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Big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) are two major pillars of cosmology. Standard BBN accurately predicts the primordial light element abundances ($^4$He, D, $^3$He and $^7$Li), depending on one parameter, the baryon density. Light element observations are used as a baryometers. The CMB anisotropies also contain information about the content of the universe which allows an important consistency check on the Big Bang model. In addition CMB observations now have sufficient accuracy to not only determine the total baryon density, but also resolve its principal constituents, H and $^4$He. We present a global analysis of all recent CMB data, with special emphasis on the concordance with BBN theory and light element observations. We find $Omega_{B}h^{2}=0.025+0.0019-0.0026$ and $Y_{p}=0.250+0.010-0.014$ (fraction of baryon mass as $^4$He) using CMB data alone, in agreement with $^4$He abundance observations. With this concordance established we show that the inclusion of BBN theory priors significantly reduces the volume of parameter space. In this case, we find $Omega_{B}h^2=0.0244+0.00137-0.00284$ and $Y_p = 0.2493+0.0006-0.001$. We also find that the inclusion of deuterium abundance observations reduces the $Y_p$ and $Omega_{B}h^2$ ranges by a factor of $sim $2. Further light element observations and CMB anisotropy experiments will refine this concordance and sharpen BBN and the CMB as tools for precision cosmology.
We report the results of a detailed calculation of nucleon weak interactions relevant for the neutron to proton density ratio at the onset of primordial nucleosynthesis. Radiative electromagnetic corrections, finite nucleon mass terms, thermal radiat
Future arcminute resolution polarization data from ground-based Cosmic Microwave Background (CMB) observations can be used to estimate the contribution to the temperature power spectrum from the primary anisotropies and to uncover the signature of re
We have measured the Balmer-series x-rays of kaonic $^4$He atoms using novel large-area silicon drift x-ray detectors in order to study the low-energy $bar{K}$-nucleus strong interaction. The energy of the $3d to 2p$ transition was determined to be 6
We report a 0.08 % measurement of the bound neutron scattering length of $^4$He using neutron interferometry. The result is $b = (3.0982 pm 0.0021 mbox{ [stat]} pm 0.0014 mbox{ [sys]}) mbox{ fm}$. The corresponding free atomic scattering length is $a
We constrain the possible time variation of the Higgs vacuum expectation value ($v$) by recent results on the primordial $^4$He abundance ($Y_P$). For that, we improve the analytic models of the key-processes in our previous analytic calculation of t