selfinteraction

Self-interaction is the interaction of a system with its own field, charge distribution, or influence, rather than with external objects. It appears in multiple branches of physics and related disciplines, often manifesting as self-energy, self-force, or self-consistent fields. The concept is used to describe both concrete physical effects and formal artifacts of approximate theories.

In classical electrodynamics, a charged particle generates an electromagnetic field that can exert a force on the particle itself, leading to a self-force known as radiation reaction. The resulting equations (for example, the Abraham–Lorentz–Dirac equation) raise conceptual and mathematical challenges, including infinities for idealized point charges. These issues motivate mass renormalization and careful treatment of extended charge distributions.

In quantum field theory, self-interaction is ubiquitous through loop corrections: particles can emit and reabsorb virtual quanta, modifying their propagation and interactions. Self-energy and vacuum polarization are common examples, and renormalization techniques are used to absorb divergences into redefined physical parameters.

In chemistry and materials science, self-interaction often refers to the self-interaction error in approximate electronic structure methods, notably density functional theory with local or semi-local functionals. This error causes spurious self-repulsion and artificial electron delocalization. It is mitigated by self-interaction correction schemes or by using hybrid functionals that incorporate exact exchange.

In practice, handling self-interaction requires careful modeling to separate genuine self-effects from artifacts of the chosen theoretical framework. The topic informs both foundational physics and practical computational methodologies.