Signatures of Excited Initial States and Tunneling in Landscape.

University Of Texas At Austin, Austin TX

Investigators

Abstract

This award funds the research activities of Professor Sonia Paban at the University of Texas at Austin. A wealth of experimental data over the past two decades has led to a successful model of the evolution of the universe known as the Ë-CDM model. This model includes a sudden moment when space-time started expanding, followed by a period of exponential expansion known as cosmic inflation. At the end of cosmic inflation the universe looked pretty much the same in all directions and did not have a center; there were only slight variations due to the quantum nature of the fields. These predictions of cosmic inflation match extremely well the recent data collected on the Cosmic Microwave Background, and they are fairly robust in that they are mostly, but not completely, independent of the detailed structure of space-time before inflation began. Professor Paban will investigate whether the precision of future planned experiments is sufficient to shed light on that detailed structure. Another aspect of this project relates to quantum tunneling: a quantum particle can sometimes cross a barrier via a transition which is forbidden for a classical particle. One proposed explanation of dark energy involves the multiverse --- a landscape of universes. Transitions in the multiverse happen via quantum tunneling. Models of the multiverse contain a large number of fields, whereas most of what we know about quantum tunneling has been limited to a single field. As a result, research in this area advances the national interest by promoting the progress of science in one of its most fundamental directions: the discovery and understanding of the universe. Professor Paban will investigate the dependence of the tunneling rate on the number of fields. The broader impacts of this grant includes the mentoring of graduate students, who will collaborate in this research, as well as Professor Paban's continued mentoring of underrepresented minority undergraduate students. More technically, inflation has the power to erase initial anisotropies on the metric in few e-foldings. For this reason, it has been assumed that it will be impossible to tell if the pre-inflationary metric was anisotropic. Previous work by Paban and collaborators indicates that with the increased precision of projected observations (e.g., the 21cm experiments) it will be possible to exclude or detect such a scenario when the number of e-foldings is around 60. The work proposed here will tell if there is also a distinctive signature for Large Scale Structure measurements, ì-distortion measurements, and observations of oscillations in the power spectrum through a polarization measurement. This research will also determine if there is a distinctive signature in these three future experiments for inflationary periods that are preceded by tunneling and a period of fast-roll. Recent work claims that tunneling in a multi-dimensional space of fields is enhanced as the number of fields grows. This proposal seeks to reproduce or invalidate these results by means of independent computations, including use of exact results and numerical Monte Carlo techniques.