after then. Also this recent article and many similar ones.
Osiris1
2 / 5 (4) May 26, 2018
That area of stability would be ideal for a ship powering an Alcubierre Warp Field Generator that generates the rotating space time field. Now if that rotating field was also varied by a time dependent function in three spatial dimensions, then a kind of 'baseball stitch' field could result that concentrates the compressed part of the spacetime in the back where it could 'expand' in 3D to the rear, and the 'rarified' part of the field in front where it could compress space in the kind of 6D (three of space translation and three of space rotation...all vectorial) + 3D of temporal 'time dragging' motion whose vectorial resultant would give direction to the ship/fields assembly.
I know that 97 + 04/100% will '1' this post because they do not understand it unless they are fluent in the Reynold's Equations in multivariable, multidegree partial differential coordinate equations form..... a critter from post grad fluid dynamics.
milnik
1 / 5 (2) May 27, 2018
Curved spatial time is to this day, so ruined the science that it will never recover from the debris and the contaminating properties that destroy our consciousness. If the science is gentle as well as from which the matter is formed, is it logical to draw conclusions that can not confirm anything in relation to natural laws. All such fatamorgans of science arise from the lack of understanding and ignorance of the basic natural rule, that there must be some substance from which matter is formed. Why are scientists so stubborn and unconscious that they reject the existence of Aether substance from which matter is formed, and with the help of "family relations", it forms gravity and magnetism. I'm sorry that science walks so much
Hyperfuzzy
not rated yet May 28, 2018
there are no particles
milnik
not rated yet May 29, 2018
there are no particles,
For you, the particles exhibit from the empty space, and since there is nothing there, then there are no particles. They are "dark" matter for you.
Hyperfuzzy
not rated yet May 29, 2018
there are no particles,
For you, the particles exhibit from the empty space, and since there is nothing there, then there are no particles. They are "dark" matter for you.

nonsense
Arginx
not rated yet May 31, 2018
@Steelwolf

U just explain perfectly how dumb this idea (theory) is. THANK YOU very much. ;-)
milnik
not rated yet Jun 01, 2018
@Hyp.
at your conclusion, everything visible, measurable and tangible in the universe is free of particles. So there are no: protons, neutrons, electrons, and so on, it's all that nobody knows what it is. Again, you returned to BB and back, when everything went through that point, it entered another universe where everything was lent, but there were no particles. Miracle over the wonders !!
Hyperfuzzy
not rated yet Jun 01, 2018
@Hyp.
at your conclusion, everything visible, measurable and tangible in the universe is free of particles. So there are no: protons, neutrons, electrons, and so on, it's all that nobody knows what it is. Again, you returned to BB and back, when everything went through that point, it entered another universe where everything was lent, but there were no particles. Miracle over the wonders !!

I do not know what you are smoking; but check your instrumentation. Pretty sure it measures the results of fields. Start with what is known. Charge. Is there a particle in its center? A Logical conclusion. No one owns logic! Try if yes, it has not been demonstrated. a neutron is composed of two, yet; particle? If none then a neutron, composite. Diametrical Spherical fields, no beginning, no ending
Hyperfuzzy
not rated yet Jun 01, 2018
the rest is simple algebra; better with dif eqs, even better with computers. asked for an ap from Wolfran; got told, "There are no electrons in nucleus
milnik
not rated yet Jun 01, 2018
It's stupid to continue the discussion !!
Hyperfuzzy
not rated yet Jun 01, 2018
It's stupid to continue the discussion !!

OK, imagine the life of all equal potential spheres about a charge at rest, relative to you. imagine the field updates as the center moves

now see it for all the charges this paper is talking about
donjoseph
not rated yet Jun 05, 2018
Mach introduced this concept using a rotating pail of water. If the observer is close enough and small enough same deal
Hyperfuzzy
not rated yet Jun 05, 2018
Mach introduced this concept using a rotating pail of water. If the observer is close enough and small enough same deal

it was a question about our observation, as we move and its relationship to what is observed, from the perspective of Geometry, a point has no spin; to be callous but respectful, there are no particles.

Spend more thinking about what we know for sure, a field, with a center, it's perfectly geometrical, what is it?

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