36572119
Radiative decays of massive relic particles and the submillimeter background.
We consider the interaction of the decay photons of an unstable relic particle species with the microwave background radiation. The radiative decays of these particles delay recombination and serve as an energy source for the resultant plasma. Nonrelativistic Compton scattering by these electrons couples the decay photons to the microwave background, producing submillimeter distortions. If the decay products close the Universe, they must decay with a radiative branching ratio larger than 2.5/times/10/sup /minus/5/ in order to produce recently observed excess submillimeter background radiation. To be consistent with measurements of the uv background, their mass /ital m//much gt/114 keV and their decay redshift /ital Z//sub /ital d///much gt/5200.
18626728
Testing Two Nuclear Physics Approximations Used in the Standard Leaky-Box Model for the Spallogenic Production of LiBeB
The spallative production rates of lithium, beryllium, and boron (LiBeB) are a necessary component in any calculation of the evolution of these nuclei in the Galaxy. Previous calculations of these rates relied on two assumptions relating to the nuclear physics aspects: the straight-ahead approximation that describes the distribution of fragment energies and the assumption that the major contributor to the production rate arises from single-step reactions between primary cosmic-ray projectiles and interstellar medium targets. We examine both assumptions by using a semiempirical description for the spall's energy distribution and by including the reactions that proceed via intermediary fragments. After relaxing the straight-ahead approximation, we find that the changes in the production rates and emerging fluxes are small and do not warrant rejection of this approximation. In contrast, we discover that two-step reactions can alter the production rate considerably, leading to noticeable increases in the efficiency of producing the LiBeB nuclei. Motivated by this result, we introduce a cascade technique to compute the production rates exactly and find that the results differ only slightly from those of our two-step calculations. We thus conclude that terminating the reaction network at the two-step order is sufficiently accurate for current studies of spallation.
14347496
The BBN manifesto
Abstract In this manifesto I review the current status of standard big bang nucleosynthesis in light of recent observational data and discuss the importance of near-future observations as direct tests of the standard BBN.
43916778
Constraints on 17-keV neutrinos.
Recent experiments indicate that a 17-keV neutrino mixes with {nu}{sub {ital e}} with 1% probability. We discuss the constraints from neutrinoless double {beta} decay, cosmology, and astrophysics that any model possessing a 17-keV neutrino must obey. Several recently proposed models are shown to be incompatible with these constraints.
119396716
Big Bang nucleosynthesis constraints on brane cosmologies
Abstract We examine constraints from Big Bang nucleosynthesis on type II Randall–Sundrum brane cosmologies with both a dark radiation component and a quadratic term that depends on the 5-dimensional Planck mass, M 5 . Using limits on the abundances of deuterium and helium-4, we calculate the allowed region in the M 5 –dark radiation plane and derive the precise BBN bound on M 5 alone with no dark radiation: M 5 >13 TeV.
119404050
Constraining the cosmic abundance of stellar remnants with multi - TeV gamma-rays
If stellar remnants are cosmologically significant, the infrared flux from the remnant progenitors would contribute to the opacity of multi-TeV γ-rays. The multi-TeV γ-ray horizon is established to be at a redshift z > 0.034 by the observation of the blazar Mrk 501. By requiring that the optical depth due to γγ → e+e- be less than 1 for a source at z = 0.034, we limit the cosmological density of stellar remnants, Ωrm ≤ (2-4) × 10-3 h (h70 is the Hubble constant in units of 70 km s-1 Mpc-1), and thus strongly constrain stellar remnants as a cosmologically significant source of dark matter.
46692923
Estimates of spin-exchange parameters for alkali-metal-noble-gas pairs.