Dark archaeology: hunting for substructure and constraining cosmology

Many dark matter models predict small-scale substructure, including subhalos, boson stars, miniclusters, and primordial black holes. In this talk, I will discuss how gravitational microlensing serves as a powerful probe of these scenarios. I will describe the characteristic observational signals, and highlight how certain mass distributions — such as those associated with boson stars and some subhalos — produce distinctive features due to optical effects like caustics. I will explore opportunities for detecting these microlensing signatures using machine learning techniques, including real-time anomaly detection on time-series data from future surveys. Finally, I will discuss caustic crossings in giant arcs as a novel probe of subhalos, which can be used to derive constraints on the early Universe power spectrum.