Improved exponential stability for near-integrable quasi-convex Hamiltonians

In this article, we improve previous results on exponential stability for analytic and Gevrey perturbations of quasi-convex integrable Hamiltonian systems. In particular, this provides a sharper upper bound on the speed of Arnold diffusion which we believe to be optimal

Remarks on step cocycles over rotations, centralizers and coboundaries

By using a cocycle generated by the step function $\varphi_{\beta, \gamma} = 1_{[0, \beta]} - 1_{[0, \beta]} (. + \gamma)$ over an irrational rotation $x \to x + \alpha \mod 1$, we present examples which illustrate different aspects of the general theory of cylinder maps. In particular, we construct non ergodic cocycles with ergodic compact quotients, cocycles generating an extension $T_{\alpha, \varphi}$ with a small centralizer. The constructions are related to diophantine properties of $\alpha, \beta, \gamma$

Implicit tax co-ordination under repeated policy interactions

In the context of a stylised gaine theoretical framework of capital tax competition, we show that when repeated policy interactions are associated to a systematic punishment of the deviating policymaker, a coordinated outcome can be the solution to the non cooperative tax game. This resuit suggests that explicit forms of policy coordination, such as a centralised tax authority, could in fact be largely unnecessary.Policy coordination, international fiscal issues

Implicit tax co-ordination under repeated policy interactions

In the context of a stylised game theoretical framework of capital tax competition, we show that when repeated policy interactions are associated to a systematic punishment of the deviating policymaker, a co-ordinated outcome can be the solution to the non co-operative tax game. This result suggests that explicit forms of policy co-ordination, such as a centralised tax authority, could in fact be largely unnecessary. JEL Classification: E61, H87International Fiscal Issues, Policy Co-ordination