[astro-ph/0508572] Observational Evidence for Extra Dimensions from Dark Matter

Authors:  Bo Qin, Ue-Li Pen, Joseph Silk
Abstract:  Recent astronomical observations of systems of dark matter, which have been cited as providing possible support for self-interacting cold dark matter, may provide evidence for the extra dimensions predicted by superstring scenarios. We find that the properties of the required dark matter self-interaction are precisely the consequences of a world with 3 large extra dimensions of size \~1nm, where gravity follows the r^{-5} law at scales below ~1nm. From the cross sections measured for various dark matter systems, we also constrain the mass of dark matter particles to be m_x ~ 3*10^{-16} proton mass, consistent with the mass of axions.
[PDF]  [PS]  [BibTex]  [Bookmark]

Discussion related to specific recent arXiv papers
Post Reply
Fergus Simpson
Posts: 27
Joined: September 25 2004
Affiliation: University of Barcelona

[astro-ph/0508572] Observational Evidence for Extra Dimensio

Post by Fergus Simpson » August 31 2005

This paper certainly makes some big claims! Would be interested to hear the thoughts of anyone working in this area....

Simon DeDeo
Posts: 44
Joined: October 26 2004
Affiliation: Santa Fe Institute

[astro-ph/0508572] Observational Evidence for Extra Dimensio

Post by Simon DeDeo » August 31 2005

It is a fun paper to read (just skimming it now.) I am curious -- how well established is the problem of "missing power"; one would imagine, for example, that baryons would act to smudge out what would otherwise be cuspy profiles on small scales without the need for an additional collisional component to the CDM self-interaction.

How well do we understand CDM+baryon systems? Any simulation gurus out there want to weigh in?

Gil Holder
Posts: 27
Joined: September 25 2004
Affiliation: McGill University

[astro-ph/0508572] Observational Evidence for Extra Dimensio

Post by Gil Holder » September 01 2005

One of my colleagues here (Guy Moore) pointed out that the deBroglie wavelength is not only much bigger than the scattering length, as they point out, but is also much larger than the mean interparticle spacing. That would seem to indicate that treating this as one particle scattering off another is a bit simplistic, at best.

Roughly, the deBrogile wavelength should be order km, and the mean interparticle spacing must be of order sub-um near the galactic center. The effective graininess should be reduced by having of order 10^{30} particles per deBrogilie wavelength.

To quote Guy:
this is the reason that light does not scatter appreciably in going
through a liquid or a glass;

this is why neutrinos and (perhaps) CDM particles can scatter coherently
from nuclei, rather than nucleon by nucleon;

it is why long wavelength phonons are ballistic in an amorphous medium,
but short wavelength phonons move diffusively.
Seems like a pretty good argument to me.

Post Reply