Déjà-vu: a Sapienza-led team unveiled the physical origin of this phenomenon
Can, according to science, a past event reappear, as it seems to happen in the mysterious phenomenon of déjà-vu?
The answer is yes. This in itself is nothing new. A physical phenomenon analogous to that of the “already experienced” – known as Fermi-Pasta-Ulam recurrence − was discovered over sixty years ago by scientists Enrico Fermi, John Pasta and Stanislaw Ulam.
Now an international research group led by the Physics Department of Sapienza University of Rome has investigated the phenomenon in depth, obtaining an important result.
For the first time researchers have experimentally verified the phenomenon of recurrences in physics, demonstrating that their apparition can be explained through exact mathematical equations.
The results of the study – which also involved scientists from the Institute for Complex Systems of the National Research Council (CNR), Shenzhen University, Hebrew University of Jerusalem and Landau Institute for Theoretical Physics, were published in the journal Physical Review X.
The study of the phenomenon of recurrences in physics began after Enrico Fermi, while working on that complex calculation machine that would later become the modern computer, unexpectedly discovered that some complex systems, during their natural evolution, could spontaneously return to the starting point in a cyclical manner, without ever reaching a final equilibrium.
Now, the group coordinated by Sapienza University has demonstrated that the Fermi-Pasta-Ulam recurrence originates from a precise collective motion of the system and that this can be predicted, obtaining exact mathematical solutions from the model equations.
“These recurrent exact solutions imply an infinite number of ‘déjà-vus’ and have been recently formulated by Grinevich and Santini in the context of non-linear optical and hydrodynamic systems; however, the possibility of directly observing them was not a given”, explained Davide Pierangeli, corresponding author of the study.
The researchers reached their findings using a crystal made highly photosensitive by external electromagnetic fields. Thanks to an innovative experiment, they observed for the first time how specific optical waves can reappear during laser light propagation.
To date, none of the theoretical explanations to the famous Fermi-Pasta-Ulam problem had been experimentally confirmed, because recurrences in physics are a phenomenon highly sensitive to the minute fluctuations that characterize every natural system.
“The results of our study shed light on the fascinating and controversial Fermi-Pasta-Ulam problem and represent a cutting-edge test for nonlinear wave theory, thus opening the route to novel perspectives for forecasting the evolution of highly chaotic systems, as well as for controlling highly-concentrated energy flows of different natures, from tsunamis to plasmas to electromagnetic waves”, concluded Eugenio del Re, who coordinated the research team.