Sharp convergence rates for the vanishing discount problem with hyperbolic Aubry sets

Abstract: Let $H\in C<sup>2(T<sup>*M)$ be a Tonelli Hamiltonian on a closed connected manifold and let $u_λ$ solve [ λu_λ+H(x,Du_λ)=c(H)\qquad\text{in }M. ] We study the convergence rate of $u_λ$ to the selected critical solution $u_0$. Assume that the lifted Aubry set is a finite union $\widetilde{A}=Γ<em>1\sqcup\cdots\sqcupΓ_N$, where each $Γ_i$ is either a hyperbolic equilibrium or a periodic orbit hyperbolic in the critical energy level. We prove [ -Cλ\le uλ-u_0\le Cλ|\logλ|. ] Let $μ<em>i$ be the projected Mather measure associated with $Γ_i$. If [ \int_M u_0\,\mathrm dμ_i=0\qquad \text{for every }i, ] then [ |uλ-u_0|_\infty\le Cλ. ] In particular, if the lifted Aubry set consists of a single hyperbolic equilibrium or a single hyperbolic periodic orbit, the convergence rate is $O(λ)$. We give examples showing that both convergence rates $O(λ)$ and $O(λ|\logλ|)$ are optimal. Without hyperbolicity, finite-order degenerate examples give lower bounds of order $λ<sup>{1/(2r-1)}$ with $r\ge2$. We also construct infinite-order degenerate examples with arbitrarily slow convergence. Taken together, these results provide, to our knowledge, the first systematic quantitative theory for the vanishing discount problem in the Tonelli setting.