Nonequilibirum steady state for harmonically-confined active particles

We study the full nonequilibirum steady state distribution $P_{\text{st}}\left(X\right)$ of the position $X$ of a damped particle confined in a harmonic trapping potential and experiencing active noise, whose correlation time ${\tau }_c$ is assumed to be very short. Typical fluctuations of $X$ are governed by a Boltzmann distribution with an effective temperature that is found by approximating the noise as white Gaussian thermal noise. However, large deviations of $X$ are described by a non-Boltzmann steady-state distribution. We find that, in the limit ${\tau }_c\to 0$, they display the scaling behavior $P_{\text{st}}\left(X\right)\sim e^{-s\left(X\right)\mathrm{/}{\tau }_c}$, where $s\left(X\right)$ is the large-deviation function. We obtain an expression for $s\left(X\right)$ for a general active noise, and calculate it exactly for the particular case of telegraphic (dichotomous) noise.