ABSTRACT
The standard, hot big bang cosmology is remarkably successful. It provides a reliable and tested account of the history of the Universe from at least as early as the time of the synthesis of the light elements until today. The standard cosmology is quite an achievement, comparable to that of the standard model of low-energy particle physics, the gauge theory of the strong, weak, and electromagnetic interactions. The cosmological puzzles that the standard cosmology raises involve a handful of very fundamental cosmological facts that the model can accommodate, but whose ultimate origin it has yet to elucidate. The Robertson-Walker metric describes a space that is homogeneous and isotropic. The basic idea of inflation is that there was an epoch when vacuum energy was the dominant component of the energy density of the Universe, so that the scale factor grew exponentially.
