10 research outputs found
The Hubble Constant
I review the current state of determinations of the Hubble constant, which
gives the length scale of the Universe by relating the expansion velocity of
objects to their distance. There are two broad categories of measurements. The
first uses individual astrophysical objects which have some property that
allows their intrinsic luminosity or size to be determined, or allows the
determination of their distance by geometric means. The second category
comprises the use of all-sky cosmic microwave background, or correlations
between large samples of galaxies, to determine information about the geometry
of the Universe and hence the Hubble constant, typically in a combination with
other cosmological parameters. Many, but not all, object-based measurements
give values of around 72-74km/s/Mpc , with typical errors of 2-3km/s/Mpc.
This is in mild discrepancy with CMB-based measurements, in particular those
from the Planck satellite, which give values of 67-68km/s/Mpc and typical
errors of 1-2km/s/Mpc. The size of the remaining systematics indicate that
accuracy rather than precision is the remaining problem in a good determination
of the Hubble constant. Whether a discrepancy exists, and whether new physics
is needed to resolve it, depends on details of the systematics of the
object-based methods, and also on the assumptions about other cosmological
parameters and which datasets are combined in the case of the all-sky methods.Comment: Extensively revised and updated since the 2007 version: accepted by
Living Reviews in Relativity as a major (2014) update of LRR 10, 4, 200
Does Economics have an Effect? Towards an Economics of Economics
"Due to its formality and highly analytic thinking, economics is often attributed a leading role among the social sciences and a prominent position as contributor to economic or social issues in the real world. Fact is, however, that the empirical proof for such a claim is either missing or anecdotal. This paper aims to outline the “economics of economics”. It surveys and compares approaches of impact measurement such as a production function of economics or the demand and supply of trained economists and discusses the determinants of the strength of the influence of economics. It furthermore discriminates between the impact of economic ideas versus that of economists as scientists or politicians.
How Influential is Economics?
economic policy, economics, economists, influence, politics, A11, A12, A13, B40, F20, J20,