Meron-cluster simulation of the quantum antiferromagnetic Heisenberg model in a magnetic field in one- and two-dimensions

Motivated by the numerical simulation of systems which display quantum phase transitions, we present a novel application of the meron-cluster algorithm to simulate the quantum antiferromagnetic Heisenberg model coupled to an external uniform magnetic field both in one and in two dimensions. In the infinite volume limit and at zero temperature we found numerical evidence that supports a quantum phase transition very close to the critical values $B_{c}=2$ and $B_{c}=4$ for the system in one and two dimensions, respectively. For the one dimensional system, we have compared the numerical data obtained with analytical predictions for the magnetization density as a function of the external field obtained by scaling-behaviour analysis and Bethe Ansatz techniques. Since there is no analytical solution for the two dimensional case, we have compared our results with the magnetization density obtained by scaling relations for small lattice sizes and with the approximated thermodynamical limit at zero temperature guessed by scaling relations. Moreover, we have compared the numerical data with other numerical simulations performed by using different algorithms in one and two dimensions, like the directed loop method. The numerical data obtained are in perfect agreement with all these previous results, which confirms that the meron-algorithm is reliable for quantum Monte Carlo simulations and applicable both in one and two dimensions. Finally, we have computed the integrated autocorrelation time to measure the efficiency of the meron algorithm in one dimension.Comment: 18 pages, 11 figure

Argentina's labor markets in an era of adjustment

The current economic crisis in Argentina is only partly the result of inappropriate domestic policies to cope with the recent external shocks. Years of inappropriate policies have damaged Argentina's economy. Even if no external shocks had occurred, the country would still have to change the structure of production. Argentina has had trouble sustaining a program of structural adjustment. Its experiences provide policymakers with some lessons in designing a sustainable program to achieve price stability and change the incentive system : a) macroeconomic and trade policies must be consistent; b) labor relations and labor market institutions must be changed including the decentralization of wage bargaining and the elimination of traditional wage policies and general government intervention; c) rigidities and restrictions on labor mobility must be eliminated, leading to less pervasive government intervention in the form of restrictive regulations and spending patterns; and d) public spending must be profoundly changed to reduce social costs during the transition period.Economic Stabilization,Banks&Banking Reform,Municipal Financial Management,Environmental Economics&Policies,Economic Theory&Research

Macroeconomic adjustment and the labor market in four Latin American countries

Implicit in standard macroeconomics of adjustment is the assumption of well-integrated labor markets that are responsive to relative prices. But segmentation of the labor market is usually said to be an important source of labor market rigidities. In particular, if segmentation involves different degrees of real wage rigidity among different groups in the labor force, nominal devaluation may be ineffective and inequitable in its impact. This paper uses a model of labor market segmentation in which regulations are necessary to distinguish between the formal and informal sectors. Using standard econometric techniques to estimate four simultaneous equations, the authors examine the effect of devaluation on relative wages in four countries. They found that formal wages are more responsive than informal wages to inflation and that devaluation of the exchange rate, by increasing the wage gap, is a source of sluggish labor mobility. In addition, they found that expanding wage differentials during adjustment imposes a greater burden on the poorest workers, making adjustment policies less politically sustainable. Finally, they found evidence to support the hypothesis that nominal devaluation would probably be ineffective with a segmented labor market.Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,Labor Markets,Health Economics&Finance

Adjustment and the labor market

How has the labor market responded to changes in macroeconomic conditions and related government policies? And to what extent has government intervention affected the microeconomic functioning of the labor market. Geographical immobility of workers does not seem to hinder adjustment. Labor is increasingly deployed in nontradables and import competing sectors, however, and problems of mobility between tradables and nontradables are reported. In addition, shortages of skilled manpower are reported. There is little evidence of wage resistence where wage indexation is not institutionalized. Traditional methods of wage support have become less important in the past two decades. Where effective minimum wage policies exist, they have the expected distortionary effects. Wage differences between the public and private sectors, particularly in sub-Saharan Africa, have continued to widen, and the efficiency of the public sector has declined as a result. Job security regulations may be an obstacle to structural adjustment programs insofar as they hinder the release of labor from contracting sectors.Environmental Economics&Policies,Banks&Banking Reform,Economic Theory&Research,Health Economics&Finance,Poverty Assessment

Wage responsiveness and labor market disequilibrium

The objectives of this paper are : (i) to empirically probe on the validity of the hypothesis that wages are relatively unresponsive to labor market disequlibrium; and (ii) to investigate whether the dramatically diverse rates of unemployment observed across certain Latin American countries obey fundamentally different wage dynamics or are the product of diversity in labor market distortions and other labor market policies. The indications found are that core unemployment may not affect market wages, whereas transient unemployment does. Policymaking should reflect the distinction.Environmental Economics&Policies,Youth and Governance,Economic Theory&Research,Labor Markets,Health Monitoring&Evaluation