Observing the sky in the microwave region of the spectrum allows us to directly image the universe when it was just a few hundred thousand years old. The universe was much simpler then, simple enough that its expected statistical properties, given a model, can be calculated with high accuracy. Recent improvements in measurement resolution and sensitivity, most notably from the Planck satellite, but also from the South Pole Telescope, have provided precision tests of the standard cosmological model. In this colloquium I will introduce the cosmic microwave background (CMB) and the standard cosmological model. I will explain the nature of these precision tests and what we are learning about the origin of all structure in the universe, and about the background of neutrinos thermally produced in the big bang. I will also cover how the improvements in resolution and sensitivity are opening up a new window on the dark universe, via gravitational lensing of the CMB. 

Close to the absolute zero of temperature, when pushed to the edge between two phases of matter, simple lattice Hamiltonians of spins can display the incredibly rich phenomena of "quantum criticality". Quantum critical ground states are described by the most complex wavefunctions known to physicists, yet they can be categorized by "universality classes" that are independent of the details of the Hamiltonians that realize them. In this colloquium I will show how such quantum critical spin systems can arise in real-world materials, and explain our successes in developing quantum many-body simulations of a new universality class of deconfined quantum critical points. 

Tracing the Formation of Massive Galaxies in the Early Universe

The average rate at which galaxies are forming stars in the Universe has decreased by more than an order of magnitude over the last 10 billion years. Understanding why certain galaxies shut off their star formation activity, while others do not is one of the key unanswered questions in astrophysics today. Observations in the local Universe suggest that the mechanism responsible for quenching star formation in galaxies may be intimately linked to their structural transformation. In order to test quenching scenarios, however, it is vital to look beyond the local Universe and identify the first generation of quiescent galaxies at high redshift. I will discuss my work studying the first massive systems to appear on the quiescent "red sequence" at redshifts z>1, when the universe was less than half its current age. I will show that the properties of these galaxies are challenging not only our understanding of how star formation is quenched in galaxies, but also how mass is assembled in a hierarchical universe. I will also highlight how future work with the CANDELS survey, as well as the next generation of astronomical facilities coming online over the next 5-10 years, will help establish the primary mechanisms responsible for star-formation quenching and will revolutionize our understanding of how the most massive galaxies in the Universe formed.