The greatest challenge in modern cosmology is to develop a consistent theory of the origin and evolution of density perturbations in the universe. Observationally, on all but the largest scales the visible matter in the universe is inhomogeneous and anisotropic, while the Cosmic Microwave Background radiation is extraordinarily isotropic. The answer to this problem is believed to reside in the very early universe, and hence falls into the realm of particle cosmology, where quantum field theory and cosmology intersect.

The most likely source of primordial perturbations is in the rich physics of the symmetry-breaking phase transitions required to fracture the single super-unified force believed to be present in the earliest moments of the universe into the four distinct forces we observe today.

In this talk I will discuss the observations and theoretical prejudices underlying this picture, and describe a particularly rich class of models - the so-called topological defects - which almost inevitably emerge from it.

Snacks will be provided.

See Conundrum Talks for more information about this series.