What constitutes the dark matter? As the hunt for direct detection continues, theories abound. An intriguing proposal is due to Sikivie & Yang, who suggest that the dark matter is made up of a hypothetical particle called the axion, and in their picture the axionic dark matter forms an exotic gas known as a Bose-Einstein condensate due to gravitational thermalization. In this talk, I will discuss efforts to understand the Sikivie-Yang proposal, one of which spurred the development of a new framework for studying the Hamiltonian dynamics of gauge theories in curved spaces. I will also discuss the construction of a statistical mechanics for axion-like particles, which have very little interaction with photons.