New Attractor, New Repeller

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New Attractor, New Repeller

Postby BurtJordaan on March 14th, 2017, 2:51 am 

Thought the Great Attractor sounded formidable? Well, think again - the more distant Shapley Attractor is now dwarfing it. As redshift data of thousands of 'nearby' galaxies were compiled and refined, no sooner had Shapley claimed the superior role, or a new phenomenon showed up, one that seems to be even more powerful: the Dipole Repeller.

Dipole Repeller.png
Shapley Attractor and Dipole Repeller (https://vimeo.com/189355968)


OK, it seems that they work together, the one "pulls" and the other one "pushes" our local group of galaxies, with a 'peculiar flow vector' (the yellow arrow)[1] of 630 km/s, almost directly away from the Dipole Repeller. The vector is probably the result of a combination of the more local pulls and the big "pullers and pushers" farther out. So what is a 'pusher', or rather a repeller?

I'm no astronomer (not even an amateur one), but as I understand things, astronomers combine the redshift data of the area of interest with other observations, e.g. mass densities, into a computer program to provide a 3D density map, as in the colors of the image. Using this, together with observed redshifts, they then model the motion of near-massless particles that they "seeded" the background with. This gives the flow-arrows as pictured. The animation in https://vimeo.com/189355968 is stunning!

The Dipole Repeller is just the minimum average density point of a large area of under-density, called a 'void'. In terms of gravitational potential, the repeller is a local maximum (gravity 'bump') and the attractor a local minimum (gravity 'well') for the are of interest.

Enjoy! (before we discuss this amazing result further).

Notes:
[1] Peculiar flow is our motion relative to the local inertial frame in which the CMB temperature would be the same in all directions, i.e. isotropic,
Last edited by BurtJordaan on March 14th, 2017, 3:55 am, edited 4 times in total.
Reason: End notes, clarification
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Re: New Attractor, New Repeller

Postby BurtJordaan on March 15th, 2017, 1:31 am 

BurtJordaan » 14 Mar 2017, 08:51 wrote:The Dipole Repeller is just the minimum average density point of a large area of under-density, called a 'void'. In terms of gravitational potential, the repeller is a local maximum (gravity 'bump') and the attractor a local minimum (gravity 'well') for the are of interest.

If you look at the potential values on the video frame above, it looks like it is the opposite of what I wrote above. The potential of the Attractor is given as Phi = +955 and for the Repeller Phi = -650. I had to read the technical article to find out why, because the gravitational potential function Phi is normally maximally negative at the center of a mass (a local Attractor) and can at most be zero in distant, empty space.

It appears that they are using the gravitational field strength as a potential that they call Phi - the potential to cause a flow velocity. A positive Phi then causes inflow into an Attractor, while there is obviously a negative inflow for a Repeller.

It is good to note that the Repeller is not creating any force, it is just a flow from higher (gravitational) potential energy to lower potential. This is why I like my interpretation more - it is rather intuitive... ;)
Last edited by BurtJordaan on March 15th, 2017, 6:01 am, edited 1 time in total.
Reason: Added paragraph
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