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

Posted: August 31 2005
by Fergus Simpson
This paper certainly makes some big claims! Would be interested to hear the thoughts of anyone working in this area....

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

Posted: August 31 2005
by Simon DeDeo
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?

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

Posted: September 01 2005
by Gil Holder
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.