Particle Physics in the Early Universe

Abstract

Perhaps the most striking illustration of the true unity of science is the development of the interdisciplinary field of “particle cosmology.” Particle physics examines nature on the smallest scales, while cosmology studies the universe on the largest scales. Although the two fields are separated by the scales of the objects they study, they are unified because it is impossible to understand the origin and evolution of large-scale structures in the universe without understanding the “initial conditions” that led to the structures. The initial data was set in the very early universe when the fundamental particles and forces acted to produce the perturbations in the cosmic density field. A complete understanding of the present structure of the universe will also be impossible without accounting for the dark component in the density field. The most likely possibility is that this ubiquitous dark component is an elementary particle relic from the early universe.