Research on Quantum Fluctuation Phenomena and Gravity

Tufts University, Medford MA

Investigators

Abstract

This grant supports investigation on large quantum fluctuations of energy density and pressure and their physical effects. Recent work by the PI and his collaborators has shown that these fluctuations are much less rare than previously thought. Large pressure fluctuations may be able to push quantum particles, such as electrons, over potential barriers at a rate which might be observable and have technological consequences. Large energy density fluctuations can cause the nucleation of bubbles of a new phase in the early universe, which could play a role in the evolution of the universe. These fluctuations can also alter the gravitational field and influence the propagation of light rays. This is an effect of quantum gravity, and its study will help to elucidate the relation between quantum theory and relativity theory, which is one of the unsolved problems of theoretical physics. The project will also study analog models for quantum gravity involving nonlinear optics, and the results may lead to a deeper understanding of optics, as well as quantum gravity. Both undergraduate and graduate students will participate in the research. Some of the results of the project should help to illustrate subtle concepts of quantum theory and relativity to students. This research will focus on the probability distributions for spacetime averages of quantum stress tensor operators. Past work on this topic has focused only on time averages. Here the effects of spatial averaging will also be included. The applications of the probability distributions to several systems will also be investigated. These include the effects of stress tensor fluctuations in enhancing the rates for quantum barrier penetration and in increasing the rates of false vacuum decay, both of which could have significant applications. The role of stress tensor fluctuations in driving spacetime geometry fluctuations will also be studied. One effect of geometry fluctuations will be light cone fluctuations. One approach to be used is an analog model in which squared electric field vacuum fluctuations in a nonlinear dielectric cause light speed fluctuations. This effect can give useful insights into quantum gravity effects, and is of interest in its own right and might be experimentally observable. The role of stress tensor fluctuation in cosmological models will also be studied.