Cosmology, inflation, and the physics of nothing
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.