Monopole fields from vortex sheets reconciling Abelian and center dominance

We describe a new order parameter for the confinement-deconfinement transition in lattice SU(2) Yang-Mills theory. It is expressed in terms of magnetic monopole field correlators represented as sums over sheets of center vortices. Our construction establishes a link between "abelian" and "center dominance". It avoids an inconsistency in the treatment of small scales present in earlier definitions of monopole fields by respecting Dirac's quantization condition for magnetic fluxes.Comment: LaTeX file, 6 pages; Lattice2001(plenary

Collective pairing of resonantly coupled microcavity polaritons

We consider the possible phases of microcavity polaritons tuned near a bipolariton Feshbach resonance. We show that, as well as the regular polariton superfluid phase, a "molecular" superfluid exists, with (quasi-)long-range order only for pairs of polaritons. We describe the experimental signatures of this state. Using variational approaches we find the phase diagram (critical temperature, density and exciton-photon detuning). Unlike ultracold atoms, the molecular superfluid is not inherently unstable, and our phase diagram suggests it is attainable in current experiments.Comment: paper (4 pages, 3 figures), Supplemental Material (7 pages, 8 figures

Unobserved Factor Utilization, Technology Shocks and Business Cycles

We derive a measure of technological change using firm-level panel data and controlling for imperfect competition, increasing returns and unobserved factor utilization. We show that the latter variable accounts for a relevant portion of the cyclicality of the Solow residual. Our key finding is that technological shocks result in a contraction of inputs on impact. Whilst this result is hard to reconcile with the transmission mechanism of real business cycle models, it is consistent with simple sticky-price models. Using survey information on the frequency and size of price revisions, we show that the evidence on the contractionary effects of technology shocks is indeed much stronger for firms with stickier prices.factor hoarding, technology shocks, business cycles

Energy Consumption, Survey Data and the Prediction of Industrial Production in Italy

We investigate the prediction of Italian industrial production. We first specify a model based on electricity consumption; we show that the cubic trend in such a model mostly captures the evolution over time of the electricity coefficient, which can be well approximated by a smooth transition model à la Terasvirta, with no gains in predictive power, though. We also analyze the performance of models based on data of different business surveys. According to basic statistics of forecasting accuracy, the linear energy-based model is not outperformed by any other single model, neither by a combination of forecasts. However, a more comprehensive set of evaluation criteria sheds light on the advantages of using the whole information available. Overall, the best forecasting performance is achieved by estimating a combined model which includes among regressors both energy consumption and survey data.Italy, industrial production, energy

Labor effort over the business cycle

Unobservable labor utilization is recognized as a crucial feature of economic fluctuations. Yet very little is known on the behavior of work effort over the business cycle. By using firm-level panel data drawn from two high-quality sources, we obtain a microeconomic estimate of variable labor effort from a dynamic cost minimization set-up. We argue that, contrary to common assumptions, the relationship between effort and hours is not monotonic. During a recovery, if a critical level of hours per capita is reached (say, because of labor market rigidities), every additional hour is worked with decreasing effort, due to physical fatigue. We provide supporting evidence by estimating the structural parameters of a Taylor approximation of the effort function. Corroborating evidence has been obtained by estimating the elasticity of effort with respect to hours at different business cycle conditions.labor effort, factor hoarding, business cycles

Pricing behavior and the comovement of productivity and labor: evidence from firm-level data

Recent contributions have suggested that technology shocks have a negative short-run effect on labor input, contrary to the predictions of standard flexible-price models of the business cycle. Some authors have interpreted this finding as evidence in favor of stickyprice models, while others have either augmented flexible-price models in a number of ways or disputed the empirical finding itself. In this paper we estimate a number of alternative measures of TFP growth for a representative sample of Italian manufacturing firms and find a negative impact of productivity shocks on labor input. Furthermore, by relying on the firmlevel reported frequency of price reviews, we find that the contractionary effect is strong for firms with stickier prices, but it is weaker or not significant for firms with more flexible prices, consistently with the prediction of sticky-price models.Productivity shocks, Labor input, price stickiness

Transition and the Fiscal Crisis in Central Europe

This paper argues that traditional explanations of the fiscal crisis in transition economies overlook the crucial interconnection between the reduction in subsidies expenditure and the decrease in profit tax revenues. It thus contends that the impact on the fiscal budget of the crisis of state-owned enterprises profitability has been largely overestimated in the literature. The net contribution to the government budget from the enterprise sector - defined as profit taxes net of cross-subsidization - has increased during the transition in Poland and Czechoslovakia, and has remained constant in Hungary. After reexamining the data, it is argued that - while it is undoubtable that the prospects for fiscal revenues are worrisome - the main determinant of the fiscal crisis is to the explosion of social security expenditures. The paper also assesses the applicability of these results to other former socialist economies.Poland, Hungary, Czechoslovakia, Eastern Europe, Socialist economies, economic transition, fiscal crisis, revenue crisis, social expenditures, pensions

Interpreting the Procyclical Productivity of Manufacturing Sectors: Can We Really Rule Out External Effects:

Explaining procyclical productivity is crucial for any theory of the business cycle. Recent contributions have focused on the dynamic implications of persistent aggregate fluctuations on sectoral productivity. Given a permanent innovation in aggregate output, variations of labor (or capital) utilization may have only a transitory effect on measured productivity, whereas external effects should produce permanent effects. We find that persistent aggregate fluctuations have a permanent effect on sectoral productivity of four-digit U.S. manufacturing industries. We discuss a number of alternative explanations of this evidence. Whereas our findings are unlikely to be due to market power and increasing returns, they are consistent with simple models with external effects or temporal agglomeration.

Topological Sound and Flocking on Curved Surfaces

Active systems on curved geometries are ubiquitous in the living world. In the presence of curvature orientationally ordered polar flocks are forced to be inhomogeneous, often requiring the presence of topological defects even in the steady state due to the constraints imposed by the topology of the underlying surface. In the presence of spontaneous flow the system additionally supports long-wavelength propagating sound modes which get gapped by the curvature of the underlying substrate. We analytically compute the steady state profile of an active polar flock on a two-sphere and a catenoid, and show that curvature and active flow together result in symmetry protected topological modes that get localized to special geodesics on the surface (the equator or the neck respectively). These modes are the analogue of edge states in electronic quantum Hall systems and provide unidirectional channels for information transport in the flock, robust against disorder and backscattering.Comment: 15 pages, 6 figure