Enhanced Heavy-Element Formation in Baryon-Inhomogeneous Big-Bang Models

We show that primordial nucleosynthesis in baryon inhomogeneous big-bang models can lead to significant heavy-element production while still satisfying all the light-element abundance constraints including the low lithium abundance observed in population II stars. The parameters which admit this solution arise naturally from the process of neutrino induced inflation of baryon inhomogeneities prior to the epoch of nucleosynthesis. These solutions entail a small fraction of baryons (\le 2\%) in very high density regions with local baryon-to-photon ratio $\eta^h\approx 10^{-4}$, while most baryons are at a baryon-to-photon ratio which optimizes the agreement with light-element abundances. The model would imply a unique signature of baryon inhomogeneities in the early universe, evidenced by the existence of primordial material containing heavy-element products of proton and alpha- burning reactions with an abundance of $[Z]\sim -6 to -4$.Comment: 19 pages in plain Tex, 5 figures (not included) available by fax or mail upon request, ApJ in press, L

Constraints on the Evolution of the Primordial Magnetic Field from the Small-Scale Cosmic Microwave Background Angular Anisotropy

Recent observations of the cosmic microwave background (CMB) have extended the measured power spectrum to higher multipoles $l\gtrsim$1000, and there appears to be possible evidence for excess power on small angular scales. The primordial magnetic field (PMF) can strongly affect the CMB power spectrum and the formation of large scale structure. In this paper, we calculate the CMB temperature anisotropies generated by including a power-law magnetic field at the photon last-scattering surface (PLSS). We then deduce an upper limit on the PMF based on our theoretical analysis of the power excess on small angular scales. We have taken into account several important effects such as the modified matter sound speed in the presence of a magnetic field. An upper limit to the field strength of $|B_\lambda|\lesssim$ 4.7 nG at the present scale of 1 Mpc is deduced. This is obtained by comparing the calculated theoretical result including the Sunyaev-Zeldovich (SZ) effect with recent observed data on the small-scale CMB anisotropies from the $Wilkinson Microwave Anisotropy Probe$ (WMAP), the Cosmic Background Imager (CBI), and the Arcminute Cosmology Bolometer Array Receiver (ACBAR). We discuss several possible mechanisms for the generation and evolution of the PMF.Comment: 27 pages, 4 figures, accepted to ApJ April 10, 200

Delayed childbearing: more women are having their first child later in life

Of particular interest to both researchers and the public is the "average" age of women when they have a child, especially their first. Age at first birth influences the total number of births that a woman might have in her life, which impacts the size, composition, and future growth of the population. The age of the mother, both younger and older, plays a strong role in a wide range of birth outcomes (e.g., birthweight, multiple births, and birth defects), so it is critical to track the average age at which women have their first birth.T.J. Mathews and Brady E. Hamilton.Caption title."August 2009."Also available via the World Wide Web.Includes bibliographical references (p. 7-[8])