Gravity and Spacetime Fluctuations
We know that Einstein's General Relativity is incomplete, as gravity must somehow be quantum mechanical. I study spacetime fluctuations due to the quantum nature of spacetime.
It has generally been thought that, because of the low energies of experiments relative to the Planck scale, that it will be impossible to see experimental signatures of quantum gravity in the laboratory. We have been considering whether this common lore is true in the context of soft effects in quantum gravity where holography naturally plays a role. The quantum gravity of subregions has shown itself to be important in our understanding of these effects, and we have come to understand that near a causal horizon, gravity has properties of a fluid that allows spacetime fluctuations to have infrared effects. Our results suggest that not only the Planck scale but also the light crossing time of an apparatus enters into the size of quantum effects.
If the scale of the experiment enters into a quantum gravity effect, we have the chance to observe it. We have been exploring these ideas theoretically in the QuRIOS Collaboration (Quantum gRavity and Its Observational Signatures), and are beginning to explore them with the GQuEST experiment.
While we have developed these ideas, in the context of the QuRIOS collaboration, through a formally theoretical line of inquiry, their physical intuition is rooted in cosmology, highlighting the importance of working across fields. Inflation is the classic example where quantum effects in the early Universe have imprinted themselves on large-scale structure, in the form of metric fluctuations. For example, I studied how an instability in the potential of the Standard Model Higgs boson could impact the successful predictions of inflation, by creating a negative energy vacuum patch that grows to devour spacetime. The observables that we consider from the vacuum state of quantum gravity are closely related to those that appear as decoherence and phase effects in an atom interferometer, and we have learned much about gauge-invariant observables in interferometers by studying dark matter imprints. Thus even the most formal aspects of our work are closely connected to and motivated by observation.
New Ideas in Dark Matter Detection >>