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Zenith Grant Awardee

Dr. Saswat Sarangi

Columbia University


Gary Shiu, <i>University of Wisconsin, Madison</i><br>Benjamin Shlaer, <i>University of Colorado, Boulder</i>

Project Title

Transport Properties of the Multiverse

Project Summary

One of the greatest surprises to come from recent theoretical physics is the description of an incredible number of possible four-dimensional universes. The resulting picture is that empty space is occasionally bubbling new and different universes in much the same way that bubbles of steam form and expand in a hot kettle: But instead of only two possible phases, the 'multiverse' can cook up perhaps 10500 different phases of universe. The question we will address is whether our type of universe is in any sense typical – or even compatible within this new theoretical framework, known as the Landscape.

Our approach is to understand collective behavior in the Landscape. As an analogy, one may study the gross properties of a bottle of soda that determine when bubble nucleation becomes ubiquitous (e.g. when the cap is opened or sugar is added). A more precise analogy is that of transport in a disordered system. Disorder in semi-conductors and metals have a large impact on the mobility of an electron, and determine what the likelihood is for a current to reach a given destination. In the landscape, a probability current flows between universes. Understanding where this current flows is equivalent to understanding which universes are formed.

Technical Abstract

The existence of the cosmic landscape, and the enormous number of vacua that it contains, confronts us with many questions regarding our universe. We would like to know why and how our universe chose the particular site in the landscape that bestowed it with its particular characters. Our approach focuses on the tunneling and the transport properties of the various regions in the landscape. We pursue a bottom-up as well as a top-down approach. The bottom-up approach studies individual tunneling events in the landscape setting such as DBI Coleman-De Luccia instanton, DBI Hawking-Moss, stochastic description of brane fluctuations and resonance tunneling. The complementary top-down approach, motivated by condensed matter literature, investigates the gross properties of the landscape. Instead of focusing on the individual transitions between vacua, we ask questions about the transport properties of the landscape. Here the landscape, with its enormous number of vacua, potential barriers and decay channels is compared with a disordered condensed matter system. In the process we are forced to answer conceptual problems that arise whenever a quantum mechanical description of the entire universe is sought in the presence of gravity. Our work also involves simulations on some landscape models to bridge a gap between statistics of vacua and tunneling dynamics.

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