Stefano Ruffo - ISC-CNR Sesto Fiorentino and SISSA, Trieste
Wednesday, November 5th, 2025
Zoom opens: 10:30AM EST
Seminar begins: 10:45AM EST
Burgers equation and the Fermi-Pasta-Ulam-Tsingou lattice
The study of thermalisation in isolated systems was pioneered by Fermi-Pasta-Ulam-Tsingou (FPUT). In this talk I will present a new avenue towards the understanding of thermalisation, the presence of a power-law in the Fourier energy spectrum. A universal scaling exponent is obtained by mapping the FPUT model onto a pair of Burgers equations. Energy is transferred to higher Fourier modes like in “Burgers turbulence”, while ``shocks” develop on the lattice. Only at much longer times the system reaches energy equipartition. I will present new analytical results enabling the derivation of the average shock-time for general random initial conditions.
References:
-M. Gallone, M. Marian, A. Ponno and S. Ruffo:"Burgers turbulence in the FPUT chain", Phys. Rev. Lett.
114101 (2023)
-M. Gallone, A. Ponno and S. Ruffo:"Energy cascade and Burgers turbulence in the FPUT chain", Phys. Rev. E, 054212 (2024)
-M. Gallone, R. Grande, A. Ponno, S. Ruffo and E. Druais: "Random initial data and average shock time in the Fermi-Pasta-Ulam-Tsingou chain", work in progress (2025)