Quantum Field Theory beyond the Vacuum

This award funds the research activities of Professor Luca Delacrétaz at the University of Chicago. Quantum Field Theory (QFT) is a cornerstone of fundamental physics, unifying high energy, condensed matter, and statistical physics. It is also the most precise description we have of nature. This project aims to deepen our understanding of QFT beyond the relativistic vacuum traditionally studied in particle physics. The research will explore the behaviors and properties of matter under extreme conditions, such as high density and temperature, which are difficult to describe by existing methods. By investigating these states, the project seeks to uncover new principles of physics that could lead to advancements in various fields, including condensed matter physics and cosmology. Additionally, the research will involve the training of graduate students, and participation in outreach activities in Chicago's south side, thereby supporting education in the sciences. This work aligns with NSF's mission to promote the progress of science and to advance national prosperity and welfare. More technically, the project is structured around two main objectives: constraining finite density phases that can emerge from interacting QFTs, and understanding the high-energy spectrum of QFTs through the lens of thermalization, hydrodynamics, and chaos. For the first objective, the research will employ UV/IR constraints and effective field theory (EFT) techniques to map out the possible phases that conformal field theories (CFTs) can flow to at finite density, aiming to either rule out or confirm the existence of exotic phases such as non-Fermi liquids, pair density waves, etc. For the second objective, the project will develop precision tests of thermalization by extending EFTs to capture hydrodynamic behavior and chaotic dynamics in high-energy states. This comprehensive approach aims to bridge the gap between high-energy theoretical predictions and observable phenomena in many-body quantum systems. 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.