[astro-ph/0412066] Indication for Primordial Anisotropies in the Neutrino Background from WMAP and SDSS

Authors:  Roberto Trotta (U. Geneva), Alessandro Melchiorri (Rome U.)
Abstract:  We demonstrate that combining Cosmic Microwave Background anisotropy measurements from the 1st year WMAP observations with clustering data from the SLOAN galaxy redshift survey yields an indication for primordial anisotropies in the cosmological Neutrino Background.
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Discussion related to specific recent arXiv papers
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Anze Slosar
Posts: 183
Joined: September 24 2004
Affiliation: Brookhaven National Laboratory

[astro-ph/0412066] Indication for Primordial Anisotropies in

Post by Anze Slosar » December 03 2004

Authors in these papers vary one of the parameters fixed by the standard theory, namelly c_vis^2 which equals to 1/3 in the standard theory, but the value of 0 would mean no anisotropies in neutrino background...

Very interesting! I would like to know, why plot of probablity of c^2 marginalised over everything isn't included? I'd like to see it all the way up to c^2=1 (I know you say that it "doesn't produce any relevant constraint), but it would still be interesting to see where it peaks... Judging from fig2 it seems it probably peaks above 0.3... Any commets, Alessandro?

Alessandro Melchiorri
Posts: 122
Joined: September 24 2004
Affiliation: University of Rome

[astro-ph/0412066] Indication for Primordial Anisotropies in

Post by Alessandro Melchiorri » December 03 2004

Hi Anze,
Thanks for your nice comments ! Yes you are right, we should include also a Figure with the countours up to 1. It indeed peaks for higher values of 1/3 but not in such a relevant way to exclude c_vis=0.333 (is quite flat). Since the motivations for c_vis=1 are not clear or a bit too exotic (at least to us) we put the prior c_vis<0.34. Higher values of c_vis would have excluded c_vis=0 even more (which is the point of our paper) but if you don't have a clear physical motivation for it, this can bias your result.


Scott Dodelson
Posts: 13
Joined: October 06 2004
Affiliation: Fermilab/U. Chicago

[astro-ph/0412066] Indication for Primordial Anisotropies in

Post by Scott Dodelson » December 05 2004

It would be interesting to see the likelihood contours in [tex]N_\nu-c_s[/tex] plane. The standard model result (3-1/3) probably falls well within the allowed region. But how well can we do in the future [e.g. with weak lensing]? It would also be interesting to see how complementary CMB and LSS constraints are in this plane. Of course this bears on the question of whether or not the CNB can ever be detected. I seem to remember some papers on this, but I don't think ever with this 2D plane as the battleground.

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