# Flat trace statistics of the transfer operator of a random partially expanding map

## TL;DR

This paper studies the statistical behavior of the transfer operator associated with a randomly perturbed expanding map on the circle, revealing that its flat traces follow a normal distribution in the semiclassical limit up to a logarithmic Ehrenfest time.

## Contribution

It demonstrates that the flat traces of the transfer operator exhibit Gaussian fluctuations in the semiclassical limit for a class of random partially expanding maps.

## Key findings

- Flat traces behave as normal distributions in the semiclassical limit.
- Behavior holds up to the Ehrenfest time proportional to log of frequency.
- Results extend understanding of transfer operators in random dynamical systems.

## Abstract

We consider the skew-product of an expanding map $E$ on the circle $\mathbb T$ with an almost surely $\mathcal C^k$ random perturbation $\tau=\tau_0+\delta\tau$ of a deterministic function $\tau_0$: \[F :\left\{\begin{array}{rcl} \mathbb T \times \mathbb R & \longrightarrow & \mathbb T \times \mathbb R\\ (x,y)& \longmapsto & (E(x), y+\tau(x))\\ \end{array} \right.\] The associated transfer operator $\mathcal L:u \in \mathcal C^k (\mathbb T \times \mathbb R) \mapsto u\circ F$ can be decomposed with respect to frequency in the $y$ variable into a family of operators acting on functions on the circle: \[\mathcal L_\xi :\left\{\begin{array}{rcl} \mathcal C^k(\mathbb T) & \longrightarrow & \mathcal C^k(\mathbb T)\\ u & \longmapsto & e^{i\xi\tau}u\circ E \\ \end{array} \right.\] We show that the flat traces of $\mathcal L^n_{\xi}$ behave as normal distributions in the semiclassical limit $n, \xi\to\infty$ up to the Ehrenfest time $n\leq c_k\log\xi$.