  In 1955, Fermi, Pasta, Ulam, and Tsingou reported recurrence over time of
energy between modes in a one-dimensional array of nonlinear oscillators.
Subsequently, there have been myriad numerical experiments using homogenous
FPUT arrays, which consist of chains of ideal, nonlinearly-coupled oscillators.
However, inherent variations --- e.g., due to manufacturing tolerance ---
introduce heterogeneity into the parameters of any physical system. We
demonstrate that such tolerances degrade the observance of recurrence, often
leading to complete loss in moderately sized arrays. We numerically simulate
heterogeneous FPUT systems to investigate the effects of tolerances on
dynamics. Our results illustrate that tolerances in real nonlinear oscillator
arrays may limit the applicability of results from numerical experiments on
them to physical systems, unless appropriate heterogeneities are taken into
account.
