Lectures given at the NATO Advanced Study Institute on Techniques and Concepts of High Energy Physics, St. Croix, USVI (2002).
astro-ph/0301448.

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Abstract. These four lectures cover four topics in modern cosmology: the cosmological constant, the cosmic microwave background, inflation, and cosmology as a probe of physics at the Planck scale. The underlying theme is that cosmology gives us a unique window on the "physics of nothing," or the quantum-mechanical properties of the vacuum. The theory of inflation postulates that vacuum energy, or something very much like it, was the dominant force shaping the evolution of the very early universe. Recent astrophysical observations indicate that vacuum energy, or something very much like it, is also the dominant component of the universe today. Therefore cosmology gives us a way to study an important piece of particle physics inaccessible to accelerators. The lectures are oriented toward graduate students with only a passing familiarity with general relativity and knowledge of basic quantum field theory.

Table of Contents

INTRODUCTION

RESURRECTING EINSTEIN'S GREATEST BLUNDER

Cosmology for beginners

Einstein's "greatest blunder"

Critical density and the return of the age problem

The vacuum in quantum field theory

Vacuum energy in cosmology

THE COSMIC MICROWAVE BACKGROUND

Recombination and the formation of the CMB

Sachs-Wolfe Effect

Acoustic oscillations and the horizon at last scattering

INFLATION

The flatness problem

The horizon problem

Inflation

Inflation from scalar fields

Density fluctuations from inflation

The primordial power spectrum

A worked example

Inflationary "zoology" and the CMB

LOOKING FOR SIGNS OF QUANTUM GRAVITY IN INFLATION

CONCLUSION

REFERENCES