On the convergence to equilibrium of unbounded observables under a family of intermittent interval maps

Abstract: We consider a family ${ T_{r} \colon [0, 1] \circlearrowleft }{r \in [0, 1]}$ of Markov interval maps interpolating between the Tent map $T{0}$ and the Farey map $T_{1}$. Letting $\mathcal{P}{r}$ denote the Perron-Frobenius operator of $T{r}$, we show, for $\beta \in [0, 1]$ and $\alpha \in (0, 1)$, that the asymptotic behaviour of the iterates of $\mathcal{P}{r}$ applied to observables with a singularity at $\beta$ of order $\alpha$ is dependent on the structure of the $\omega$-limit set of $\beta$ with respect to $T{r}$. Having a singularity it seems that such observables do not fall into any of the function classes on which convergence to equilibrium has been previously shown.