Fundamental Physics and Cosmology

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This award funds the research of Professor Alexander Vilenkin at Tufts University.Recent developments in cosmology suggest that much of the universe is in a state of explosive accelerated expansion, called inflation. We live in a "bubble" where inflation has ended, and other bubbles with diverse properties are constantly being formed. A major unresolved problem in this theory of eternal inflation is the problem of calculating relative probabilities of different measurements. In the course of eternal inflation, any event having a nonzero probability will happen an infinite number of times, and comparing infinities is an inherently ambiguous task. The challenge is to formulate a compelling probability measure prescription. This will put the theory on a much firmer footing and will (at least in principle) allow its observational tests. Another major topic of this research is the evolution and observational signatures of cosmic strings. Strings can be formed as high-energy linear defects in the early universe and can produce a variety of observational effects at the present time. A detection of cosmic strings would be of great importance, as it would open a unique window into the physics of very high energies and into the early history of the universe.This project is also envisioned to have significant broader impacts. The new worldview that has emerged from the eternal inflation scenario has far-reaching implications beyond physics. Professor Vilenkin will continue presenting these ideas in public lectures, in popular articles, and in popular magazine and TV interviews. The research described above will be done with active collaboration of graduate students and postdocs, thus providing crucial training to the young physicists.