相关论文: Prospects and Limitations for Constraining Light R…
Detections of deuterium in high redshift Lyman limit absorption systems along the line of sight to QSOs promise to reveal the primordial deuterium abundance. At present, the deuterium abundances (D/H) derived from the very few systems…
Relic density calculations are often used to constrain particle physics models, and in particular supersymmetry. We will show that the presence of additional energy or entropy before the Big-Bang nucleosynthesis can however completely…
We investigate the modifications to predictions for the abundances of light elements from standard Big-Bang nucleosynthesis when exotic late-decaying particles with lifetimes exceeding ~1 sec are prominent in the early Universe. Utilising a…
We carried out an exploratory analysis of the contribution of the underlying stellar absorption to the total uncertainty of the abundance of primordial helium using simple stellar populations models and observational data from the Sloan…
Primordial nucleosynthesis is inevitable during the early evolution of an expanding universe filled with radiation and matter (baryons). However, the precise abundance yields depend sensitively on the baryon density, the radiation content…
The discrepancy between the theoretical prediction of primordial lithium abundances and astronomical observations is called the Lithium Problem. We find that extra contributions from non-thermal hydrogen and helium during Big Bang…
The remarkable agreement between observations of the primordial light element abundances and the corresponding theoretical predictions within the standard cosmological history provides a powerful method to constrain physics beyond the…
Within the standard models of particle physics and cosmology we have calculated the big-bang prediction for the primordial abundance of \he to a theoretical uncertainty of less than $0.1 \pct$ $(\delta Y_P < \pm 0.0002)$, improving the…
Currently, the primordial helium abundance is best estimated through spectroscopic observations of H II regions in metal-poor galaxies. However these determinations are limited by several systematic uncertainties which ultimately limit our…
Tests of big bang nucleosynthesis and early universe cosmology require precision measurements for helium abundance determinations. However, efforts to determine the primordial helium abundance via observations of metal poor H II regions…
Recent measurements of the D(p,$\gamma)^3$He, nuclear reaction cross-section and of the neutron lifetime, along with the reevaluation of the cosmological baryon abundance from cosmic microwave background (CMB) analysis, call for an update…
We show that a nonstandard cosmological history with a period of early matter domination driven by a sub-TeV visible-sector particle can arise rather naturally. This scenario involves a long-lived standard model singlet that acquires a…
Abundance measurements of the light elements lithium, beryllium, and boron are playing an increasingly important role in the study of stellar physics. Because these elements are easily destroyed in stars at temperatures 2--4 million K, the…
In some models of thermal relic dark matter, the relic abundance may be set by inelastic scattering processes (rather than annihilations) becoming inefficient as the universe cools down. This effect has been called coscattering. We present…
We investigate the relic abundance of asymmetric Dark Matter particles that were in thermal equilibrium in the early universe. The standard analytic calculation of the symmetric Dark Matter is generalized to the asymmetric case. We…
We present an improved calculation of the light element abundances in the framework of Big Bang nucleosynthesis as a function of the Higgs vacuum expectation value $v$. We compare the methods of our calculation to previous literature…
We place bounds on long-lived primordial relics using measurements of the diffuse gamma ray spectrum from EGRET and COMPTEL. Bounds are derived for both radiative and hadronic decays with stronger bounds applying for the latter decay mode.…
We use here a family of scaling transformations, that scale key rates in the evolution equations, to analytically understand constraints on light relics from cosmic microwave background (CMB) maps, given cosmological models of varying…
Models that lead to a cosmological stiff fluid component, with a density $\rho_S$ that scales as $a^{-6}$, where $a$ is the scale factor, have been proposed recently in a variety of contexts. We calculate numerically the effect of such a…
We forecast the expected cosmological constraints from a combination of probes of both the universal expansion rate and matter perturbation growth, in the form of weak lensing tomography, galaxy tomography, supernovae, and the cosmic…