Validity Condition for Normal Form Transformation in β‑FPUT

The β‑FPUT normal‑form transformation is valid when β ≪ 1/N^{1+ε} (ε>0), i.e., β N must stay small. Simulations in equilibrium and out‑of‑equilibrium confirm the scaling. getnews.me/validity-condition-for-n... #betafput #normalform