Quantum fields in and out of equilibrium via spinor Bose-Einstein condensates

forthcoming

Our understanding of the physical world, from cosmological distances to subatomic scales, is based on field theories, with General Relativity and the Standard Model among the most validated descriptions of reality. Despite their history of success, the application of field theories, particularly in the quantum domain, is still characterized by a rich set of open questions related to processes in- and out-of-equilibrium. A paradigmatic example of a process in which field theories are successfully applied is that of first-order phase transitions. In this case, the dynamics of a system far from equilibrium cannot simply be described in terms of a perturbation of a steady state, but instead require combined tools and concepts taken from statistical and quantum mechanics. The transition results from the dynamics between field values associated with local minima of the system's energy. In the quantum regime, these local minima correspond to the so-called vacuum state of the field, making the problem well-defined but, surprisingly, exactly solvable in only a few simple cases. Relaxation dynamics between different vacua, commonly known as False Vacuum Decay (FVD), is a case study that has significant impacts in broad and interdisciplinary research areas. Models have been proposed to estimate the decay rate, entanglement generation at the beginning of the decay, the dynamics of decay products, and the generation of topological defects at the end of the relaxation process. However, our knowledge to date is limited by a substantial lack of experimental observations. This project aims to experimentally realize FVD and other challenging quantum field theories, both in the perturbative and in the non-perturbative regimes, such as confinement physics, using ultracold atomic spin mixtures through proper mapping of the atomic wave function into a quantum field representation and a unique set-up that ensures extremely stable magnetic field conditions.