Studying the impact of the nucleon size in relativistic heavy-ion collisions

The hydrodynamic stage of relativistic heavy-ion collisions simulations requires an energy density profile of the system as an initial condition. In the process of converting the two colliding nuclei into such an energy distribution, some specification about the $\textit{size}$ of their constituent nucleons inevitably has to be made. Nucleons are commonly modeled as bidimensional Gaussians, and the Gaussian width (the nucleon-width) is a free parameter of the simulation. A best-fit value of the nucleon-width can be inferred by Bayesian Analyses, where the model is confronted with experimental data. Some of the most recent analyses have obtained surprisingly large values for the nucleon width parameter, exceeding in over 50 % the current value for the proton charged radius. This motivates the development of a better understanding of the role played by this parameter inside the simulation. In this work, we perform simulations of Pb-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 2.76 TeV using a state-of-the-art hybrid simulation chain, using three different values of the nucleon width inside the initial condition generator T$_{\text{R}}$ENTo, and systematically investigate its effects on the initial condition characteristics and observables. The nucleon-width strongly affects the eccentricity harmonics and the gradients in the initial condition. The $\langle p_{T} \rangle$ of particles in the simulation using $w$ = 0.5 fm is much larger than experimental data. We associate this to the combination of stronger gradients in the initial condition and the coupling of a conformal pre-equilibrium dynamics to the hydrodynamic simulation. Our findings suggest that the large values of the nucleon width returned by recent Bayesian Analyses were necessary to lower the mean transverse momentum, by damping the gradients in the initial condition.Comment: 75 pages, 40 figure

An analysis of quit and dismissal determinants between 1988 and 1999 using the bivariate probit model

Excessive labor turnover may be considered, to a great extent, an undesirable feature ofa given economy. This follows from considerations such as underinvestment in humancapital by firms. Understanding the determinants and the evolution of turnover in aparticular labor market is therefore of paramount importance, including policy considerations.The present paper proposes an econometric analysis of turnover in the Brazilianlabor market, based on a partial observability bivariate probit model. This model considersthe interdependence of decisions taken by workers and firms, helping to elucidate thecauses that lead each of them to end an employment relationship. The Employment andUnemployment Survey (PED) conducted by the State System of Data Analysis (SEADE)and by the Inter-Union Department of Statistics and Socioeconomic Studies (DIEESE)provides data at the individual worker level, allowing for the estimation of the joint probabilitiesof decisions to quit or stay on the job on the worker’s side, and to maintain orfire the employee on the firm’s side, during a given time period. The estimated parametersrelate these estimated probabilities to the characteristics of workers, job contracts,and to the potential macroeconomic determinants in different time periods. The resultsconfirm the theoretical prediction that the probability of termination of an employmentrelationship tends to be smaller as the worker acquires specific skills. The results alsoshow that the establishment of a formal employment relationship reduces the probabilityof a quit decision by the worker, and also the firm’s firing decision in non-industrialsectors. With regard to the evolution of quit probability over time, the results show thatan increase in the unemployment rate inhibits quitting, although this tends to wane asthe unemployment rate rises.

The applied perspective for seasonal cointegration testing

While the literature on cointegration deals exclusively with the case of cointegration at the long-run or zero frequency between series in a vector of economic variables, it may happen that unit-roots are also present at the seasonal frequencies, and hence the concept of cointegration can be extended to the case of seasonal cointegration. In this paper we survey the available procedures for testing and estimating cointegration relationships at the seasonal frequencies, as well as at the zero frequency when seasonal unit-roots are present. A strong motivation for this is the lack of treatment of seasonal cointegration, even in the most recent books on cointegration.Enquanto a literatura sobre cointegração lida exclusivamente com o caso de cointegração no longo prazo, ou na frequência zero, entre séries em um vetor de variáveis econômicas, pode ser que raízes unitárias estejam também presentes nas frequências sazonais, de forma que o conceito de cointegração pode ser extendido para o caso de cointegração sazonal. Neste artigo, fazemos uma resenha dos procedimentos disponíveis para testar e estimar as relações de cointegração nas frequências sazonais, bem como na frequência zero, quando raízes unitárias sazonais estão presentes. Uma motivação importante para este trabalho é a falta de um tratamento sobre cointegração sazonal, mesmo nos livros-texto mais recentes sobre cointegração

Can the distributional impacts of macroeconomic shocks be predicted? A comparison of the performance of macro-micro models with historical data for Brazil

What was the impact of Brazil's 1998-99 currency crisis-which resulted in a change of exchange rate regime and a large real devaluation-on the occupational structure of the labor force and the distribution of incomes? Would it have been possible to predict such effects ahead of the crisis? The authors present an integrated macro-micro model of the Brazilian economy in 1998. The model consists of an applied general equilibrium macroeconometric component, connected through a set of linkage aggregate variables to a microeconomic model of household incomes. The authors use this framework to predict the employment and distributional consequences of the 1999 Brazilian currency crisis, based on 1998 household survey data. They then test the predictive performance of the model by comparing its simulated results with the actual household survey data observed in 1999. In addition to the fully integrated macro-micro model, the authors also test the performances of the microeconometric model on its own, and of a"representative household groups"approach. They find that the integrated macro-micro econometric model, while still inaccurate on many dimensions, can actually predict the broad pattern of the incidence of changes in household incomes across the distribution reasonably well, and much better than the alternative approaches. The authors conclude that further experimentation with these tools might be of considerable potential usefulness to policymakers.Labor Policies,Payment Systems&Infrastructure,Economic Theory&Research,Banks&Banking Reform,Environmental Economics&Policies,Economic Theory&Research,Environmental Economics&Policies,Macroeconomic Management,Inequality,Economic Stabilization

Non-Gaussian transverse momentum fluctuations from impact parameter fluctuations

The transverse momentum per particle, $[p_t]$, fluctuates event by event in ultrarelativistic nucleus-nucleus collisions, for a given multiplicity. These fluctuations are small and approximately Gaussian, but a non-zero skewness has been predicted on the basis of hydrodynamic calculations, and seen experimentally. We argue that the mechanism driving the skewness is that, if the system thermalizes, the mean transverse momentum increases with impact parameter for a fixed collision multiplicity. We postulate that fluctuations are Gaussian at fixed impact parameter, and that non-Gaussianities solely result from impact parameter fluctuations. Using recent data on the variance of $[p_t]$ fluctuations, we make quantitative predictions for their skewness and kurtosis as a function of the collision multiplicity. We predict in particular a spectacular increase of the skewness below the knee of the multiplicity distribution, followed by a fast decrease.Comment: 8 pages, 5 figures. v2: Minor revisio

How much to trim? A methodology for calculating core inflation, with an application for Brazil

The concept of core inflation has been central to the discussions concerning macroeconomic policy management. In spite of this fact, no single measure of this concept has achieved consensus so far. Here, we propose the application of a statistical methodology based on trimmed means, where the amount of trim is based on a benchmark provided by a common stochastic components model, which we believe captures the essence of the core inflation concept. We apply this measure to the IPC-FIPE and IPCA-IBGE, two of the leading consumer price indexes in Brazil, and comment on the results.O conceito de núcleo da inflação tem ocupado um papel central nas discussões envolvendo políticas macroeconômicas. A despeito disso, nenhuma medida consensual deste conceito existe até agora. Neste artigo, propomos a aplicação da metodologia estatística baseada em médias aparadas, onde o tamanho da apara é baseado em uma referência proporcionada por modelos de componentes estocásticos comuns, os quais acreditamos captar a essência do conceito de nucleo da inflação. Estas medidas são aplicadas ao IPC-FIPE e ao IPCA-IBGE, dois dos principais índices de preços ao consumidor no Brasil, e comentamos os resultados

Towards an economic theory of strikes: Further evidence from Brazilian data

We analyse the history of the labor movement in Brazil since the beginning of its industrialization, with particular emphasis on the legislation governing labor disputes. A data set on strike activity for that country during the period between 1983 and 1993 is first analysed at the descriptive level, and then used to produce results based on statistical methods of frequency and duration analysis. The obtained results of frequency and duration of strikes, including their relationships with some macroeconomic variables, are compared with ones from similar studies using data from the US and Canada. The comparison shows that there seems to be a common pattern of results in these countries. An explanation for the observed features of these patterns is then sought in the context of game-theoretic models of bargaining, and suggestions for future research in the area are given.U of I OnlyETDs are only available to UIUC Users without author permissio