Self-Energy

In quantum field theory, the self-energy of a particle is the contribution to its energy that arises from the particle own interaction with its own field; in electrostatics, for example, an electron is never truly free but is always interacting with its own electric field regardless of its surroundings. In condensed matter physics, self-energy effects create quasiparticles and give them a finite lifetime, and the concept is used to describe electron-electron interactions in Fermi liquids as well as phonon softening arising from electron-phonon coupling. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/