In most
theoretical physics such as
quantum field theory, a particle's
self-energy ![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=2188)
represents the contribution to the particle's
energy, or
effective mass, due to interactions between the particle and the system it is part of. For example, in
electrostatics the self-energy of a given charge distribution is the energy required to assemble the distribution by bringing in the constituent charges from infinity, where the electric force goes to zero. In a
condensed matter context relevant to electrons moving in a material, the self-energy represents the potential felt by the electron due to the surrounding medium's interactions with it: for example, the fact that electrons repel each other means that a moving electron polarizes (causes to displace) the electrons in its vicinity and this in turn changes the potential the moving electron feels; these and other effects are included in the self-energy. In basic terms, the self-energy is the energy that a particle has as a result of changes that it itself causes in its environment.