Peter H Baxendale | Searcharxiv

arXiv2026

Instability of a nonlinear oscillator with small friction and small additive noise

Let $λ= λ(β,σ,a,b)$ denote the top Lyapunov exponent for the linearization along trajectories of the noisy damped non-linear oscillator $\ddot{x}+β\dot{x} + ax+bx^3 = σ\dot{W}_t$, where $a$, $b$ and $β$ are all positive and $σ\neq 0$. In 2004 Arnold, Imkeller and Sri Namachchivaya stated without proof that $λ(\varepsilon^2 β,\varepsilon σ,a,b) \sim \overlineλ \varepsilon^{2/3}$ as $\varepsilon \to 0$ with $\overlineλ > 0$. This paper contains a proof of this assertion.

math.PR↗

arXiv2025

Moment stability and large deviations for random dynamical systems on non-compact manifolds

The rate function for large deviations of the finite time Lyapunov exponent for the derived process in TM corresponding to a stochastic differential equation in M is related, via the Gartner-Ellis theorem, to the p-th moment Lyapunov exponent. When M is compact there is a characterization of the p-th moment Lyapunov exponent in terms of an eigenvalue problem for an associated differential operator acting on functions on the unit sphere bundle SM. For the non-compact case, we formulate growth conditions which, together with standard assumptions of hypoellipticity and positivity, ensure that the eigenvalue characterization remains valid so long as the corresponding eigenfunction is restricted to be in a suitable function space. There is a central limit theorem for finite time Lyapunov exponent, and there are moderate deviation estimates for the finite time Lyapunov exponent, both involving the second derivative of the moment exponent function at 0.

math.DS↗