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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| List of particles | 3/3 | https://en.wikipedia.org/wiki/List_of_particles | reference | science, encyclopedia | 2026-05-05T08:22:02.237050+00:00 | kb-cron |
== Auxiliary particles == Virtual particles are mathematical tools used in calculations that exhibits some of the characteristics of an ordinary particle but do not obey the mass-shell relation. These particles are unphysical and unobservable. These include:
Ghost particles, like Faddeev–Popov ghosts and Pauli–Villars ghosts Spurions, auxiliary field in a quantum field theory that can be used to parameterize any symmetry Soft photons, photons with energies below detectable in experiment. There are also instantons, field configurations which are a local minimum of the Yang–Mills field equation. Instantons are used in nonperturbative calculations of tunneling rates. Instantons have properties similar to particles, specific examples include:
Calorons, finite temperature generalization of instantons. Merons, a field configuration which is a non-self-dual solution of the Yang–Mills field equation. The instanton is believed to be composed of two merons. Sphalerons are a field configuration which is a saddle point of the Yang–Mills field equations. Sphalerons are used in nonperturbative calculations of non-tunneling rates. Renormalons, a possible type of singularity arising when using Borel summation. It is a counterpart of an instanton singularity.
== Classification by speed == A bradyon (or tardyon) travels slower than the speed of light in vacuum and has a non-zero, real rest mass. A luxon travels as fast as light in vacuum and has no rest mass. A tachyon is a hypothetical particle that travels faster than the speed of light so they would paradoxically experience time in reverse (due to inversion of the theory of relativity) and would violate the known laws of causality. A tachyon has an imaginary rest mass.
== See also ==
== References ==