Thesis Dissertation Defense

Abstract: Like most physical systems, the interaction characteristics among agents play an important role in active matter. For example, the extent of attraction can switch a collective of particles from a homogeneous mixture to phase-separated clusters; particle concavity in shape-changing active systems can change interactions from repulsive to attractive. The way that the force transmits can also be important. While many interactions transmit through direct or short-ranged contact (e.g., collisions or magnetic attraction), there are interactions that require the full description of the force-generating field to describe motion. These interactions can bring interesting features such as time delays, the coexistence of multiple length scales, and non-reciprocity, which are less common in short-ranged interacting systems. In this thesis, I will use several examples from my Ph.D. work to show the rich dynamics of active matter interacting through a field. Examples include active locomotors mimicking motion in curved space-time when driving on an elastic membrane, and resource-consuming agents driven by resource depletion that form different states of matter. Through these studies, I will also show how the connection between field-mediated interactions and classical fields allows us to explain and explore emergent phenomena in active matter using inspiration and tools from field theory. In addition to the study of field-mediated interactions, other studies of active matter with short-ranged interactions are presented in the later chapters. These include shape-changing active matter, the role of substrate curvature in active matter, and the analogy between attractive interaction in active matter and surface tension.