Research on Quantum Fluctuation Effects and Gravity

Tufts University, Medford MA

Investigators

Abstract

This award supports studies of large quantum energy density fluctuations and their physical effects. These fluctuations are more likely than was previously expected, and their study could lead to new insights into both quantum physics and gravitation. Large energy density fluctuations can lead to large fluctuations of spacetime geometry, which is an aspect of quantum gravity. This work can help clarify the relation between relativity theory and quantum theory, which is major unsolved problem in fundamental physics. It may also help understand the processes in the early history of our universe, such as phase transitions and black hole nucleation. The project will also study analog models in condensed matter systems, such as light propagation in nonlinear optical materials and density fluctuations in liquids. The results may have application to other areas of science and possibly to technology. The project will contribute to education through the participation of students, and development of new ways to explain subtle concepts to students. This research will study probability distributions for spacetime averaged quantum stress tensors, and their physical applications. These distributions have been shown to fall relatively slowly, leading to a relatively large probability of large fluctuations. The details of this effect will be studied in more detail through a combination of analytic and numerical methods. The physical implications of the large fluctuations will also be studied. These may include increased rates of false vacuum decay, which will have implications for the study of phase transitions in the early universe, and nucleation of primordial black holes. Analog models, such as quantum density fluctuations in fluids, will also be studied. Here the probability distribution is expected to be similar to those for quantum stress tensor fluctuations, and may be accessible to experimental investigation. The role of large quantum stress tensor fluctuations in producing passive fluctuations of gravity and their effects will also be studied. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.