Manifestation of strange nonchaotic attractors in extended systems: A study through out-of-time-ordered correlators

The paper empirically defines and measures OTOC, vb, and FTLE for CMLs of quasiperiodically forced maps, documents nonchaotic suppression, chaotic ballistic spread, and persistent on–off spread in SNA, and proposes an empirical universal fit for VDLE λ(v) across regimes. These statements are well supported by the paper’s linearization (Eq. 7), definitions (Eqs. 4–6), parameter choices (α = 2.92/3.04/3.10 at ε′ = 0.76, κ = 0.5), heat maps and phase diagrams, and SNA diagnostics (FTLE distributions, phase sensitivity, partial Fourier sums, and 0–1 test) . The model gives a complementary, mechanistic derivation: Jn = A·Dn, a strict nearest-neighbor light-cone, and on the synchronous manifold a large-deviation formula λ(v) = Λsite − Iκ(v) that yields the butterfly/front speed from λ(v*) = 0 and explains vb ~ 2v* in chaotic regimes, with SNA producing on–off ballistic bursts despite Λsite < 0. This differs from the paper’s empirical cosh-fit (Eq. 8) but agrees in qualitative shape and small-v expansion; the empirical “universality” of fit parameters is naturally explained by the coupling kernel’s random-walk large deviations while the shift λ′ reflects Λsite. Thus, the paper’s empirical claims and the model’s theoretical derivation are consistent and complementary.