Superluminal motion remains one of physics' most debated topics. Tachyons, derived from the Greek word tachys meaning fast or quick, were seen as theoretical misfits in special relativity. Previously, three major arguments against tachyons within quantum theory existed. First, the ground state of the tachyon field was believed to be unstable, leading to particle avalanches. Second, the observer's reference frame was thought to alter the perceived number of particles, an inconsistency in quantum theory. Third, the energy of superluminal particles could assume negative values.
A team of researchers, including Jerzy Paczos from the University of Stockholm, Kacper Debski from the Faculty of Physics, Szymon Cedrowski, a final-year physics student, and seasoned physicists Szymon Charzynski, Krzysztof Turzynski, Andrzej Dragan from the University of Warsaw, and Artur Ekert from Oxford University, identified a common issue underlying these problems. They discovered that 'boundary conditions' in physical processes include both the initial and final states of the system. Their findings, published in Physical Review D, indicate that incorporating future final states into the theory resolves previous inconsistencies, making tachyon theory mathematically sound.
"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," the researchers explain. Incorporating this into the theory eliminates the previous difficulties and renders the tachyon theory coherent.
"It's a bit like internet advertising - one simple trick can solve your problems," says Andrzej Dragan, chief inspirer of the whole research endeavour. "The idea that the future can influence the present instead of the present determining the future is not new in physics. 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. To 'make room' for tachyons we had to expand the state space," concludes Dragan.
The researchers also predict that expanding boundary conditions introduces a new type of quantum entanglement, intertwining past and future, absent in conventional particle theory. The paper explores whether tachyons are purely theoretical or if they might be observed one day. According to the authors, tachyons are not only plausible but crucial for the spontaneous breaking process that forms matter. They suggest that Higgs field excitations, before symmetry breaking, could travel at superluminal speeds in a vacuum.
Research Report:Covariant quantum field theory of tachyons
