The New Cosmology

PREFACE

CONTENTS

Measuring distances to extragalactic objects has been a focal point for cosmology over the past 100 years, shaping (sometimes incorrectly) our view of the Universe. I discuss the history of measuring distances, briefly review several popular distance measuring techniques used over the past decade, and critique our current knowledge of the current rate of the expansion of the Universe, H₀, from these observations. Measuring distances back to a significant portion of the look back time probes the make-up of the Universe, through the effects of different types of matter on the cosmological geometry and expansion. Over the past five years two teams have used type Ia supernovae to trace the expansion of the Universe to a look back time more than 70% of the age of the Universe. These observations show an accelerating Universe which is best explained by a cosmological constant, or other form of dark energy with an equation of state near w = p/ρ = −1. There are many possible lurking systematic effects. However, while difficult to completely eliminate, none of these appears large enough to challenge current results. However, as future experiments attempt to better characterize the equation of state of the matter leading to the observed acceleration, these systematic effects will ultimately limit progress.

I present a pedagogical review of inflation and the cosmic microwave background. I describe how a short period of accelerated expansion can replace the special initial conditions of the standard big bang model. I also describe the development of CMBology: the study of the cosmic microwave background. This cool (3 K) new cosmological tool is an increasingly precise rival and complement to many other methods in the race to determine the parameters of the Universe: its age, size, composition and detailed evolution.

These three lectures give an introduction to galaxy redshift surveys as probes of the large-scale structure in the Universe, and describe recent measurements of fundamental cosmological parameters from both the redshift surveys and observations of the cosmic microwave background. The first lecture deals with the large-scale structure (LSS) revealed by the galaxy distribution, and its interpretation in terms of cosmological parameters. The topics covered include: a descriptive review of large-scale structure; redshift surveys, cosmography and cosmology; the statistical characterization of LSS; an introduction to the theory of structure formation; the density and velocity fields; bias and the relation of light to mass; redshift-space distortions; the observed correlation function and power spectrum; and the Gaussianity and topology of the density field. The second lecture discusses the current state of the art in redshift surveys, describing the results on large-scale structure and cosmology emerging from the 2dF Galaxy Redshift Survey (2dFGRS). The third lecture discusses the important new results from observations of the cosmic microwave background (CMB) by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite that were reported during the course of the Summer School.

No abstract received.

The epoch of galaxy formation, occurring between one and six billion years after the Big Bang, was initiated by the collapse of over-dense regions of matter, resulting in extraordinary bursts of star formation, rapid growth of massive nuclear black holes, and the rapid structural evolution of the early universe. To understand these phenomena and thus gain insight into the evolution of galaxies in general is a central objective of modern astrophysics. Here, we summarize some important theoretical problems in galaxy formation and review recent data obtained on the ultra-steep spectrum radio sources. These are found in the densest regions of the early universe, and are associated with AGN in the most massive galaxies embedded in what will become the most massive clusters of the present-day universe.

These lectures present a brief overview of what we know about dark matter in galaxies. I will stress some of the current problems.

Neutral atomic hydrogen is an endangered species at the present age of the Universe. When hydrogen is dispersed at low density in the intergalactic medium, the gas is vulnerable to photoionization, and once ionized, the time for recombination exceeds the Hubble time. If hydrogen clouds are confined to sufficient density that they are self-shielding to the ionizing background, they are vulnerable to instability, collapse and star formation, which over time, locks the hydrogen into long lived stars. When neutral clouds do exist after the Epoch of Reionization, they associate closely with galaxies; in these locations, they provide valuable kinematical tracers of the gravitational potentials that bind galaxies and groups.

For decades, gravitational lensing has been recognised as the most powerful method for measuring the mass of an astronomical object, in particular instances of near perfect alignment between background sources and foreground masses. Techniques to extend lensing methods to measure cosmological parameters are more recent. These lectures discuss the methodology of estimating the cosmological parameters, and present some of the best measurements to date.

In the first Lecture, the Big Bang and the Standard Model of particle physics are introduced, as well as the structure of the latter and open issues beyond it. Neutrino physics is discussed in the second Lecture, with emphasis on models for neutrino masses and oscillations. The third Lecture is devoted to supersymmetry, including the prospects for discovering it at accelerators or as cold dark matter. Inflation is reviewed from the viewpoint of particle physics in the fourth Lecture, including simple models with a single scalar inflaton field: the possibility that this might be a sneutrino is proposed. Finally, the fifth Lecture is devoted to topics further beyond the Standard Model, such as grand unification, baryo- and leptogenesis — that might be due to sneutrino inflaton decays — and ultra-high-energy cosmic rays — that might be due to the decays of metastable superheavy dark matter particles.