Tachyons, a mysterious variety of hypothetical particles capable of exceeding light speed, could play a more significant role in our understanding of the universe and its causal structure than scientists previously realized.
Not only have tachyons been revealed to be potentially compatible with Einstein’s special theory of relativity, but now, according to an international collaboration of physicists from the University of Warsaw and the University of Oxford, these curious particles could also help shed light on remaining questions regarding our understanding of the quantum world.
Exceeding the Universal Speed Limit
Tachyons, which derive their name from the Greek word tachýs, meaning fast or quick, are theorized to exist under conditions where their minimum speed would be the speed of light. This effectively means that they should only be capable of traveling at velocities that exceed this universally recognized speed limit.
Ordinary particles, by comparison, move at subluminal or slower than light speeds. As Einstein’s theory of relativity dictates, the universal laws of physics prevent anything from being capable of accelerating to the speed of light from a slower speed. The same isn’t necessarily true for tachyons, though, since they are theorized to be born at speeds that already exceed light. Hence, the opposite would seem to be the case for these unusual particles, which hypothetically should be incapable of slowing down to light speed or slower speeds.
The idea of such superluminal particles has its origins in theoretical studies conducted back in the 1960s by physicist Gerald Feinberg. Although no experimental evidence has ever confirmed their existence, a theoretical framework for how these proposed particles might come to be has been developed over the decades, occasionally resulting in some rather strange paradoxes.
Among these is a curiosity that arises from their superluminal travel speeds, which indicates that tachyons may effectively be capable of sending information backward in time, giving rise to bizarre conditions under which cause and effect could theoretically become reversed.
However, new research is revealing that despite the implications of their existence, these bizarre hypothetical particles may be compatible with the special theory of relativity and could also help offer physicists significant new insights into quantum theory.
The new findings could potentially also upend long-held notions about the unlikelihood of superluminal particles, suggesting that tachyons might even play a crucial role in the formation of matter.
Particles That Shouldn’t Exist
In the past, physicists had argued that tachyons were unlikely to exist since their field was thought to possess an unstable ground state, which would theoretically lead to so-called particle “avalanches.” Another argument against the existence of tachyons involves the notion that changes in the frame of reference of an observer would also seemingly change the number of particles they would see. This presents problems for physicists, since it would contradict our accepted ideas about how particle existence should remain independent of an observer.
A final conceptual hurdle for tachyons also involves how the energy of superluminal particles would be presumed to possess negative energy values, presenting further issues for physicists attempting to wrap their minds, as well as existing theories, around their existence.
In recent research by Jerzy Paczos, Kacper Dębski, Szymon Cedrowski, Szymon Charzyński, Krzysztof Turzyński, Andrzej Dragan with the University of Warsaw, and Artur Ekert from Oxford University, the physics team recognized that all these apparent challenges to the existence of tachyons can be derived from a common root problem.
Fundamentally, the team concluded, based on their research, that boundary conditions determining physical processes must be required to include the initial state, but also the final state of the system. Allowing this understanding to be incorporated into their theoretical framework led the team to a surprising discovery: each of the previously recognized constraints on the existence of tachyons could be resolved, allowing these hypothetical particles to become mathematically consistent despite their obvious strangeness.
Expanding the State Space for Tachyons
At the heart of the team’s work is an approach suggesting that for the probability of a quantum process involving tachyons to be calculated, both the past initial state as well as its future final state must be incorporated.
Incorporating this understanding into the theory, the researchers found that all previously cited difficulties disappeared, rendering current tachyon theories mathematically consistent. This approach suggests that in order to calculate the probability of a quantum process involving tachyons, one must consider both its past initial state and its future final state.
Andrzej Dragan, who specializes in quantum and relativistic physics and their oddities, as detailed in his book Unusually Special Relativity, notes that some of the apparent paradoxes that arise from the bizarre nature of tachyons are already staples of physics, despite sounding at times more like science fiction.
“The idea that the future can influence the present instead of the present determining the future is not new in physics,” Dragan says. “However, until now, this type of view has at best been an unorthodox interpretation of certain quantum phenomena, and this time we were forced to this conclusion by the theory itself.”
According to Dragan, making room for tachyons within existing theory essentially required he and his colleagues to first “expand the state space.”
The result, as outlined in the team’s study, marks the first time that the theory itself has necessitated such a view, resulting in an expanded “state space” that is mathematically able to accommodate tachyons.
Quantum Entanglement and Beyond
In addition to mathematically resolving the potential existence of tachyons, Dragan and the team’s research has also led to additional possibilities, such as a potentially new variety of quantum entanglement that could intermix the past and future, phenomena that are currently not accounted for in conventional particle theory.
Such ideas bear similarity to other recent discoveries involving how quantum entanglement might be capable of being used to effectively influence the past states of particles, which might effectively allow for the creation of quantum sensors capable of what some physicists liken to time travel.
Of particular intrigue is the discovery of a new kind of quantum entanglement, as suggested in Dragan and his colleagues’ research. This could mean that tachyons may be more than just mathematical constructs and could potentially also be observed.
Ultimately, tachyons could be recognized as essential components of the spontaneous symmetry-breaking process responsible for the formation of matter, thereby serving an important role in the fundamental structure of the universe.
The team’s new paper, “Covariant quantum field theory of tachyons,” was published in the journal Physical Review D on July 9, 2024.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.