Virtual particle
In quantum field theory, forces—such as the electromagnetic repulsion or attraction between two charges—can be thought of as resulting from the exchange of virtual photons between the charges.
Virtual particles are also excitations of the underlying fields, but are "temporary" in the sense that they appear in calculations of interactions, but never as asymptotic states or indices to the scattering matrix.
The accuracy and use of virtual particles in calculations is firmly established, but as they cannot be detected in experiments, deciding how to precisely describe them is a topic of debate.
[5] Although widely used, they are by no means a necessary feature of QFT, but rather are mathematical conveniences — as demonstrated by lattice field theory, which avoids using the concept altogether.
Such calculations are often performed using schematic representations known as Feynman diagrams, in which virtual particles appear as internal lines.
[6]: 119 The probability amplitude for a virtual particle to exist tends to be canceled out by destructive interference over longer distances and times.
[9] Written in the usual mathematical notations, in the equations of physics, there is no mark of the distinction between virtual and actual particles.
However, in the case of photons, power and information transfer by virtual particles is a relatively short-range phenomenon (existing only within a few wavelengths of the field-disturbance, which carries information or transferred power), as for example seen in the characteristically short range of inductive and capacitative effects in the near field zone of coils and antennas.
Some field interactions which may be seen in terms of virtual particles are: Most of these have analogous effects in solid-state physics; indeed, one can often gain a better intuitive understanding by examining these cases.
Examples of macroscopic virtual phonons, photons, and electrons in the case of the tunneling process were presented by Günter Nimtz[11] and Alfons A.
The appeal of the Feynman diagrams is strong, as it allows for a simple visual presentation of what would otherwise be a rather arcane and abstract formula.
This implies the number of particles in an area of space is not a well-defined quantity but, like other quantum observables, is represented by a probability distribution.
In short, the vacuum of a stationary frame appears, to the accelerated observer, to be a warm gas of actual particles in thermodynamic equilibrium.
If, for example, a pair of atomic nuclei are merged to very briefly form a nucleus with a charge greater than about 140, (that is, larger than about the inverse of the fine-structure constant, which is a dimensionless quantity), the strength of the electric field will be such that it will be energetically favorable[further explanation needed] to create positron–electron pairs out of the vacuum or Dirac sea, with the electron attracted to the nucleus to annihilate the positive charge.
Electromagnetic radiation consists of real photons which may travel light years between the emitter and absorber, but (Coulombic) electrostatic attraction and repulsion is a relatively short-range[dubious – discuss] force that is a consequence of the exchange of virtual photons [citation needed].
