Biomedical subjects
Lawrence M Krauss
Publications and source records attributed to Lawrence M Krauss.
New nucleosynthesis constraint on the variation of G.
Big bang nucleosynthesis can provide, via constraints on the expansion rate at that time, limits on possible variations in Newton's constant, G. The original analyses were performed before an independent measurement of the baryon-to-photon ratio from the cosmic microwave background was available. Combining this with recent measurements of the primordial deuterium abundance in quasar absorption systems now allows one to derive a new tighter constraint on G without recourse to considerations of helium or lithium abundances. We find that, compared to today's value, G0, G(BBN)/G(0)=1.01(+0.20)(-0.16) at the 68% confidence level.
Questions that plague physics. Lawrence M. Krauss speaks about unfinished business.
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Age estimates of globular clusters in the Milky Way: constraints on cosmology.
Recent observations of stellar globular clusters in the Milky Way Galaxy, combined with revised ranges of parameters in stellar evolution codes and new estimates of the earliest epoch of globular cluster formation, result in a 95% confidence level lower limit on the age of the Universe of 11.2 billion years. This age is inconsistent with the expansion age for a flat Universe for the currently allowed range of the Hubble constant, unless the cosmic equation of state is dominated by a component that violates the strong energy condition. This means that the three fundamental observables in cosmology-the age of the Universe, the distance-redshift relation, and the geometry of the Universe-now independently support the case for a dark energy-dominated Universe.