Princeton University/Institute for Advanced Study Early Universe/Cosmology Lunch Discussion

Organizers are David Spergel, Princeton University, and Matias Zaldarriaga, Institute for Advanced Study. The lunch will be held at either Princeton University or the Institute for Advanced Study. Check the calendar for the meeting location. This week's meeting is at Princeton University. Attendees can bring their lunch. ABSTRACT: Inflationary cosmology was proposed by Alan Guth in 1980 to explain the large-scale smoothness, isotropy, and flatness of the Universe, as well as to dilute an excess of magnetic monopoles. At very early times, a small causally connected region grows exponentially to encompass the portion that will become our observable Universe today, thereby smoothing out any inhomogeneities. An important byproduct of this rapid expansion phase is the density perturbations that are the seeds of galaxies and other large structures today. Both the density perturbations and gravity waves produced by inflation provide sensitive tests of individual inflationary models. In 1990 my collaborators and I proposed natural inflation, in which shift symmetries explain the required properties of the potential. In the past decade predictions of inflation have been tested and found to come true: the Universe is flat; the density fluctuations are nearly scale invariant. Recently the Planck satellite has made key observations about inflation. The basic idea of inflation matches the data and sensitive tests have been made of individual models. Remarkably, single-field models provide the best match to data, including the lack of nonGaussianities. While many models are ruled out, the original natural inflation as well as modern variants remains viable. The successes of inflation will be reviewed in this talk and the important contributions made by the Planck satellite emphasized.