Self-force via energy–momentum and angular momentum balance equations

The radiation reaction for a pointlike charge coupled to a massive scalar field is considered. The retarded Green's function associated with the Klein–Gordon wave equation has support not only on the future light cone of the emission point (direct part) but extends inside the light cone as well (tail part). Dirac's scheme of decomposition of the retarded electromagnetic field into the “mean of the advanced and retarded field” and the “radiation” field is adapted to theories where Green's function consists of the direct and the tail parts. The Harish-Chandra equation of motion of radiating scalar charge under the influence of an external force is obtained. This equation includes effect of particle's own field. The self-force produces a time-changing inertial mass.