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Dark matter, is it real?

Started by Bluenose, November 18, 2021, 11:41:43 PM

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Bluenose

Found this video, might be of interest to some here. It certainly poses some interesting questions.  I haven't found the paper described in it, but then I have not really looked...   ::)

https://youtu.be/0sTBZ2G4vow
+++ Divide by cucumber error: please reinstall universe and reboot.  +++

GNU Terry Pratchett


Recusant

Fine stuff, thank you Bluenose. The menagerie of MOND theories is something to behold. There's no denying the entertainment value of watching physicists and cosmologists do mental gymnastics trying to deal with the anomalous galactic rotation speeds. Good for them to have something to chew on.  :thumbsup2:

I noticed that the graphics don't add much to the video, and it works pretty well as a podcast. The host is good at what he does, but I'd say he's a natural for podcasts.  ;)

As for the paper, I don't mind admitting the equations are well beyond me, as is a fair part of the text when it begins blending in with the equations. Those with a superior education may make better headway. It seems to have been published in Physical Review Letters, but I found it on arXiv.

"New Relativistic Theory for Modified Newtonian Dynamics" | arXiv

QuoteWe propose a relativistic gravitational theory leading to modified Newtonian dynamics, a paradigm that explains the observed universal galactic acceleration scale and related phenomenology. We discuss phenomenological requirements leading to its construction and demonstrate its agreement with the observed cosmic microwave background and matter power spectra on linear cosmological scales. We show that its action expanded to second order is free of ghost instabilities and discuss its possible embedding in a more fundamental theory.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Bluenose

Quote from: Recusant on November 19, 2021, 03:51:00 AM
Fine stuff, thank you Bluenose. The menagerie of MOND theories is something to behold. There's no denying the entertainment value of watching physicists and cosmologists do mental gymnastics trying to deal with the anomalous galactic rotation speeds. Good for them to have something to chew on.  :thumbsup2:

Tank may recall me sitting in his front room back in 2016 saying that I think we are close to a revolution in physics similar in many ways to that caused by Einstein and Co.  Things like this possible resolution to some pretty big cosmological questions as well as some new thinking about the standard model of sub atomic particals suggest, to me at least, that we are about due to a new revolution.  I suspect that like relativity v Newtonian physics where Newtonian physics has been shown to be basically a special case of relativiy, whatever the new physics ends uo being our current understandings will probably become just special cases that work for most examples but beyond certain limits the new stuff will be required.  I hope I live to see some of this.

Quote
"New Relativistic Theory for Modified Newtonian Dynamics" | arXiv

QuoteWe propose a relativistic gravitational theory leading to modified Newtonian dynamics, a paradigm that explains the observed universal galactic acceleration scale and related phenomenology. We discuss phenomenological requirements leading to its construction and demonstrate its agreement with the observed cosmic microwave background and matter power spectra on linear cosmological scales. We show that its action expanded to second order is free of ghost instabilities and discuss its possible embedding in a more fundamental theory.


Yeah, that's what I thought...   ::)
+++ Divide by cucumber error: please reinstall universe and reboot.  +++

GNU Terry Pratchett


Dark Lightning

I graduated with a B Sc in physics in '83 and started in on a master's in '84. First up was General Relativity, but I made it about 3 weeks and decided I wasn't going to be the one to update Einstein's work.  ::)  I find the general discussion interesting, but I don't want to bash that math into my head at this late age.

hermes2015

Quote from: Dark Lightning on November 19, 2021, 02:53:20 PM
I graduated with a B Sc in physics in '83 and started in on a master's in '84. First up was General Relativity, but I made it about 3 weeks and decided I wasn't going to be the one to update Einstein's work.  ::)  I find the general discussion interesting, but I don't want to bash that math into my head at this late age.

I agree with you. I have a BSc in physics and also in chemistry, but at 75 I would rather solve painting and sculpture problems, and try to improve my knowledge of classical music.
"Eventually everything connects - people, ideas, objects. The quality of the connections is the key to quality per se."
― Charles Eames

Dark Lightning

Quote from: hermes2015 on November 20, 2021, 03:15:56 AM
Quote from: Dark Lightning on November 19, 2021, 02:53:20 PM
I graduated with a B Sc in physics in '83 and started in on a master's in '84. First up was General Relativity, but I made it about 3 weeks and decided I wasn't going to be the one to update Einstein's work.  ::)  I find the general discussion interesting, but I don't want to bash that math into my head at this late age.

I agree with you. I have a BSc in physics and also in chemistry, but at 75 I would rather solve painting and sculpture problems, and try to improve my knowledge of classical music.

:thumbsup: I'm working on carving skills, with a side order of copper smithing. But I haven't hammered any copper in years. I have some sheets that are calling to me. I would rather just appreciate music, though (listening).

billy rubin

Quote from: hermes2015 on November 20, 2021, 03:15:56 AM
Quote from: Dark Lightning on November 19, 2021, 02:53:20 PM
I graduated with a B Sc in physics in '83 and started in on a master's in '84. First up was General Relativity, but I made it about 3 weeks and decided I wasn't going to be the one to update Einstein's work.  ::)  I find the general discussion interesting, but I don't want to bash that math into my head at this late age.

I agree with you. I have a BSc in physics and also in chemistry, but at 75 I would rather solve painting and sculpture problems, and try to improve my knowledge of classical music.

attaboy.

the peoplr who never alter their interests go pretty deep, but nevrr very far.


"I cannot understand the popularity of that kind of music, which is based on repetition. In a civilized society, things don't need to be said more than three times."

Recusant

This hypothesis is nice, and the article says that the large collider that CERN has planned for completion in 2035 may help determine whether there's anything to it.  :hourglass:

"Dark matter could be a cosmic relic from extra dimensions" | Live Science

QuoteDark matter, the elusive substance that accounts for the majority of the mass in the universe, may be made up of massive particles called gravitons that first popped into existence in the first moment after the Big Bang. And these hypothetical particles might be cosmic refugees from extra dimensions, a new theory suggests.

The researchers' calculations hint that these particles could have been created in just the right quantities to explain dark matter, which can only be "seen" through its gravitational pull on ordinary matter. "Massive gravitons are produced by collisions of ordinary particles in the early universe. This process was believed to be too rare for the massive gravitons to be dark matter candidates," study co-author Giacomo Cacciapaglia, a physicist at the University of Lyon in France, told Live Science.

[. . .]

In the team's theory, when gravity propagates through extra dimensions, it materializes in our universe as massive gravitons.

But these particles would interact only weakly with ordinary matter, and only via the force of gravity. This description is eerily similar to what we know about dark matter, which does not interact with light yet has a gravitational influence felt everywhere in the universe. This gravitational influence, for instance, is what prevents galaxies from flying apart.

"The main advantage of massive gravitons as dark matter particles is that they only interact gravitationally, hence they can escape attempts to detect their presence," Cacciapaglia said.

[Continues . . .]

The paper is open access:

"Massive Gravitons as Feebly Interacting Dark Matter Candidates" | Physical Review Letters

"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Bluenose

#8
This article about the measurement of the mass of the W boson by CERN contains this wonderfully understated expression about the fact that the standard model may well be broken "This measurement is in significant tension with the standard model expectation."

The re-organisation of particle physics may well be underway!
+++ Divide by cucumber error: please reinstall universe and reboot.  +++

GNU Terry Pratchett


Ecurb Noselrub

I'll just have to wait for the final conclusion. My background in law does not equip me for playing this game.  I'll be a spectator and utter the occasional "wow!".

Recusant

Quote from: Bluenose on April 12, 2022, 01:53:28 AMThis article about the measurement of the mass of the W boson by CERN contains this wonderfully understated expression about the fact that the standard model may well be broken "This measurement is in significant tension with the standard model expectation."

The re-organisation of particle physics may well be underway!

"Never mind"  ;)

"Shock Boson Result Upending Physics Was a Miscalculation, Scientists Say" | Science Alert

QuoteLast year a new finding in particle physics stunned scientists: a fundamental particle responsible for one of the Universe's four fundamental forces was heavier than predicted.

The discovery of a discrepancy between the W boson's theorized and experimental masses promised new insights beyond the Standard Model, the theoretical blueprint that describes how matter behaves.

Now scientists have run the same numbers again using an updated technique, this time discovering the particle's mass is a close fit with the Standard Model's predictions after all.

While this means we may not need a revolutionary rethink of our current theory of particle physics, we can't but help be a little disappointed. The Standard Model of particle physics remains a hypothetical interpretation of the Universe around us, but so far it has held up well to the battery of tests that we've managed to put it through. At the same time we know there are unexplained gaps: the Standard Model doesn't account for dark matter, for example, or even gravity.

[Continues . . .]

"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Tank

Science at its finest. Damn you science!  ;D
If religions were TV channels atheism is turning the TV off.
"Religion is a culture of faith; science is a culture of doubt." ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett
Remember, your inability to grasp science is not a valid argument against it.

No one

GOP vows to criminalize dark matter.


Recusant

#13
Confounding, this dark matter issue.  :lol:

This story first came out in preprint in Spring of last year. There were probably items about it then, but can't find anything posted here. Now published, apparently, and so an item in one of the pop science places I visit.

The scientists seem somewhat less concerned about these findings than the journalist and headline editor.

"Our Universe Isn't as Clumpy as It Used to Be, And That's a Real Problem" | Science Alert


QuoteA big problem concerning the Universe's dark matter has just grown a little more intense.

Observations of the more recent Universe reveal that this elusive material is distributed differently compared to measures of its spread just after the Big Bang. It appears to be less clumpy now than it was back then – not by much, but enough to suggest that there's something we're missing, and that there may be some sort of fundamental mistake we've made in the standard cosmological model.

It is the latest and one of the most comprehensive in a series of measurements revealing the problem, known as the sigma-eight (S8 tension), detailed in five separate papers in Physical Review D. As yet there is no solution in sight.

"We're still being fairly cautious here," says astrophysicist Michael Strauss of Princeton University.

"We're not saying that we've just discovered that modern cosmology is all wrong. The statistics show that there's only a one in 20 chance that it's just due to chance, which is compelling but not completely definitive. But as we in the astronomy community come to the same conclusion over multiple experiments, as we keep on doing these measurements, perhaps we're finding that it's real."

The discrepancy can be found by looking at different datasets of light from distant Universe, which reveal the distribution of dark matter. One is the cosmic microwave background (CMB). This is the faint background of microwave light that permeates the Universe; leftover radiation from the initial glow that streamed through the Universe a few hundred thousand years after the Big Bang.

The second is 6-years-worth of data from the Hyper Suprime-Cam (HSC) instrument on the Subaru Telescope in Hawaii. The researchers used HSC to conduct what is known as a weak gravitational lensing survey.

[Continues . . .]

The five papers in preprint:

"Hyper Suprime-Cam Year 3 Results: Cosmology from Cosmic Shear Power Spectra"

"Hyper Suprime-Cam Year 3 Results: Cosmology from Cosmic Shear Two-point Correlation Functions"

"Hyper Suprime-Cam Year 3 Results: Measurements of Clustering of SDSS-BOSS Galaxies, Galaxy-Galaxy Lensing and Cosmic Shear"

"Hyper Suprime-Cam Year 3 Results: Cosmology from Galaxy Clustering and Weak Lensing with HSC and SDSS using the Emulator Based Halo Model"

"Hyper Suprime-Cam Year 3 Results: Cosmology from Galaxy Clustering and Weak Lensing with HSC and SDSS using the Minimal Bias Model"
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


zorkan

Time for a rethink.
Seems DM likes to hang out with clusters of galaxies, not just one galaxy.

https://www.bbc.co.uk/news/science-environment-67950749