BBN and the Primordial Abundances

The relic abundances of the light elements synthesized during the first few minutes of the evolution of the Universe provide unique probes of cosmology and the building blocks for stellar and galactic chemical evolution, while also enabling constraints on the baryon (nucleon) density and on models of particle physics beyond the standard model. Recent WMAP analyses of the CBR temperature fluctuation spectrum, combined with other, relevant, observational data, has yielded very tight constraints on the baryon density, permitting a detailed, quantitative confrontation of the predictions of Big Bang Nucleosynthesis with the post-BBN abundances inferred from observational data. The current status of this comparison is presented, with an emphasis on the challenges to astronomy, astrophysics, particle physics, and cosmology it identifies.Comment: To appear in the Proceedings of the ESO/Arcetri Workshop on "Chemical Abundances and Mixing in Stars in the Milky Way and its Satellites", eds., L. Pasquini and S. Randich (Springer-Verlag Series, "ESO Astrophysics Symposia"

The Uncertainty in Newton's Constant and Precision Predictions of the Primordial Helium Abundance

The current uncertainty in Newton's constant, G_N, is of the order of 0.15%. For values of the baryon to photon ratio consistent with both cosmic microwave background observations and the primordial deuterium abundance, this uncertainty in G_N corresponds to an uncertainty in the primordial 4He mass fraction, Y_P, of +-1.3 x 10^{-4}. This uncertainty in Y_P is comparable to the effect from the current uncertainty in the neutron lifetime, which is often treated as the dominant uncertainty in calculations of Y_P. Recent measurements of G_N seem to be converging within a smaller range; a reduction in the estimated error on G_N by a factor of 10 would essentially eliminate it as a source of uncertainty in the calculation of the primordial 4He abundance.Comment: 3 pages, no figures, fixed typos, to appear in Phys. Rev.

The neutrino signal at HALO: learning about the primary supernova neutrino fluxes and neutrino properties

Core-collapse supernova neutrinos undergo a variety of phenomena when they travel from the high neutrino density region and large matter densities to the Earth. We perform analytical calculations of the supernova neutrino fluxes including collective effects due to the neutrino-neutrino interactions, the Mikheev-Smirnov-Wolfenstein (MSW) effect due to the neutrino interactions with the background matter and decoherence of the wave packets as they propagate in space. We predict the numbers of one- and two-neutron charged and neutral-current electron-neutrino scattering on lead events. We show that, due to the energy thresholds, the ratios of one- to two-neutron events are sensitive to the pinching parameters of neutrino fluxes at the neutrinosphere, almost independently of the presently unknown neutrino properties. Besides, such events have an interesting sensitivity to the spectral split features that depend upon the presence/absence of energy equipartition among neutrino flavors. Our calculations show that a lead-based observatory like the Helium And Lead Observatory (HALO) has the potential to pin down important characteristics of the neutrino fluxes at the neutrinosphere, and provide us with information on the neutrino transport in the supernova core.Comment: 30 pages, 12 figures, 6 tables, minor correction

Big Bang Nucleosynthesis with Gaussian Inhomogeneous Neutrino Degeneracy

We consider the effect of inhomogeneous neutrino degeneracy on Big Bang nucleosynthesis for the case where the distribution of neutrino chemical potentials is given by a Gaussian. The chemical potential fluctuations are taken to be isocurvature, so that only inhomogeneities in the electron chemical potential are relevant. Then the final element abundances are a function only of the baryon-photon ratio $\eta$, the effective number of additional neutrinos $\Delta N_\nu$, the mean electron neutrino degeneracy parameter $\bar \xi$, and the rms fluctuation of the degeneracy parameter, $\sigma_\xi$. We find that for fixed $\eta$, $\Delta N_\nu$, and $\bar \xi$, the abundances of helium-4, deuterium, and lithium-7 are, in general, increasing functions of $\sigma_\xi$. Hence, the effect of adding a Gaussian distribution for the electron neutrino degeneracy parameter is to decrease the allowed range for $\eta$. We show that this result can be generalized to a wide variety of distributions for $\xi$.Comment: 9 pages, 3 figures, added discussion of neutrino oscillations, altered presentation of figure

Optimal military spending in the US: A time series analysis

This paper extends previous work on the optimal size of government spending by including nested functional decompositions of military spending into consumption and investment. Post World War II US data are then used to estimate nested non-linear growth models using semi-parametric methods. As expected, investments in military and non-military expenditure are both found to be productive expenditures with respect to the private production. Moreover there is little evidence to suggest that current military spending is having a negative impact on economic growth in the US, while civilian consumption only tends to have only a weak impact. This does not imply that society will necessarily benefit from a reallocation of more spending to the military sector, nor that it is the best way to achieve economic growth. © 2010 Elsevier B.V

Precision Primordial 4^4He Measurement with CMB Experiments

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.Comment: 7 pages, 3 color figures made minor changes to bring inline with journal versio

Chaotic scalar fields as models for dark energy

We consider stochastically quantized self-interacting scalar fields as suitable models to generate dark energy in the universe. Second quantization effects lead to new and unexpected phenomena is the self interaction strength is strong. The stochastically quantized dynamics can degenerate to a chaotic dynamics conjugated to a Bernoulli shift in fictitious time, and the right amount of vacuum energy density can be generated without fine tuning. It is numerically observed that the scalar field dynamics distinguishes fundamental parameters such as the electroweak and strong coupling constants as corresponding to local minima in the dark energy landscape. Chaotic fields can offer possible solutions to the cosmological coincidence problem, as well as to the problem of uniqueness of vacua.Comment: 30 pages, 3 figures. Replaced by final version accepted by Phys. Rev.

Current constraints on Cosmological Parameters from Microwave Background Anisotropies

We compare the latest observations of Cosmic Microwave Background (CMB) Anisotropies with the theoretical predictions of the standard scenario of structure formation. Assuming a primordial power spectrum of adiabatic perturbations we found that the total energy density is constrained to be $\Omega_{tot}=1.03\pm0.06$ while the energy density in baryon and Cold Dark Matter (CDM) are $\Omega_bh^2=0.021\pm0.003$ and $\Omega_{cdm}h^2=0.12\pm0.02$, (all at 68% C.L.) respectively. The primordial spectrum is consistent with scale invariance, ($n_s=0.97\pm0.04$) and the age of the universe is $t_0=14.6\pm0.9$ Gyrs. Adding informations from Large Scale Structure and Supernovae, we found a strong evidence for a cosmological constant $\Omega_{\Lambda}=0.70_{-0.05}^{+0.07}$ and a value of the Hubble parameter $h=0.69\pm0.07$. Restricting this combined analysis to flat universes, we put constraints on possible 'extensions' of the standard scenario. A gravity waves contribution to the quadrupole anisotropy is limited to be $r \le 0.42$ (95% c.l.). A constant equation of state for the dark energy component is bound to be $w_Q \le -0.74$ (95% c.l.). We constrain the effective relativistic degrees of freedom $N_\nu \leq 6.2$ and the neutrino chemical potential $-0.01 \leq \xi_e \leq 0.18$ and $|\xi_{\mu,\tau}|\leq 2.3$ (massless neutrinos).Comment: The status of cosmological parameters before WMAP. In press on Phys. Rev. D., Rapid Communication, 6 pages, 5 figure

Residence Time Statistics for Normal and Fractional Diffusion in a Force Field

We investigate statistics of occupation times for an over-damped Brownian particle in an external force field. A backward Fokker-Planck equation introduced by Majumdar and Comtet describing the distribution of occupation times is solved. The solution gives a general relation between occupation time statistics and probability currents which are found from solutions of the corresponding problem of first passage time. This general relationship between occupation times and first passage times, is valid for normal Markovian diffusion and for non-Markovian sub-diffusion, the latter modeled using the fractional Fokker-Planck equation. For binding potential fields we find in the long time limit ergodic behavior for normal diffusion, while for the fractional framework weak ergodicity breaking is found, in agreement with previous results of Bel and Barkai on the continuous time random walk on a lattice. For non-binding potential rich physical behaviors are obtained, and classification of occupation time statistics is made possible according to whether or not the underlying random walk is recurrent and the averaged first return time to the origin is finite. Our work establishes a link between fractional calculus and ergodicity breaking.Comment: 12 page

Stringent Constraints on Cosmological Neutrino-Antineutrino Asymmetries from Synchronized Flavor Transformation

We assess a mechanism which can transform neutrino-antineutrino asymmetries between flavors in the early universe, and confirm that such transformation is unavoidable in the near bi-maximal framework emerging for the neutrino mixing matrix. We show that the process is a standard Mikheyev-Smirnov-Wolfenstein flavor transformation dictated by a synchronization of momentum states. We also show that flavor ``equilibration'' is a special feature of maximal mixing, and carefully examine new constraints placed on neutrino asymmetries. In particular, the big bang nucleosynthesis limit on electron neutrino degeneracy xi_e < 0.04 does not apply directly to all flavors, yet confirmation of the large-mixing-angle solution to the solar neutrino problem will eliminate the possibility of degenerate big bang nucleosynthesis.Comment: 11 pages, 6 figures; minor changes to match PRD versio