Multiplicity of layered solutions for Allen-Cahn systems with symmetric double well potential

We study the existence of solutions $u:\R^{3}\to\R^{2}$ for the semilinear elliptic systems \begin{equation}\label{eq:abs} -\Delta u(x,y,z)+\nabla W(u(x,y,z))=0, \end{equation} where $W:\R^{2}\to\R$ is a double well symmetric potential. We use variational methods to show, under generic non degenerate properties of the set of one dimensional heteroclinic connections between the two minima \a_{\pm} of $W$, that (\ref{eq:abs}) has infinitely many geometrically distinct solutions $u\in C^{2}(\R^{3},\R^{2})$ which satisfy u(x,y,z)\to \a_{\pm} as ${x\to\pm\infty}$ uniformly with respect to $(y,z)\in\R^{2}$ and which exhibit dihedral symmetries with respect to the variables $y$ and $z$. We also characterize the asymptotic behaviour of these solutions as $|(y,z)|\to +\infty$

Is Russia restructuring ? new evidence on job creation and destruction

The authors explorethe labor dynamics of Russian enterprise restructuring, empirically assessing how patterns of job creation and destruction are related to various aspects of enterprise restructuring across firms in different sectors and regions, and to different forms, sizes, vintages, and performance characteristics of ownership. Evidence from case studies - based on more than 50 site visits in 2000 - suggests that jobs have been destroyed, but only to a limited degree in some sectors and regions, largely because of institutional and incentive constraints and a still-widespread"socialist"corporate culture. Jobs have been created - particularly in sectors where devaluation had the most pronounced effect on important substitution and export promotion - but only slowly, mostly for lack of skilled workers and because regional mobility is limited. Labor turnover appears higher within regions than across regions. Newly available data for 1996 - 99 (provided by Goskomstat) for about 128,000 enterprises in 24 industrial sectors in Russia's 89 regions indicates that the typical firm has experienced only modest downsizing - about 12 percent - in number of employees. Smaller firms have entered, and larger, mature businesses have exited some sectors. Except for a lull in 1998, the rate of job creation has steadily increased and the rate of job destruction has declined, dropping substantially in 1998 - 99."Voluntary"worker separations remain the main - and growing - form of layoff, and the proportion of layoffs through redundancies is shrinking (now about 4 percent of total separations). Firm size and net employment growth are not statistically related, but form of ownership seems to matter. Firm size is also statistically correlated (positively) with profitability, but restructuring through changes in net employment growth appears not to be. It seems Russian restructuring needs to become more efficient.Labor Management and Relations,Labor Policies,Environmental Economics&Policies,Banks&Banking Reform,Municipal Financial Management,Labor Standards,Environmental Economics&Policies,Labor Management and Relations,Banks&Banking Reform,Municipal Financial Management

Spatial Correlation Robust Inference with Errors in Location or Distance

This paper presents results from a Monte Carlo study concerning inference with spatially dependent data. We investigate the impact of location/distance measurement errors upon the accuracy of parametric and nonparametric estimators of asymptotic variances. Nonparametric estimators are quite robust to such errors, method of moments estimators perform surprisingly well, and MLE estimators are very poor. We also present and evaluate a specification test based on a parametric bootstrap that has good power properties for the types of measurement error we consider.

Seeds of corruption - Do market institutions matter?

Ten years into the transition, corruption is so pervasive that it could jeopardize the best-intentioned reform efforts. The authors present an analytical framework for examining the role market institutions play in rent-seeking and illicit behavior. Using recently available data on the incidence of corruption, and on institutional development, they provide preliminary evidence on the link between the development of market institutions, and incentives for corruption. Virtually all of the indicators they examine appear to be important, but three are statistically significant: 1) the intensity of barriers to the entry of new business. 2) The effectiveness of the legal system. 3) The efficacy and competitiveness of services provided by infrastructure monopolies. The main lesson emerging from their analysis: a well established system of market institutions - clear and transparent rules, fully functioning checks and balances (including strong enforcement mechanisms), and a robust competitive environment - reduces opportunities for rent-seeking and hence incentives for corruption. Both the design, and effective implementation of such measures are important if a market system is to be effective. It is not enough, for example, to enact first-rate laws if they are not enforced. The local political economy greatly affects whether a given policy reform will curtail corruption. Especially important are the following factors in the political economy: a) the credibility of the government's commitment to carrying out announced reforms. B) The degree to which government officials are captured by the entities they regulate or oversee. C) the stability of the government itself. D) The political power of entrenched vested interests. Economists in the field of industrial organization, antitrust, and regulation have long recognized these factors as potent determinants of opportunistic behavior, corruption, and"capture"of government officials. Only now are they becoming conventional wisdom among specialists in economies in transition.Decentralization,International Terrorism&Counterterrorism,Economic Theory&Research,Environmental Economics&Policies,Legal Products,Governance Indicators,Legal Products,National Governance,Economic Theory&Research,Environmental Economics&Policies

Static polarizability of molecular materials: environmental and vibrational contributions

Modeling the dielectric behavior of molecular materials made up of large pi-conjugated molecules is an interesting and complex task. Here we address linear polarizabilities, and the related dielectric constant, of molecular crystals and aggregates made up of closed-shell pi-conjugated molecules with either a non-polar or largely polar ground-state, and also examine the behavior of mixed-valence (or charge-transfer) organic salts. We recognize important collective phenomena due to supramolecular interactions in materials with large molecular polarizabilities, and underline large vibrational contributions to the polarizability in materials with largely delocalized electrons.Comment: 18 pages, including 9 figure

Loss separation for dynamic hysteresis in magnetic thin films

We develop a theory for dynamic hysteresis in ferromagnetic thin films, on the basis of the phenomenological principle of loss separation. We observe that, remarkably, the theory of loss separation, originally derived for bulk metallic materials, is applicable to disordered magnetic systems under fairly general conditions regardless of the particular damping mechanism. We confirm our theory both by numerical simulations of a driven random--field Ising model, and by re--examining several experimental data reported in the literature on dynamic hysteresis in thin films. All the experiments examined and the simulations find a natural interpretation in terms of loss separation. The power losses dependence on the driving field rate predicted by our theory fits satisfactorily all the data in the entire frequency range, thus reconciling the apparent lack of universality observed in different materials.Comment: 4 pages, 6 figure

The Cagliari Airport impact on Sardinia tourism: a Logit-based analysis

In the field of air transportation management, traditionally, airlines have been the main actors in the process for deciding which new flights open in a given airport, while airports acted only as the managers of the operations. The changes in the market due to the introduction of low cost companies, with consequent reduction of the airports' fares, as well as the increment of the density of regional airports in several European countries are modifying the mutual roles of airlines and airports. The final decision on new flight to be opened, in fact, is nowadays the result of a negotiation between airlines and airports. The airports must prove the sustainability on the new routes and forecast the economic impact on their catchment area. This paper contributes to advance the current state-of-the-art along two axes. From the pure transportation literature point of view, we introduce a Logit model able to predict the passengers flow in an airport when the management introduces a change in the flight schedule. The model is also able to predict the impact of this change on the airports in the surrounding areas. The second contribution is a case study on the tourist market of the Sardinia region, where we show how to use the results of the model to deduce the economic impact of the decisions of the management of the Cagliari airport on its catchment area in terms of tourists and economic growt

Asymmetric switch costs in numeral naming and number word reading: Implications for models of bilingual language production

One approach used to gain insight into the processes underlying bilingual language comprehension and production examines the costs that arise from switching languages. For unbalanced bilinguals, asymmetric switch costs are reported in speech production, where the switch cost for Ll is larger than the switch cost for L2, whereas, symmetric switch costs are reported in language comprehension tasks, where the cost of switching is the same for L1 and L2. Presently, it is unclear why asymmetric switch costs are observed in speech production, but not in language comprehension. Three experiments are reported that simultaneously examine methodological explanations of task related differences in the switch cost asymmetry and the predictions of three accounts of the switch cost asymmetry in speech production. The results of these experiments suggest that (1) the type of language task (comprehension vs. production) determines whether an asymmetric switch cost is observed and (2) at least some of the switch cost asymmetry arises within the language system

Uniformly bounded representations and completely bounded multipliers of SL(2,R)

We estimate the norms of many matrix coefficients of irreducible uniformly bounded representations of SL(2, R) as completely bounded multipliers of the Fourier algebra. Our results suggest that the known inequality relating the uniformly bounded norm of a representation and the completely bounded norm of its coefficients may not be optimal