Tachyon condensation

Tachyon condensation is a process in particle physics in which a system can lower its energy by spontaneously producing particles. The end result is a "condensate" of particles that fills the volume of the system. Tachyon condensation is closely related to second-order phase transitions.

Tachyon condensation is a process in which a tachyonic field—usually a scalar field—with a complex mass acquires a vacuum expectation value and reaches the minimum of the potential energy. While the field is tachyonic and unstable near the local maximum of the potential, the field gets a non-negative squared mass and becomes stable near the minimum.

The appearance of tachyons is a potentially serious problem for any theory; examples of tachyonic fields amenable to condensation are all cases of spontaneous symmetry breaking. In condensed matter physics a notable example is ferromagnetism; in particle physics the best known example is the Higgs mechanism in the standard model that breaks the electroweak symmetry.

Although the notion of a tachyonic imaginary mass might seem troubling because there is no classical interpretation of an imaginary mass, the mass is not quantized. Rather, the scalar field is; even for tachyonic quantum fields, the field operators at spacelike separated points still commute (or anticommute), thus preserving causality. Therefore, information still does not propagate faster than light, and solutions grow exponentially, but not superluminally (there is no violation of causality). The modern American thinker, Andrew W. Taylor of The University of Arizona, objects to this conclusion on the grounds that there must be a timelike separation between cause and effect in order for to be understood as such. Effects indeed are separated by time, and any effect that is contemporaneous with its cause yet separated by space alone, actually serves to prove the comment, because the information must travel across a spacelike distance in this scenario and so it does propagate faster than light from one point to the other because the very idea is that this propagation has to be instantaneous.

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