Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Light WIMPs, Equivalent Neutrinos, BBN, and the CMB   Recent updates to the observational determinations of the primordial
abundances of helium and deuterium are compared to the predictions of BBN to
infer the universal ratio of baryons to photons (or, the present Universe
baryon mass density parameter Omega_B h^2), as well as to constrain the
effective number of neutrinos (N_eff) and the number of equivalent neutrinos
(Delta N_nu). These BBN results are compared to those derived independently
from the Planck CMB data. In the absence of a light WIMP (chi), N_eff = 3.05(1
+ Delta N_nu/3). In this case, there is excellent agreement between BBN and the
CMB, but the joint fit finds that Delta N_nu = 0.40 +/- 0.17, disfavoring
standard big bang nucleosynthesis (SBBN: Delta N_nu = 0) at 2.4 sigma, as well
as a sterile neutrino (Delta N_nu = 1) at 3.5 sigma. In the presence of a light
WIMP, the relation between N_eff and Delta N_nu depends on the WIMP mass,
leading to degeneracies among N_eff, Delta N_nu, and m_chi. The complementary
and independent BBN and CMB data can break some of these degeneracies.
Depending on the nature of the light WIMP (Majorana or Dirac fermion, real or
complex scalar) the joint BBN + CMB analyses set a lower bound to m_chi in the
range from 0.5 to 5 MeV, and they identify best fit values for m_chi in the
range from 5 to 10 MeV. The joint BBN + CMB analyses find a best fit value for
the number of equivalent neutrinos, Delta N_nu = 0.65, nearly independent of
the nature of the WIMP. The best fit still disfavors the absence of dark
radiation (Delta N_nu = 0 at 95% confidence), while allowing for the presence
of a sterile neutrino (Delta N_nu = 1 at less than 1 sigma). For all cases
considered here, the lithium problem persists. These results, presented at the
2013 Rencontres de l'Observatoire de Paris - ESO Workshop, are based on Nollett
& Steigman 2013 (arXiv:1312.5725 [astro-ph.CO]).

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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: math
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The categories of this paper are: funct-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess