Revisiting the Equation of State of Active Brownian Particles

One of the unique feature of active systems is that they are able to phase separate without the presence of attractive interparticle interactions. Determining quantitatively the phase boundary for these fundamentally out-of-equilbrium systems is an on-going challenge within the community. The mechanically defined active pressure plays a central role in many of the recently proposed coexistence criteria. Using a combination of large-scale simulation and analytical theory, we reveal previously unknown features of this equation of state. Recognizing these features is essential when attempting to assess coexistence criteria by comparing the predicted phase diagram to simulation data. Upon using this refined equation of state, the predicted phase boundaries are qualitatively altered in comparison to previously work.