Another dark horse in the MOND race

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In summary: Looks like they're looking at theories that have extra gravitational scalars that become heavy near any mass source.This looks like a good contribution to the Rencontres de Moriond.
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marcus
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Another "dark" horse in the MOND race

I'm glad there are several competing alternatives to dark matter.
Bekenstein's TeVeS doesn't have the field to itself.
this appeared today:

http://arxiv.org/abs/astro-ph/0605322
Dark energy, MOND and sub-millimeter tests of gravity
I. Navarro, K. Van Acoleyen
6 pages, to appear in proceedings of the 51st Rencontres de Moriond

"We consider modifications of General Relativity obtained by adding the logarithm of some curvature invariants to the Einstein-Hilbert action. These non-linear actions can explain the late-time acceleration of the universe giving an expansion history that differs from that of a pure cosmological constant. We show that they also modify the Newtonian potential below a fixed acceleration scale given by the late-time Hubble constant times the speed of light. This is exactly what is required in MOND, a phenomenological modification of the Newtonian potential that is capable of explaining galactic rotation curves without the need to introduce dark matter. We show that this kind of modification also predicts short distance deviations of Newton's law at the sub-mm scale and an anomalous shift in the precession of the Moon's orbit around the Earth, both effects of a size that is less than an order of magnitude below current bounds."

Ignacio Navarro is at Cambridge----basically the same bunch as Daniele Oriti: the DAMPT

Navarro and van Acoleyen have a bid to

1. replace Lambda or dark energy
2. replace dark matter and get a better fit to the rotation curves
3. achieve rapid testability---falsification attainable with only a factor of 10 improvement in the accuracy of measurements that are already made

sounds good. the kind of thing it is nice when theorists come up with.

maybe it will be shot down. and maybe not. if it is not then I would guess that someone at
Perimeter will try ways to wangle those effects using a more fundamental model of spacetime
 
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  • #2
It's all bells and whistles to me when I hear

"galactic rotation curves without the need to introduce dark matter"

I think that is fundamentally wrong. Just another short sighted explanation that conveniently ignores the preponderance of observational evidence.
 
  • #3
Preponderance of evidence?

Chronos said:
It's all bells and whistles to me when I hear

"galactic rotation curves without the need to introduce dark matter"

I think that is fundamentally wrong. Just another short sighted explanation that conveniently ignores the preponderance of observational evidence.

Exactly what, in your view, is this preponderance of observational evidence?

And how is it related/not related to galactic rotation curves?

TIA

Jim Graber
 
  • #4
Virial theorem, lensing and stuff like that.
 
  • #5
a second post by Navarro and friend in as many days

http://arxiv.org/abs/gr-qc/0605091
Long distance modifications of gravity in four dimensions
I. Navarro, K. Van Acoleyen
4 pages, contribution to the proceedings of the Rencontres de Moriond: Contents and Structures of the Universe, March 18-25, 2006, La Thuile


"We discuss some general characteristics of modifications of the 4D Einstein-Hilbert action that become important for low space-time curvatures. In particular we focus on the chameleon-like behaviour of the massive gravitational degrees of freedom. Generically there is at least one extra scalar that is light on cosmic scales, but for certain models it becomes heavy close to any mass source."
 

FAQ: Another dark horse in the MOND race

What is the "MOND race" and why is it important?

The MOND race refers to the ongoing scientific debate surrounding the Modified Newtonian Dynamics (MOND) theory, which proposes an alternative explanation for the observed discrepancies in the rotation curves of galaxies. This theory is important because it challenges the widely accepted theory of dark matter and has the potential to revolutionize our understanding of the universe.

How does the "dark horse" theory differ from the traditional dark matter theory?

The "dark horse" theory, also known as the MOND theory, differs from the traditional dark matter theory in that it suggests that the observed discrepancies in the rotation curves of galaxies can be explained by modifying the laws of gravity rather than the presence of invisible matter. This theory proposes that gravity behaves differently on large scales, which can account for the observed phenomena without the need for dark matter.

What evidence supports the "dark horse" theory in the MOND race?

Support for the MOND theory comes from various observations, such as the flat rotation curves of galaxies, the observed mass discrepancies in galaxy clusters, and the overall distribution of matter in the universe. Additionally, simulations based on the MOND theory have been able to reproduce many of the observed features of galaxy dynamics.

What are the main criticisms of the "dark horse" theory?

One of the main criticisms of the MOND theory is that it does not fully explain all the observed phenomena, such as the gravitational lensing effects seen in galaxy clusters. Additionally, some scientists argue that modifying the laws of gravity on large scales is not supported by the current understanding of physics. The MOND theory also faces the challenge of explaining the observed distribution of matter in the early universe.

What are the implications of the "dark horse" theory for our understanding of the universe?

If the MOND theory is confirmed, it would have significant implications for our understanding of the universe. It would challenge the existence of dark matter, which makes up a large portion of the known universe, and would require a rethinking of our current understanding of gravity. It could also potentially lead to a better understanding of the nature of space and time, as well as the evolution of the universe as a whole.

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