Introduction to Cosmology Third Edition

Author: Matts Roos

Published in: John Wiley & Sons

ISBN: 0 470 84909 6

File Type: pdf

File Size:  2 MB

Language: English


This preface can start just like the previous one: in the seven years since the second edition was finalized, the field of cosmology has seen many important developments, mainly due to new observations with superior instruments. In the past, cosmology often relied on philosophical or aesthetic arguments; now it is maturing to become an exact science. For example, the Einstein–de Sitter universe, which has zero cosmological constant (Ωλ = 0), used to be favoured for esthetical reasons, but today it is known to be very different from zero (Ωλ = 0.73 ± 0.04). In the first edition I quoted Ω0 = 0.8 ± 0.3 (daring to believe in errors that many others did not), which gave room for all possible spatial geometries: spherical, flat and hyperbolic. Since then the value has converged to Ω0 = 1.02 ± 0.02, and everybody is now willing to concede that the geometry of the Universe is flat, Ω0 = 1.

This result is one of the cornerstones of what we now can call the ‘Standard Model of Cosmology’. Still, deep problems remain, so deep that even Einstein’s general relativity is occasionally put in doubt. A consequence of the successful march towards a ‘standard model’ is that many alternative models can be discarded. An introductory text of limited length like the current one cannot be a historical record of failed models. Thus I no longer discuss, or discuss only briefly, k ≠ 0 geometries, the Einstein–de Sitter universe, hot and warm dark matter, cold dark matter models with Λ = 0, isocurvature fluctuations, topological defects (except monopoles), Bianchi universes, and formulae  which only work in discarded or idealized models, like Mattig’s relation and the Saha equation.

Instead, this edition contains many new or considerably expanded subjects: Section 2.3 on Relativistic Distance Measures, Section 3.3 on Gravitational Lensing, Section 3.5 on Gravitational Waves, Section 4.3 on Dark Energy and Quintessence, Section 5.1 on Photon Polarization, Section 7.4 on The Inflaton as Quintessence, Section 7.5 on Cyclic Models, Section 8.3 on CMB Polarization Anisotropies, Section 8.4 on model testing and parameter estimation using mainly the first-year CMB results of the Wilkinson Microwave Anisotropy Probe, and Section 9.5 on large-scale structure results from the 2 degree Field (2dF) Galaxy Redshift Survey. The synopsis in this edition is also different and hopefully more logical, much has been entirely rewritten, and all parameter values have been updated. I have not wanted to go into pure astrophysics, but the line between cosmology and cosmologically important astrophysics is not easy to draw. Supernova explosion mechanisms and black holes are included as in the earlier editions, but not for instance active galactic nuclei (AGNs) or jets or ultra-high-energy cosmic rays.

Observational techniques are mentioned only briefly—they are beyond the scope of this book. There are many new figures for which I am in debt to colleagues and friends, all acknowledged in the figure legends. I have profited from discussions with Professor Carlos Frenk at the University of Durham and Professor Kari Enqvist at the University of Helsinki. I am also indebted to Professor Juhani Keinonen at the University of Helsinki for having generously provided me with working space and access to all the facilities at the Department of Physical Sciences, despite the fact that I am retired. Many critics, referees and other readers have made useful comments that I have tried to take into account. One careful reader, Urbana Lopes França Jr, sent me a long list of misprints and errors. A critic of the second edition stated that the errors in the first edition had been corrected, but that new errors had emerged in the new text. This will unfortunately always be true in any comparison of edition n + 1 with edition n. In an attempt to make continuous corrections I have assigned a web site for a list of errors and misprints.
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