The field of relativistic nuclear collisions explores the physics of quantum chromodynamics (QCD) and deconfinement at the highest temperatures and densities ever created in the laboratory. One of the most remarkable discoveries to emerge from this program has been the realization that the dynamical evolution of deconfined QCD matter - also known as quark-gluon plasma (QGP) - can be well described by the equations of relativistic fluid dynamics. Understanding the origins and properties of this fluid dynamical behavior remains one of the foremost outstanding challenges in the field.
In this respect, one of the oldest and most well-established tools for probing the dynamics of relativistic nuclear collisions is provided by Hanbury Brown - Twiss (HBT) intensity interferometry, a technique which allows one to infer geometric properties of a particle-producing source using quantum statistical correlations in momentum space. In this talk, I will briefly discuss the basic physics behind HBT interferometry and how it can shed light on the hydrodynamical evolution of nuclear collisions. I will also present two studies which have helped to elucidate the connection between geometry and fluid flow in these systems, and which may be used to illustrate some of the ways in which interferometry can be applied in other disciplines.