(redirected from Tachyons)
Also found in: Dictionary.


(tăk`ēŏn'), hypothetical elementary particleelementary particles,
the most basic physical constituents of the universe. Basic Constituents of Matter

Molecules are built up from the atom, which is the basic unit of any chemical element. The atom in turn is made from the proton, neutron, and electron.
..... Click the link for more information.
 that travels only at speeds exceeding that of light. According to the theory of relativityrelativity,
physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.
..... Click the link for more information.
, the speed of light is the limiting velocity for all ordinary material particles. Particles having nonzero rest mass can approach, but not reach, the speed of light, since their mass would become infinite at that speed. On the other hand, particles with zero rest mass, such as the photonphoton
, the particle composing light and other forms of electromagnetic radiation, sometimes called light quantum. The photon has no charge and no mass. About the beginning of the 20th cent.
..... Click the link for more information.
, must always travel at the speed of light; they cannot be brought to rest or even slowed down. Theorists have argued that since nothing in principle prohibits the existence of a third class of particles that travel only at speeds exceeding that of light, such particles, called tachyons [Gr. tachys,=swift] may exist although no evidence for them has been found. In the terminology of the theory, the particles that travel only at the speed of light are called luxons, and those that travel at lesser speeds are called tardyons. Like the original theory of relativity, the theory of tachyons has several aspects that appear to contradict common sense but that are fully self-consistent. For example, a tachyon must have an imaginary (in the mathematical sense) rest mass, or proper mass, and it must travel faster rather than slow down when it loses energy.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/


A hypothetical faster-than-light particle consistent with the special theory of relativity. According to this theory, a free particle has an energy E and a momentum p which form a Lorentz four-vector. The length of this vector is a scalar, having the same value in all inertial reference frames. One writes

Eq. (1), where c is the speed of light and the parameter m2 is a property of the particle, independent of its momentum and energy. Three cases may be considered: m2 may be positive, zero, or negative. The case m2 > 0 applies for atoms, nuclei, and the macroscopic objects of everyday experience. The positive root m is called the rest-mass. If m2 = 0, the particle is called massless. A few of these are known: the electron neutrino, the muon neutrino, the photon, and the graviton. The name tachyons (after a Greek word for swift) has been given to particles with m2 < 0.

In general, the particle speed is given by Eq. (2). If m2 < 0,

Eq. (1) implies E > c p and Eq. (2) gives v < c. If m2 = 0, then E = c p and v = c. In case m2 < 0, one finds E < c p and v > c. Tachyons exist only at faster-than-light speeds. See Elementary particle, Relativity

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.


(particle physics)
A hypothetical particle that travels faster than light, consistent with the theory of relativity.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
As the scalar waves being studied belong to the massive scalar tachyons, the corresponding KGE is given by
Faster-than-light inertial frames, interacting tachyons and tadpoles.
8, they appear to move faster than light as tachyons and thereby constitute the framework for both annihilation and creation processes, as was so elegantly presented by Richard Feynman; it is the ability of a tachyonic or virtual process occurring between two scattering events, say A and B, that made particles of matter going backward in time with negative energy and faster-than-light going from A to B appear as antiparticles going faster than light with positive energy and forward in time going from B to A.
Putting all this together I have surmised that those of us with the klutz factor (let's call it K Factor) have somehow acquired too many neutrinos and, quite possibly, tachyons too, and are therefore going around ever-so-slightly ahead of ourselves.
I offer to expand some physical terms, such as local time, spatial-temporal continuum, action quantum, light velocity, photon, tachyon, inertial mass onto the phenomena traditionally described by the concepts within ecology, environmental sciences, and societal ecology as well.
In the example that I have given, there seems to be something anemic and redundant about the tachyons. The tachyons do not genuinely influence anything else that goes on in the world.
Despite the fact that on today tachyons (ie objects moving at a velocity greater than the velocity of light) are not experimentally detected, this subject remains being actual.
MNT gD-brane [17] is simply given by a sum of two "tachyons":
Kirzlmits [38]: "Not quite simple and rather obscure relations between the concept of 'instability' and 'tachyons' are discussed".
After early attempts at the construction of tachyonic neutrino theories [1-7], progress in the theoretical development was hindered by difficulties in the construction of a viable field theory involving tachyons (a particularly interesting argument was presented in [8]).
A similar theory of tachyons in the framework of Special Relativity was suggested, independently of Tanglerlini, in 1979 by Torgny Sjodin [7] (he was a Swedish scientist working in Theoretical Physics Department at Vrije Universiteit in Brussels).
It resolves the ordering ambiguities in QFT, the problem of time in Cosmology and admits superluminal propagation (tachyons) without violations of causality.