Back-reaction
Encyclopedia
In theoretical physics
, Back-reaction is often necessary to calculate the behavior of a particle
or an object in an external field.
When the particle is considered to be infinitely light or have an infinitesimal
charge, it is said that we deal with a probe and the back-reaction is neglected. However, a real object also carries a mass and charges itself.
They modify the original environment (for example, they help to curve the space in general relativity
) and this modification - the back-reaction - has to be taken into account when a more accurate calculation is performed.
In Cosmology the term Back-reaction is used for the measure of the non commutativity of the averaging procedure and the dynamical evolution of space-time. The existence of an isotropy scale is determined be the legth scale at which the Back-reaction parameter vanishes. The existence of such scale still needs experimental confirmation.
Theoretical physics
Theoretical physics is a branch of physics which employs mathematical models and abstractions of physics to rationalize, explain and predict natural phenomena...
, Back-reaction is often necessary to calculate the behavior of a particle
Elementary particle
In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...
or an object in an external field.
When the particle is considered to be infinitely light or have an infinitesimal
Infinitesimal
Infinitesimals have been used to express the idea of objects so small that there is no way to see them or to measure them. The word infinitesimal comes from a 17th century Modern Latin coinage infinitesimus, which originally referred to the "infinite-th" item in a series.In common speech, an...
charge, it is said that we deal with a probe and the back-reaction is neglected. However, a real object also carries a mass and charges itself.
They modify the original environment (for example, they help to curve the space in general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...
) and this modification - the back-reaction - has to be taken into account when a more accurate calculation is performed.
In Cosmology the term Back-reaction is used for the measure of the non commutativity of the averaging procedure and the dynamical evolution of space-time. The existence of an isotropy scale is determined be the legth scale at which the Back-reaction parameter vanishes. The existence of such scale still needs experimental confirmation.