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