Related papers: Prospects and Limitations for Constraining Light R…
Extremely low metallicity HII regions have been observed with the goal of determining the primordial helium abundance ($Y_{\rm p}$). $Y_{\rm p}$, combined with standard big bang nucleosynthesis and the half-life of the neutron, provides a…
The primordial abundances of deuterium, helium, and lithium probe the baryon density of the universe only a few minutes after the Big Bang. Of these relics from the early universe, deuterium is the baryometer of choice. After reviewing the…
We report the results of a new accurate evaluation of light nuclei yields in primordial nucleosynthesis. All radiative effects, finite nucleon mass, thermal and plasma corrections are included in the proton to neutron conversion rates. The…
The primordial abundances of deuterium and of helium-3, produced during big bang nucleosynthesis, depend sensitively on the baryon density. Thus, the observed abundances of D and \he may provide useful ``baryometers'' provided the evolution…
We examine the possibility that Big Bang Nucleosynthesis (BBN) may produce non-trivial amounts of $^6$Li. If a primordial component of this isotope could be observed, it would provide a new fundamental test of Big-Bang cosmology, as well as…
The primordial abundance of deuterium (D/H) yields a measure of the density of baryons in the universe and is an important complement to determinations from cosmic microwave background (CMB) experiments. Indeed, the current small sample of…
Cosmological bounds on neutrinos and additional hypothetical light thermal relics, such as QCD axions, are currently among the most restrictive ones. These limits mainly rely on Cosmic Microwave Background temperature anisotropies.…
The primordial abundance of 4He, Y_P, is one of the hottest themes in present-day astronomy, mostly due to its cosmological relevance. The disagreement between different determinations has been currently reduced to the 1-2 percent level,…
A cosmic lepton asymmetry $\eta_{\text{l}}=(n_{\text{l}}-n_{\bar{\text{l}}})/n_{\gamma}$ affects the primordial helium abundance and the expansion rate of the early Universe. Both of these effects have an impact on the anisotropies of the…
The synthesis of helium in the early Universe depends on many input parameters, including the value of the gravitational coupling during the period when the nucleosynthesis takes place. We compute the primordial abundance of helium as…
The dissipation effects of primordial magnetic fields on the primordial elemental abundances were investigated. When a magnetic field reconnects, its energy is converted to the kinetic energy of charged particles, as observed for solar…
The relic abundance of baryons - the only form of stable matter whose existence we are certain of - is a crucial parameter for many cosmological processes, as well as material evidence that there is new physics beyond the Standard Model. We…
We investigate constraints on the least explored, smallest mass scales of primordial black holes (PBHs), which evaporate prior to Big Bang Nucleosynthesis (BBN). Our study examines the impact of Planck-mass relics on the allowed fraction of…
Observations of metal-poor extragalactic H II regions allow the determination of the primordial helium abundance, Y_p. The He I emissivities are the foundation of the model of the H II region's emission. Porter, Ferland, Storey, & Detisch…
Many models of new physics including variants of supersymmetry predict metastable long-lived particles that can decay during or after primordial nucleosynthesis, releasing significant amounts of non-thermal energy. The hadronic energy…
Recently we presented a simple method for determining the correlated uncertainties of the light element abundances expected from big bang nucleosynthesis, which avoids the need for lengthy Monte Carlo simulations. We now extend this…
We discuss how measurements of fluctuations in the absorption of cosmic microwave background (CMB) photons by neutral gas during the cosmic dark ages, at redshifts z ~ 7--200, could reveal the primordial deuterium abundance of the Universe.…
Following a brief introduction to early Universe cosmology, the current of status of big bang nucleosynthesis is reviewed and the concordance between theory and observation is examined in detail. The abundances of He4 and Li7 determine the…
We present Keck NIRSPEC and Keck NIRES spectroscopy of sixteen metal-poor galaxies that have pre-existing optical observations. The near-infrared (NIR) spectroscopy specifically targets the HeI 10830A emission line, due to its sensitivity…
The role of the dilaton field and its coupling to matter may result to a dilution of Dark Matter (DM) relic densities. This is to be contrasted with quintessence scenarios in which relic densities are augmented, due to modification of the…