Weinberg's dark matter idea re fractional cosmic neutrinos

[marcus]

Weinberg's dark matter idea re "fractional cosmic neutrinos"

http://arxiv.org/pdf/1305.1971v1.pdf
http://arxiv.org/abs/1305.1971
Goldstone Bosons as Fractional Cosmic Neutrinos
Steven Weinberg
(Submitted on 8 May 2013)
It is suggested that Goldstone bosons may be masquerading as fractional cosmic neutrinos, contributing about 0.39 to what is reported as the effective number of neutrino types in the era before recombination. The broken symmetry associated with these Goldstone bosons is further speculated to be the conservation of the particles of dark matter.
9 pages

 

[mitchell porter]

He should have called it "The First 3.39 Neutrinos".

 

[marcus]

But how do you like the paper? I posted notice of it particularly because I was interested to learn your reaction to the idea, and those of a few others.

 

[ohwilleke]

I like his mode of reasoning, leaping from one reasonable assumption to the next and using approximate order of magnitude estimates to narrow the parameter space. And, the case for Neff being associated with a fractional neutrino species is favored by the data.

On the other hand, it ends with a fizzle instead of a bang, and it is hard to know if there is a way to elaborate the idea further to see if it really makes sense.

 

[mitchell porter]

But how do you like the paper?

The idea goes on the list of possibilities. Many models now suppose that dark matter has dark interactions of its own, new forces which only it feels, and some of them might in future incorporate Weinberg's idea as an explanation of Neff, depending on how well it fits.

That the goldstone mass has to have just the right order of magnitude (equation 9) for this to work, might be regarded as a point against the idea. This is also a characteristic shortcoming of all the "minimal" BSM theories - they freely employ finetuning of parameters, in order to squeeze all the required new physics into a minimal extension of the SM. Still, that exercise tends to be instructive, and turns up ideas which could be used in a larger, more relaxed model.