  We investigate the equilibration process of the strongly coupled quartic
Fermi-Pasta-Ulam-Tsingou (FPUT) model by adding Langevin baths to the ends of
the chain. The time evolution of the system is investigated by means of
extensive numerical simulations and shown to match the results expected from
equilibrium statistical mechanics in the time-asymptotic limit. Upon increasing
the nonlinear coupling, the thermalization of the energy spectrum displays an
increasing asymmetry in favour of small-scale, high-frequency modes, which
relax significantly faster than the large-scale, low-frequency ones. The global
equilibration time is found to scale linearly with system size and shown to
exhibit a power-law decay with the strength of the nonlinearity and
temperature. Nonlinear interaction adds to energy distribution among modes,
thus speeding up the thermalization process.
