Proxemics is the study of the physical space between people. If you're interested in the way a city's density (the number of people who live in a certain area) affects its population, you might want to study proxemics.
Cultural anthropologists and sociologists sometimes study proxemics. This branch of knowledge looks at the distances between people in a few different ways, from the area you call your own (like your bedroom or apartment) to the space between you and others on a crowded elevator. When you look at proxemics, you can see the overlap with proximity — both words describe nearness, and come from the Latin proximus, "nearest or next."