String Theory and the CMB (audio only)

Liam McAllister, Associate Professor of Physics, Cornell University

I will explain how observations of the very early universe give us a window on quantum gravity. The broad-brush predictions of inflationary cosmology agree beautifully with all measurements, but the microphysical laws underlying inflation are still unknown. I will show why these laws must be rooted in a theory of quantum gravity, such as string theory. I will then describe what we can learn about quantum gravity by detecting, or setting limits on, the imprints of quantum fluctuations of the gravitational field in B-mode polarization of the CMB.