RUI: Energy Density Fluctuations, Negative Energy Detection and Gravity

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This award supports research to understand the properties of "negative energy." One focus is on methods of indirectly detecting this unusual form of energy using, in part, techniques developed in the field of quantum optics. The PI and a collaborator will work with an experimentalist to determine if such detection is feasible. A second major focus will be to study the distribution of energy fluctuations in the vacuum. Contrary to our experience in everyday life, the laws of quantum physics tell us that "empty" space is not really empty but consists of ever-present fluctuations of energy. The average value of the energy in empty space is zero, as one would expect, but quantum mechanics says that there must be fluctuations around this mean value. In order to average out to zero, there must be both negative as well as positive fluctuations. What is the likelihood then of getting a negative value in a single measurement? Previous work yields a surprisingly high probability for one spatial dimension. Current efforts are geared toward trying to determine the form of this "probability distribution" in the three-spatial-dimensional world in which we live.The laws of quantum mechanics allow the existence of states of energy that are lower than that of the vacuum. If there are no restrictions on negative energy, then bizarre macroscopic effects might become possible. These would include wormholes and warp drives for faster-than light travel, violations of the second law of thermodynamics (e.g., refrigerators with no power sources), and the destruction of black holes. However, the same laws of quantum mechanics which allow this form of energy to exist severely limit its behavior. Typically, the longer the negative energy lasts, the smaller its magnitude. This work lies at the juncture of the fields of quantum theory, Einstein's general relativity, and thermodynamics. The only direct probe of negative energy is gravity, but the amounts of negative energy obtainable in the laboratory are minute. Therefore, one has to resort to indirect detection, such as measuring the effect of negative energy on atomic decay rates. The issue of the form of the probability distribution for energy fluctuations is key to understanding the structure of the vacuum, and has implications for other fields such as cosmology. Undergraduates are being prepared to engage in this research through Mathematica-based courses developed by the PI.