Invited Review given at the Nobel Symposium, "Particle Physics and the Universe", Haga Slott, Sweden, August, 1998. Published in Physica Scripta, Vol. T85, 37-46, 2000

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DETERMINATION OF COSMOLOGICAL PARAMETERS

Wendy L. Freedman

Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101


ABSTRACT. Rapid progress has been made recently toward the measurement of cosmological parameters. Still, there are areas remaining where future progress will be relatively slow and difficult, and where further attention is needed. In this review, the status of measurements of the matter density (Omegam), the vacuum energy density or cosmological constant (OmegaLambda), the Hubble constant (H0), and ages of the oldest measured objects (t0) are summarized. Many recent, independent dynamical measurements are yielding a low value for the matter density (Omegam ~ 0.3). New evidence from type Ia supernovae suggests that OmegaLambda may be non-zero. Many recent Hubble constant measurements appear to be converging in the range of 65-75 km/sec/Mpc. Eliminating systematic errors lies at the heart of accurate measurements for all of these parameters; as a result, a wide range of cosmological parameter space is currently still open. Fortunately, the prospects for accurately measuring cosmological parameters continue to increase and there is good reason for optimism that success may shortly be forthcoming.


Table of Contents

INTRODUCTION AND BRIEF HISTORICAL OVERVIEW

DETERMINATION OF Omegam

DETERMINATION OF OmegaLambda

DETERMINATION OF H0
Gravitational Lenses
Sunyaev Zel'dovich Effect and X-Ray Measurements
The Extragalactic Distance Scale

DETERMINATION OF t0

THE COSMIC MICROWAVE BACKGROUND RADIATION AND COSMOLOGICAL PARAMETERS

DISCUSSION AND SUMMARY

REFERENCES

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