The Hubble Constant

by: Neal Jackson

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. In the last 20 years, much progress has been made and estimates now range between 60 and 75 km s^-1 Mpc^-1, with most now between 70 and 75 km s^-1 Mpc^-1, a huge improvement over the factor-of-2 uncertainty which used to prevail. Further improvements which gave a generally agreed margin of error of a few percent rather than the current 10% would be vital input to much other interesting cosmology. There are several programmes which are likely to lead us to this point in the next 10 years.

Measuring our Universe from Galaxy Redshift Surveys

by: Ofer Lahav and Yasushi Suto

Galaxy redshift surveys have achieved significant progress over the last couple of decades. Those surveys tell us in the most straightforward way what our local Universe looks like. While the galaxy distribution traces the bright side of the Universe, detailed quantitative analyses of the data have even revealed the dark side of the Universe dominated by non-baryonic dark matter as well as more mysterious dark energy (or Einstein’s cosmological constant). We describe several methodologies of using galaxy redshift surveys as cosmological probes, and then summarize the recent results from the existing surveys. Finally we present our views on the future of redshift surveys in the era of precision cosmology.

Experimental Searches for Dark Matter

by: Timothy J. Sumner

There is now an enormously rich variety of experimental techniques being brought to bear on experimental searches for dark matter, covering a wide range of suggested forms for it. The existence of “dark matter”, in some form or other, is inferred from a number of relatively simple observations and the problem has been known for over half a century. To explain “dark matter” is one of the foremost challenges today — the answer will be of fundamental importance to cosmologists, astrophysicists, particle physicists, and general relativists. In this article, I will give a brief review of the observational evidence (concentrating on areas of current significant activity), followed by an equally brief summary of candidate solutions for the ‘dark matter’. I will then discuss experimental searches, both direct and indirect. Finally, I will offer prospects for the future.

The Cosmological Constant

by: Sean M. Carroll

This is a review of the physics and cosmology of the cosmological constant. Focusing on recent developments, I present a pedagogical overview of cosmology in the presence of a cosmological constant, observational constraints on its magnitude, and the physics of a small (and potentially nonzero) vacuum energy.

The Cosmic Microwave Background

by: Aled Jones and Anthony N. Lasenby

We present a brief review of current theory and observations of the cosmic microwave background (CMB). New predictions for cosmological defect theories and an overview of the inflationary theory are discussed. Recent results from various observations of the anisotropies of the microwave background are described and a summary of the proposed experiments is presented. A new analysis technique based on Bayesian statistics that can be used to reconstruct the underlying sky fluctuations is summarised. Current CMB data is used to set some preliminary constraints on the values of fundamental cosmological parameters $latex \Omega$ and $latex H_\circ$ using the maximum likelihood technique. In addition, secondary anisotropies due to the Sunyaev-Zel’dovich effect are described.