Is dark matter real?

Chipper Q
Chipper Q
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Thanks, Ben. I took to heart

Thanks, Ben. I took to heart what you said earlier about the value of the simpler picture, but I realize it's not that simple. And rather than confusion, it was more like one 'Eureka!' after another, reading about some of the fascinating properties of SFHe (e.g., in the lab, with it right in front of you, bits of styrofoam have to be used just to see where the surface of the liquid actually is). I have a lot more to learn, then, about the way various pieces of the cosmological puzzle fit together, and so thanks (also to Solomon, Mike, and the otheres) for the help!

Chipper Q
Chipper Q
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RE: ( edit ) Chipper,

Message 38363 in response to message 38342

Quote:
( edit ) Chipper, there's a good discussion of the awesome properties of Helium, in various forms, as used for the Large Hadron Collider here. Go to the talk by L.Evans "The LHC" - it has a nifty overview of their magnetic arrangements too. I was stunned to discover the stored energy in the beam, when fully operational, will be of the order of 80 kilos of TNT! The Helium, and other systems have to withstand any accidental sudden quenching of that... phew!


Maybe a dumb question, as I'm trying to understand several things regarding parton distribution functions, particle collisions, cosmic rays, etc., at the same time:

Are the muons, mesons, neutrinos, and WIMPs(!) from cosmic rays taken into account with regard to what's required to maintain the beams in storage rings? So far I've seen 'quantum fluctuations', 'bremmstralung', and 'various other processes' listed as reasons for beam degradation. The reason I ask is because it seems like there would be many more 'events' to observe if the detector material is moving fast enough (opposed to stationary detector material, where probabilities for events are measured in a few hundred per year, if at all).

It seems like the beams in the LIGO detectors would contend with the same shower of particles - could useful data come from the 'mode cleaner' portion of the detector?

Mike Hewson
Mike Hewson
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RE: Maybe a dumb question,

Message 38364 in response to message 38363

Quote:

Maybe a dumb question, as I'm trying to understand several things regarding parton distribution functions, particle collisions, cosmic rays, etc., at the same time:

Are the muons, mesons, neutrinos, and WIMPs(!) from cosmic rays taken into account with regard to what's required to maintain the beams in storage rings?


For maintainence of the beam, not to my knowledge. But for the detectors they'd need to distinguish between events arising from the collisions that they set up vs. stray stuff entering from outside.

Quote:
So far I've seen 'quantum fluctuations', 'bremmstralung', and 'various other processes' listed as reasons for beam degradation.


The 'quantum fluctuations' refer to the fact that one can never be precisely sure of the state of the beam particles - Heisenberg Uncertainty etc - so with travel around the ring the beams need continual 'shepherding' to bring the groups of particles to the collision vertices is a 'known' condition.
'Bremmstralung' literally means 'braking radiation' and was first described in the context of firing electrons at lumps of heavy metals. An energetic electron would plough through an electron cloud around the nucleus and often descend deep into the Coulomb well of the nucleus, swing around the nucleus ( like a comet around the Sun, but faster! ) and fire back out in some other direction. However during that change of direction photons of high energy would be emitted ( generally along the original line of approach ), this indeed generates radiation in the X-ray band of frequency. Variations on this scenario are used daily for radiology. You need kilovolt potentials to accelerate/energise the electrons and some heavy nuclei to 'brake' them.

Quote:
The reason I ask is because it seems like there would be many more 'events' to observe if the detector material is moving fast enough (opposed to stationary detector material, where probabilities for events are measured in a few hundred per year, if at all).


I guess so ...... you get wetter if you run into the rain! :-)

Quote:
It seems like the beams in the LIGO detectors would contend with the same shower of particles - could useful data come from the 'mode cleaner' portion of the detector?


No, and no, I'd say. To my knowledge the photons at the frequency produced by the CO2 lasers in LIGOs doesn't interact much with cosmic rays.

Cheers, Mike.

( edit ) I've discovered this paper, which refers to bremsstrahlung gravitational-wave radiation. This sounds very similiar to the electron/nuclear interaction I described above, but clearly applies to close encounters between stars in say a globular cluster!! Weird huh?

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Joachim Schmidt
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RE: Are the muons, mesons,

Message 38365 in response to message 38363

Quote:

Are the muons, mesons, neutrinos, and WIMPs(!) from cosmic rays taken into account with regard to what's required to maintain the beams in storage rings?

No, they aren't. The beams get accelerated by dipolmagnets, and get stabilized by quadrupol- and sixtupolmagnets. They dont' care for cosmic rays hitting the storage ring.
In the detectors, there are muon chambers to detect muons whether from beam-beam collisions or from cosmic rays. By analyzing the signals from the detector you can easily decide if this were cosmic muons or muons from a Higgs decay.

greets

Chipper Q
Chipper Q
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Thanks, Mike. While watching

Thanks, Mike. While watching the first day's lectures (re: the LHC), I had to google DGLAP equations for some background; fascinating how valuable MC simulations can be, not only to check the models, but also to improve them. As programs are being converted from Fortran to C++, in an effort to have next-to-NLO equations ready for evaluation by the time the LHC goes online, I was wondering why there isn't a program written that would generate all the necessary routines for each possible interaction – a program to write the programs. I'm guessing, but if all the basic rules were written down in concise, abbreviated statements, then it should look an awful lot like XML, so then routines for any and all interactions, along with their data and pertinent calculations, could easily be compiled from the XML blueprint...

Quote:
Quote:
The reason I ask is because it seems like there would be many more 'events' to observe if the detector material is moving fast enough (opposed to stationary detector material, where probabilities for events are measured in a few hundred per year, if at all).

I guess so ...... you get wetter if you run into the rain! :-)


That's what I was thinking, and I thought the fastest moving material there is can be found in ion beams. So the ion beams should cast a really good shadow? I'm looking forward to the lectures on the LHC detectors (as time permits).

Thanks, Joachim, and Mike, I missed your edit re: the bGWr paper; I'll check it this evening...

Chipper Q
Chipper Q
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RE: ( edit ) I've

Message 38367 in response to message 38364

Quote:
( edit ) I've discovered this paper, which refers to bremsstrahlung gravitational-wave radiation. This sounds very similiar to the electron/nuclear interaction I described above, but clearly applies to close encounters between stars in say a globular cluster!! Weird huh?


Hmm, this paper considers possibilities for observing gravitational bremsstrahlung signals (GBS) in a single group of objects (galaxies, and globular clusters), but what about for some of the galactic merger models?

Isn't the good ol' gravitational wave radiation from NS/NS, NS/BH, and BH/BH mergers also technically the same kind of bremsstrahlung, but with a chirped waveform?

ronalds8
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well something obviously has

well something obviously has to be there, to explaine all the weird fenomenon, what the dark matter exactly is , thats another question. I dont see a problem that we havent fount dark matter on earth or near it, if you live on inland and havent seen the ocean , it doesnt mean that it doesent exist.

@nne
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RE: well something

Message 38369 in response to message 38368

Quote:
well something obviously has to be there, to explaine all the weird fenomenon, what the dark matter exactly is , thats another question. I dont see a problem that we havent fount dark matter on earth or near it, if you live on inland and havent seen the ocean , it doesnt mean that it doesent exist.

i've heard that an interaction between dark matter and matter had been recently observed during a collision between two galaxies.

It was added that this dark matter could be of a different composition compared to the "usual" matter and that it could go through everything that goes in its way.

Have you heard about this and do you have any comment ?

gravitonring
gravitonring
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these aether unit guys eat

Message 38370 in response to message 38369

these aether unit guys eat rather well it seems :)

there seems to be dark matter in my body weight...

nothing that i do will make it lose its gravity :)

http://www.quantumaetherdynamics.com/aether.html
The Aether Physics Model and Superstring theory

Graviton Ring ... G R

Gene Roddenberry ... G R

maybe this is an omen

everything is true, the opposite of everything is also true

Chipper Q
Chipper Q
Joined: 20 Feb 05
Posts: 1,540
Credit: 708,571
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RE: RE: well something

Message 38371 in response to message 38369

Quote:
Quote:
well something obviously has to be there, to explaine all the weird fenomenon, what the dark matter exactly is , thats another question. I dont see a problem that we havent fount dark matter on earth or near it, if you live on inland and havent seen the ocean , it doesnt mean that it doesent exist.

i've heard that an interaction between dark matter and matter had been recently observed during a collision between two galaxies.

It was added that this dark matter could be of a different composition compared to the "usual" matter and that it could go through everything that goes in its way.

Have you heard about this and do you have any comment ?


There was this article (back in August): Cosmic collision reveals dark matter
Comments: seems quite conclusive (re: modified theories on gravity), and there should be more examples that show the same effect (separation of the dark matter from normal matter during galactic merger), but since it takes more than one instrument (ie, optical and x-ray instruments) to get the composite image, and then additional observations and calculations to determine where the gravitational lensing is occurring, I'm guessing we'll have to wait a while... effectively reducing the rest of my comments, at the moment, to an enthusiastic "Hmmm...." :)

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