View Full Version : MOND GR vs. observations?
quasar987
Jul14-07, 04:09 PM
I heard a general theory of relativity was constructed based on MOND rather than on Newton's law of gravitation. How well do the predictions of the MOND GR compare with the classical tests of GR (such as light bending)?
Basically, is it in better or worse agreement with experiment than Newtonian GR?
arivero
Jul14-07, 06:12 PM
A related point is... can MOND adjust for the bullet cluster?
ccdantas
Jul14-07, 06:27 PM
Bekenstein developed the GR version of MOND:
http://arxiv.org/abs/astro-ph/0403694
Can MOND take a bullet?
http://arxiv.org/abs/astro-ph/0606216
All about MOND:
http://arxiv.org/find/grp_cs,grp_math,grp_nlin,grp_physics,grp_q-bio,grp_stat/1/ti:+mond/0/1/0/all/0/1
quasar987
Jul15-07, 12:56 PM
Awesome ccdantas :!!)
Chronos
Jul16-07, 12:12 AM
MOND is not dead, but does appear injured. The bullet cluster does pose a difficult [albeit not insurmountable] problem for the model. The links provided by Christina provide a broad picture of current status.
arivero
Jul16-07, 06:54 AM
Are there other experimental counterexamples (falsations) besides the Bullet cluster?
chrisina
Jul18-07, 09:18 AM
I am still inclined to believe that there must be something really profound behind the "empric" MOND factor a/(a^2 + a0^2)^1/2, especially taking into acount the "coincidence" that the best fit a0 (1.2*10-10 ms-2) is very close to c(lambda/3)^1/2
check :
"MOND as modified inertia" by Milgrom
http://arxiv.org/abs/astro-ph/0510117v1
really, really intriguing, don't you think so, another "numerical coincidence" ?
Chronos
Jul19-07, 01:09 AM
It sounds suspiciously numerological to me chrisina, but, that is strictly my personal perspective - more hunch than reason. The standard model with 'dark' tweaks remains more attractive to me. Remember the atom - it's existence was postulated many centuries before is was cornered in a laboratory.
chrisina
Jul19-07, 04:38 AM
I also prefer the "dark tweaks", (maybe I was influenced by Dark Vador too much when I was a kid... lol).
I am just very puzzled at how the curvature radius of a 4D de Sitter universe specified by the cosmological constant (3/lambda)^1/2 seems to play a very important role for the energy distribution profiles of the individual galaxies.
This requires an explanation.
jgraber
Jul19-07, 06:16 AM
Below is a link to a recent paper about globular clusters discussing evidence favorable to MOND:
http://arxiv.org/ftp/arxiv/papers/0707/0707.2459.pdf
arivero
Aug26-07, 02:48 PM
against mond.
http://arxiv.org/abs/0708.1080
ccdantas
Aug27-07, 08:04 AM
The situation seems to get more and more complicated and interesting. See here:
http://egregium.wordpress.com/2007/08/23/galaxies-and-dark-matter-apart/
Does this fit in with weird and interesting.
from http://www.physicsforums.com/showthread.php?t=181546
"Gaping hole found in universe"
http://arxiv.org/abs/0704.0908
Does this fit in with weird and interesting.
from http://www.physicsforums.com/showthread.php?t=181546
"Gaping hole found in universe"
http://arxiv.org/abs/0704.0908
The MOND effect causes an increase in the gravitational strength at long distances. I suppose that an increase in the long distance gravitational strength could cause all matter to be concentrated in small regions. But I'm just guessing. This is way outside my realm of mediocrity.
Chronos
Aug28-07, 12:52 AM
Garth is a very bright guy. He might be luring you into a serious discussion.
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