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Does loop quantum gravity explain the dark matter effect (the rotational curves of the galaxies, the increased velocitoes of galaxies within galaxy clusters) without using dark matter?

As far as I understand LQG is about a granular nature of spacetime on the Planck scale. Therefore, it has nothing to do with dark matter at the first sight. However, some hopes might go in the direction of quantum gravity in general to explain the effect if one day everything is calculated through correctly.

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    $\begingroup$ Heard where? Which reference? Which page? $\endgroup$
    – Qmechanic
    Mar 31 at 18:15
  • $\begingroup$ No it does not. $\endgroup$
    – rfl
    Mar 31 at 18:51
  • $\begingroup$ I actually cannot find a source for that. Sorry for posting the wrong question. Maybe nevertheless answering it with rfl's answer? $\endgroup$ Apr 1 at 8:29
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    $\begingroup$ I don't think LQG is developed enough to be able to say anything about dark matter. $\endgroup$
    – Javier
    Apr 1 at 11:07
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    $\begingroup$ I haven't studied LQG in detail, but as I understand it is not known how to recover classical GR as a limit from LQG (see, eg, wikipedia), or how to couple the gravitational field to matter. So I'm not even sure LQG can explain the rotation of ordinary matter in a galaxy. $\endgroup$
    – Andrew
    Apr 1 at 15:18

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The trouble is explaining away dark matter, which is what you're really talking about, is only worth doing if dark matter being real is empirically worse.

Galaxies exist because the gravity in randomly extra-dense regions of space allowed such structure to form. Dark matter explains rotation curves etc.${}^\ast$ in terms of galaxies having however much baryonic and dark matter that region of space randomly had. Observations show either

  1. the relative amounts of each vary by galaxy and some galaxies have little if any dark matter, or
  2. if dark matter doesn't exist galaxies nonetheless behave as if (i) is correct.

Any proposed alternative to dark matter must explain all observational details in terms of 2. LQG doesn't do that. Indeed, nothing has yet done this well enough for 1 to be less plausible.

${}^\ast$ There are other reasons not to expect non-dark-matter explanations to succeed, such as the discernible baryonic/dark distinction in the Bullet Cluster.

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If you look back at my answer to your earlier question Arvin Ash said the following here “How do particles traverse this quantized space? When mass and energy are added to the spin foam the shape of the volumes of the spin network is distorted. This distorts space and time… This distortion of space and time is what we perceive as gravity.”

So based on his statement, gravity is caused by the distortion of space and time in LQG. So "dark matter" is not required for gravity, just this distortion which can be achieved with energy. "Dark Matter" should really be called "Dark Gravity".

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    $\begingroup$ this is certainly not a mainstream physics answer. $\endgroup$
    – rfl
    Apr 1 at 0:07
  • $\begingroup$ @rfl yes that is certainly true. But in the 120 years since special relativity, mainstream physics has yet to provide a plausible explanation for the cause of gravity. My paper closely ties dark matter and loop quantum gravity, so I thought it would be appropriate to answer the op. $\endgroup$ Apr 1 at 13:19
  • $\begingroup$ However, your answer doesn't explain anything. It only sums up which is already known and can be said by the sentence: "Gravity is distortion of spacetime and we do not know the origin of the dark matter effect" $\endgroup$ Apr 1 at 15:48
  • $\begingroup$ @BarrierRemoval Sorry, this was just an answer to the OP, which directed you back to your earlier question (from the same day) and to my paper. If you want the full theory of how time dilation, LQG, gravity and dark matter are related, you should take a look at my paper: vixra.org/abs/2202.0156 As rfl pointed out, it is outside of "mainstream physics", although I have provided sufficient references to back up the theory. $\endgroup$ Apr 1 at 16:10
  • $\begingroup$ I took another look at your comment above and I realized you missed the fact that what arvin ash said is that the little volumes or the particles of particulate space change shape with the adding of energy. So this is directly related to loop quantum gravity and particulate space. This becomes the very definition of the warping of SpaceTime. $\endgroup$ Apr 2 at 18:55

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