Fermi-Pasta-Ulam-Tsingou Problem

The Fermi-Pasta-Ulam-Tsingou (FPUT) problem, formerly the Fermi-Pasta-Ulam problem, was the apparent paradox in chaos theory that many sufficiently complicated physical systems exhibited almost exactly periodic behavior, called Fermi-Pasta-Ulam-Tsingou recurrence, instead of the ergodic behavior expected under the equipartition theorem. Enrico Fermi and his collaborators had expected the modeled system to thermalize quickly, with all vibrational modes eventually appearing with equal strength, so the observed recurrence came as a surprise; over much longer time periods the system does eventually thermalize, and multiple competing explanations for the behavior remain a topic of active research. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/