Loeb Weiner YIDM Yukawa-Interacting Dark Matter particle

[marcus]

Loeb at Harvard is a top cosmologist. For six years or so I've seen him come out with paper after paper that seemed unusually insightful over a broad range of topics. He and Neal Weiner (Princeton IAS) just posted a creative idea about DM,

http://arxiv.org/abs/1011.6374

about how some minor puzzles or "tensions" in cosmology (such as the distributiion of DM in dwarf galaxies, compared to its density distribution in larger galaxies) could be resolved by supposing that dark matter WIMPs (weakly interacting massive particles) were able to interact according to a special force---which they dub a "dark force".

This is a speculative idea. Probably 95% of ideas that are speculative like this fail. We can't jump to the conclusion that it is right. They don't say it is right---they just propose it as something to check out and consider.

The conjectured DM particle they have christened with the name YIDM (Yukawa-Interacting Dark Matter particle).

MTd2 voiced an idea here about DM and a Yukawa potential. I don't remember exactly when---I think it was in the past couple of years. So that's a nice coincidence. There could be some overlap. Also there have been a number of papers speculating about what kind of (weak-ish) interaction there could be between DMs or between DMs and ordinary. This Loeb Weiner paper is certainly not the first!

But what they do that I found so interesting (when MTd2 kindly pointed the paper out to me) is they USE the idea to resolve some minor little discrepancies---things most of us haven't even heard of---in the standard cosmo model. Mismatches where they do computer simulations of the formation of large and small galaxies---and determine by simulation what the DM clouds should look like---and then compare with the actual observed DM clouds and density maps---and get some discrepancies, which Loeb Weiner describe and address.

So they are coming at it from an observational cosmology viewpoint (not from a particle theory viewpoint) and inferring particle properties like an interaction potential from the observation evidence.

I guess I sound mildly excited. I am mildly excited. Hopefully somebody here will be prepared to comment and shed some light on the paper. Thanks to MTd2 for pointing it out!

 

[marcus]

In case anyone is interested and wants to check it out, here is the abstract:

http://arxiv.org/abs/1011.6374
Cores in Dwarf Galaxies from Dark Matter with a Yukawa Potential
Abraham Loeb, Neal Weiner
6 pages, 2 figures
(Submitted on 29 Nov 2010)
"We show that cold dark matter particles interacting through a Yukawa potential could naturally explain the recently observed cores in dwarf galaxies without affecting the dynamics of objects with a much larger velocity dispersion, such as clusters of galaxies. The velocity dependence of the associated cross-section as well as the possible exothermic nature of the interaction alleviates earlier concerns about strongly interacting dark matter. Dark matter evaporation in low-mass objects might explain the observed deficit of satellite galaxies in the Milky Way halo and have important implications for the first galaxies and reionization."

What they mean by a "core" later in the paper has a low broad bump in density as opposed to a sharper cusp or spike.

==sample excerpt from page 1==
The collisionless cold dark matter (CDM) model has been highly successful in accounting for the gravitational growth of density perturbations from their small observed amplitude at early cosmic times (as imprinted on the cosmic microwave background anisotropies [1]) to the present-day structure of the Universe on large scales. However, it is far from clear that
the predictions of this model are valid on small scales.

New data on low mass galaxies indicate that their dark matter distribution has a core [2], in contrast to the cusped profile expected from collisionless CDM simulations [3]. The mean value of the inner logarithmic slope of the mass density profile in seven dwarf galaxies within the THINGS survey is observed to be −0.29 ± 0.07 [4], much shallower than the expected slope of ∼ −1 from pure CDM simulations.

Moreover, the dynamics of dwarf spheroidal galaxies, such as Fornax [5], Ursa-Minor [6], and Sculptor [7], whose luminosities and dynamical masses are smaller by 2-3 orders of magnitude than the THINGS galaxies, indicates a characteristic core density of ... Since these dwarf spheroidals are dominated by dark matter throughout, it is challenging to explain their inferred cores by the gravitational interaction of the dark matter with the baryons [8].
...
...
Recently, there has been growing interest in the possibility that WIMPs exhibit “dark forces” as a means to address a wide range of anomalies [22]. In particular, it was realized that a new force carrier φ (scalar or vector) might naturally mediate a long-range interaction...
==endquote==

 

[MTd2]

Marcus, my proposal on my private communication with you it is that matter and dark matter are different because they have a kind of color, like the strong force. It might or not be associated to gravity. Something related here:

http://xxx.lanl.gov/abs/0901.4005

Implications of Graviton-Graviton Interaction to Dark Matter

A. Deur
(Submitted on 26 Jan 2009 (v1), last revised 6 May 2009 (this version, v2))
Our present understanding of the universe requires the existence of dark matter and dark energy. We describe here a natural mechanism that could make exotic dark matter and possibly dark energy unnecessary. Graviton-graviton interactions increase the gravitational binding of matter. This increase, for large massive systems such as galaxies, may be large enough to make exotic dark matter superfluous. Within a weak field approximation we compute the effect on the rotation curves of galaxies and find the correct magnitude and distribution without need for arbitrary parameters or additional exotic particles. The Tully-Fisher relation also emerges naturally from this framework. The computations are further applied to galaxy clusters.

http://xxx.lanl.gov/abs/astro-ph/0309474

Non-Abelian Effects in Gravitation

A. Deur
(Submitted on 17 Sep 2003)
The non-abelian symmetry of a lagrangian invalidates the principle of superposition for the field described by this lagrangian. A consequence in QCD is that non-linear effects occur, resulting in the quark-quark linear potential that explains the quark confinement, the quarkonia spectra or the Regge trajectories. Following a parallel between QCD and gravitation, we suggest that these non-linear effects should create an additional logarithmic potential in the classical Newtonian description of gravity. The modified potential may account for the rotation curve of galaxies and other problems, without requiring dark matter.

 

[MTd2]

Quoting from the paper posted by marcus:

Page 2:

"Scattering through a massive mediator is equivalent to having a Yukawa potential. The elastic scattering problem is then analogous to the screened Coulomb scattering in a plasma [29], which is well t by a cross-section [24, 30]" [follows equation 1]

http://xxx.lanl.gov/PS_cache/arxiv/pdf/1011/1011.6374v1.pdf

Which leads to this:

A great evolutionary geneticists of the 20th century published 2 papers on the origin of Dark Matter:

http://en.wikipedia.org/wiki/Roy_John_Brittenhttp://authors.library.caltech.edu/9...BRIpnas98a.pdf
http://www.ncbi.nlm.nih.gov/pmc/arti...01083-0426.pdf

Both were published on PNAS, but are really unknown. It supposes that an unknown agent scatters gravity creating a kind of screaning effect.

 

[MTd2]

I am becoming convinced that DM does not exist. It is all just GR. The Yukawa potential, with a fictional mass, is found on Deur's paper.