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New paper about No Dark Matter 
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#1
Dec904, 07:32 PM

Astronomy
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PF Gold
P: 23,102

Gravitational Theory, Galaxy Rotation Curves and Cosmology without Dark Matter
J. W. Moffat http://arxiv.org/abs/astroph/0412195 "Einstein gravity coupled to a massive skew symmetric field [tex]F_{\mu\nu\lambda}[/tex] leads to an acceleration law that modifies the Newtonian law of attraction between particles. We use a framework of nonperturbative renormalization group equations as well as observational input to characterize special renormalization group trajectories to allow for the running of the effective gravitational coupling G and the coupling of the skew field to matter. The latter lead to an increase of Newton's constant at large galactic and cosmological distances. For weak fields a fit to the flat rotation curves of galaxies is obtained in terms of the mass (masstolight ratio M/L) of galaxies. The fits assume that the galaxies are not dominated by exotic dark matter and that the effective gravitational constant G runs with distance scale. The equations of motion for test particles yield predictions for the solar system and the binary pulsar PSR 1913+16 that agree with the observations. The gravitational lensing of clusters of galaxies can be explained without exotic dark matter. An FLRW cosmological model with an effective G=G(t) running with time can lead to consistent fits to cosmological data without assuming the existence of exotic cold dark matter." 31 pages, 20 figures many of the figures show galaxy rotation curve fits 


#2
Dec904, 08:18 PM

PF Gold
P: 7,363

I will turn you to the dark side of the force (polarized ZPE fields as the source of gravitation and inertia). I truly wish I had the math skills to express the effects I see in my thought experiments with this model. As a VERY crude analogy, imagine a bunch of little bar magnets thrown on a slippery table top. They will immediately clump in a way that represents the lowest potential energy state acheivable from that initial state. (less suspense, more closure, in a sociological analogy) I believe the ZPE fields do this as well, and the attraction expressed in the binding of the lowest potential energy state is what we call gravity.



#3
Dec1004, 02:22 AM

Sci Advisor
PF Gold
P: 9,366

I'm not comfortable with Moffat's explanation. Unless I made an OOM error, the effects he describes would have measurable effects on planetary orbits within our solar system. Futhermore, I do not see how it addresses the resulting flatness problem of spacetime curvature.



#4
Dec1004, 10:10 AM

P: 108

New paper about No Dark Matter
I cannot claim to understand this paper, but it appears that G=Go within the solar system but runs up to G=6Go at larger scales, so that planet trajectories are not affected, but the amount of dark matter is replaced by a variable G.
So it appears that the introduction of variability in distance and time to the gravitational constant plus nonsymetric gravity theory can fit all observed phenomena including a flat spacetime curvature and gravitational lensing. So my question is, what gives us the right to make G variable? Is it not possible that the variable G is just a curve fit to actual Dark Matter. Is there some other process that could make G variable. Is there some way to observe if that is true. Is the theory falsifiable or just a model? I quess that Occums razor applies. Both invisible energy and matter, and a variable G, can explain the data. But invisibility is preferred to variability. Richard 


#5
Dec1004, 06:57 PM

Sci Advisor
PF Gold
P: 9,366

Agreed yanniru. It does appear local solar system dynamics are not distinguishable from GR predictions under the NGT model. I'm curious why no mention was made of the pioneer anomaly. It was also unclear how combining GR with a skew symmetric rank 3 tensor field invoking a 'fifth force' coupling constant produces a simpler gravitational theory. The variance of G over time was intriguing, yet unexplained. G is initially low and remains constant for about 10,000 years, then suddenly climbs to the present, much higher value by the time the universe is 1,000,000 years old. The absence of an explanation for this phenomenon, it looks like hand tuning to get a .04 baryonic density in the primordial universe and a .24 baryonic density after 1,000,000 years. That was a bit hard to swallow.



#6
Dec1204, 11:22 PM

P: 631

When the current theory has issues, everything is on the table.
Invisible matter in and of itself, isn't much of a theoretical stretch. Requiring 80%+ of all matter in the universe to be nonbaryonic, despite the fact that there is not yet a single direct observation of nonbaryonic matter, is a stretch. If the stuff makes up so much of all matter, one needs a pretty good reason for explaining why no one has ever come across a chunk of the stuff. Moffat, Mannheim, and MilgromBekenstein all illustate that it is possible to devise modifications of GR and more specifically of gravity, which eliminate the vast majority of the implication of dark matter. Indeed, there are at least three similar, but not identical ways, to do so. Moreover, these M^3 scholars also illustrate an additional limitation on any viable CDM theory. Not only must it find nonbaryonic matter not yet observed to account for the vast majority of the matter in the universe, it most also explain why the distribution of that matter is so tightly fine tuned to the visible light in the galaxies observed, so as to fit M^3 predictions. In a CDM context, this has to be done more or less entirely through the galaxy formation process, as CDM interacts only through standard GR gravity. A satisfactory and coherent theory to explain the incredible coincidence of galaxy formation that distributed CDM in this way has not emerged to my knowledge. A G constant that runs with time is certainly the most worrisome aspect of the Moffat approach, but there is a very well documented phenomena out there and CDM as a solution has serious issues. 


#7
Dec1304, 06:31 AM

PF Gold
P: 7,363




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