Physicists suggest that tachyons may be compatible with special relativity

Tachyons are hypothetical particles that travel faster than the speed of light. These superluminal particles are the “terrible baby” of modern physics. Until recently, they were generally considered entities that did not fit into special relativity.

However, a paper recently published in Physical examination D by physicists from the University of Warsaw and the University of Oxford has shown that many of these preconceptions were unfounded. Tachyons are not only not excluded from the theory, but allow us to better understand its causal structure.

Moving at speeds beyond the speed of light is one of the most controversial issues in physics. Hypothetical particles that can move at superluminal speeds, called tachyons (from the Greek tachýs – fast, fast), are the “terrible child” of modern physics. Until recently, they were widely regarded as creations that did not fit into the special theory of relativity.

At least three reasons for the non-existence of tachions within quantum theory were known until now. First: the ground state of the tachyon field was assumed to be unstable, which meant that such superluminal particles would form “avalanches”. Second: a change in the inertial observer was supposed to lead to a change in the number of particles observed in its frame of reference, yet the existence of, say, seven particles cannot depend on who is looking at them. The third reason: the energy of superluminal particles can take negative values.

Meanwhile, a group of authors: Jerzy Paczos, pursuing his Ph.D. at Stockholm University, Kacper Dębski, completing his Ph.D. at the Faculty of Physics, Szymon Cedrowski, final year student of Physics (English Studies) and four other experienced researchers: Szymon Charzyński, Krzysztof Turzyński, Andrzej Dragan (all from the Faculty of Physics, University of Warsaw) and Artur Ekert from the University of Oxford, have just pointed out that the difficulties with tachyons so far had a common cause. It turned out that the ‘boundary conditions’ that determine the course of physical processes include not only the initial state, but also the final state of the system.

Mixing the past and the future

Simply put: to calculate the probability of a quantum process involving tachyons, it is necessary to know not only its past initial state, but also its future final state. Once this fact was included in the theory, all the previously mentioned difficulties completely disappeared and the tachyon theory became mathematically stable.

“It’s a bit like online advertising – a simple trick can solve your problems,” says Andrzej Dragan, the main inspiration behind the entire research effort.

“The idea that the future can affect the present rather than the present determining the future is not new in physics. However, until now, this kind of view has been at best an unorthodox interpretation of some phenomena quantum, and this time we were forced to In this conclusion by the theory itself, in order to make “space” for the tachyons, we had to expand the state space”, concludes Dragani.

The authors also predict that expanding the boundary conditions has its own consequences: a new kind of quantum entanglement appears in the theory, mixing the past and the future, which is not present in conventional particle theory. The paper also raises the question of whether the tachyons thus described are merely a ‘mathematical possibility’ or whether such particles are likely to be observed one day.

According to the authors, tachyons are not only a possibility, but are, in fact, a necessary component of the spontaneous breaking process responsible for the formation of matter. This hypothesis would imply that the Higgs field excitations, before the symmetry was spontaneously broken, could travel at superluminal speeds in the vacuum.