Deviation of ergodic averages for rational polygonal billiards

We prove polynomial upper bounds for the deviation of ergodic averages for the straight line flow on every translation surface in almost every direction, in particular for those surfaces arising from rational polygonal billiards.Comment: to appear in Duke Mathematical Journal. Some minor corrections made, typos fixed, some new references adde

Mixing Flows on Moduli Spaces of Flat Bundles over Surfaces

We extend Teichmueller dynamics to a flow on the total space of a flat bundle of deformation spaces of representations of the fundamental group of a fixed surface S in a Lie group G. The resulting dynamical system is a continuous version of the action of the mapping class group of S on the deformation space. We observe how ergodic properties of this action relate to this flow. When G is compact, this flow is strongly mixing over each component of the derormation space and of each stratum of the Teichmueller unit sphere bundle over the Riemann moduli space. We prove ergodicity for the analogous lift of the Weil-Petersson geodesic local. flow.Comment: 18 pages, no figures, presented at the Oxford conference honoring Nigel Hitchin's 70th birthday (9 September 2016) and to appear in the companion volume published by Oxford University Pres

Macroeconomic Shocks and the Business Cycle: Evidence from a Structural Factor Model

We use a dynamic factor model to provide a semi-structural representation for 101 quarterly US macroeconomic series. We find that (i) the US economy is well described by a number of structural shocks between two and six. Focusing on the four-shock specification, we identify, using sign re- strictions, two non-policy shocks, demand and supply, and two policy shocks, monetary and fiscal. We obtain the following results. (ii) Both supply and demand shocks are important sources of fluc- tuations; supply prevails for GDP, while demand prevails for employment and inflation. (ii) Policy matters, Both monetary and fiscal policy shocks have sizeable effects on output and prices, with little evidence of crowding out; both monetary and fiscal authorities implement important system- atic countercyclical policies reacting to demand shocks. (iii) Negative demand shocks have a large long-run positive effect on productivity, consistently with the Schumpeterian "cleansing" view of recessions.structural factor model, sign restrictions, monetary policy, fiscal policy, demand, supply

Employment in the Public Sector

This paper presents a model of wage-employment determination in private and public sectors, which allows us to analyze the effects of different institutional arrangements on labor market equilibria. In particular, it focuses on how different degrees of coordination in decision processes affect hiring and wage setting outcomes. Cooperation in unions’ behavior results in wage increases and employment reduction in the private sector, whereas it induces wage moderation and employment expansion in the public sector. Not surprisingly, if public decision units do not fully internalize the aggregate budget constraint in their hiring processes, the public sector wage bill and the level of taxation increase, thus enhancing the crowding out effect on private employment. Such effect appears to be stronger in the presence of encompassing union behavior. An empirical analysis performed on a sample of OECD countries in the period 1960-2000 seems to support the main predictions of the model.public employment, wage bargaining, decentralization