arXiv subjects

J. F. Lara

Publications and source records attributed to J. F. Lara.

4 recordsLinked to original sources

arXiv2006

Inhomogeneous Big Bang Nucleosynthesis Revisited

We reanalyze the allowed parameters for inhomogeneous big bang nucleosynthesis in light of the WMAP constraints on the baryon-to-photon ratio and a recent measurement which has set the neutron lifetime to be 878.5 +/- 0.7 +/- 0.3 seconds. For a set baryon-to-photon ratio the new lifetime reduces the mass fraction of He4 by 0.0015 but does not significantly change the abundances of other isotopes. This enlarges the region of concordance between He4 and deuterium in the parameter space of the baryon-to-photon ratio and the IBBN distance scale. The Li7 abundance can be brought into concordance with observed He4 and deuterium abundances by using depletion factors as high as 9.3. The WMAP constraints, however, severely limit the allowed comoving (T = 100 GK) inhomogeneity distance scale to (1.3 - 2.6)x10^5 cm.

astro-ph↗

arXiv2004

Deuterium and Li7 Concordance in Inhomogeneous Big Bang Nucleosynthesis Models

Recent observational constraints on primodial deuterium and Li7 correspond to different values of the baryon-to-photon ratio when applied to the Standard Big Bang Nucleosynthesis (SBBN) model. In this article these constraints are applied to baryon Inhomogeneous (IBBN) models. A depletion factor of 3.4 applied to the Li7 constraints will bring Li7, deuterium and He4 constraints in concordance for both the SBBN and IBBN models. A depletion factor of 6.1 will bring concordance for the IBBN model alone.

astro-ph↗

arXiv2001

Neutrino Heating in an Inhomogeneous Big Bang Nucleosynthesis Model

The effect of the heating of neutrinos by scattering with electrons and positrons and by e-e+ annihilation on nucleosynthesis is calculated for a spherically symmetric baryon inhomogeneous model of the universe. The model has a high baryon density core and a low density outer region. The heating effect is calculated by solving the Boltzmann Transport Equation for the distribution functions of electron and muon/tau neutrinos. For a range of baryon-to-photon ratio = [ 0, 1.5 ] x 10^-10 and distance scale = [ 10^2, 10^8 ] cm the heating effect increases the mass fraction of He4 by a range of [1, 2] x 10^-4. The change of the value of the mass fraction of He4 appears similiar to the change caused by an upward shift in the value of the baryon-to-photon ratio. But the change to deuterium is a decrease in abundance ratio Y(d)/Y(p) on the order of 10^-3, one order less than the decrease due to a shift in baryon-to-photon ratio.

astro-ph↗

arXiv2001

Neutron Diffusion and Nucleosynthesis in an Inhomogeneous Big Bang Model

This article describes the production of primordial He4 nuclei in an inhomogeneous universe. The baryon distribution is spherically symmetric and consists of a high density inner region and a low density outer region. As the temperature decreases neutrons diffuse to the outer region until they are homogeneously distributed, and protons may be redistributed depending on how fast diffusion occurs. Nucleosynthesis occurs earlier in the inner region and neutrons diffuse back to that region. The rapidity of diffusion determines how much He4 is ultimately produced.

astro-ph↗