HEP/Astro Journal Club -- 16 March 2001

Square pegs, round holes: Solving BBN + CMB

Jim Kneller (OSU)

Abstract

For many years the best determinations of the baryon to photon ratio (η) of the universe were made by the comparison of the predictions of big bang nucleosynthesis (BBN) with the observed abundances of the lightest nuclei. Measurment of the anisotropies in the cosmic microwave background (CMB) provide an independent method for determining this same ratio and in the last year two experiments, BOOMERANG and MAXIMA, have made sufficiently accurate measurements of the anisotopy to determine the ratio as precisely as BBN. The two determinations are significantly different. In this talk I shall discuss how the situation can be resolved by using electron neutino degeneracy and additional relativistic energy to modify the range of η allowed by BBN and show that there is a solution at the cost of a significant degeneracy for electron neutrinos (∼ 0.1) and possibly μ and/or τ neutrinos too.

References

G. Steigman, J. P. Kneller and A. Zetner, “CMB (and other) challenges to BBN,” astro-ph/0102152.

J. P. Kneller, R. J. Scherrer, G. Steigman and T. P. Walker, “When does CMB + BBN = new physics?” astro-ph/0101386.

12:30, Smith Lab 4079