Calorimetry for active systems

(Thermal) active systems are in physical contact with (at least) two reservoirs: one which is often chemical or radiative and source of low entropy, and one which can be identified with a thermal bath or environment in which energy gets dissipated. Perturbing the temperature, the heat capacity measures the excess heat in addition to the steady ever-existing dissipation. Simulating AC-calorimetry, we numerically evaluate the heat capacity for run-and-tumble particles in double-well and periodic potentials. Low-temperature Schottky-like peaks show the role of activity and indicate shape transitions, while regimes of negative heat capacity appear at higher propulsion speeds.Comment: 16 pages, 6 figure