  Unlike equilibrium systems, active matter is not governed by the conventional
laws of thermodynamics. Through a series of analytic calculations and Langevin
dynamics simulations, we explore how systems cross over from equilibrium to
active behavior as the activity is increased. In particular, we calculate the
profiles of density and orientational order near straight or circular walls,
and show the characteristic width of the boundary layers. We find a simple
relationship between the enhancements of density and pressure near a wall.
Based on these results, we determine how the pressure depends on wall
curvature, and hence make approximate analytic predictions for the motion of
curved tracers, as well as the rectification of active particles around small
openings in confined geometries.
