Self-organizing social hierarchies on scale-free networks

In this work we extend the model of Bonabeau et al. in the case of scale-free networks. A sharp transition is observed from an egalitarian to an hierarchical society, with a very low population density threshold. The exact threshold value also depends on the network size. We find that in an hierarchical society the number of individuals with strong winning attitude is much lower than the number of the community members that have a low winning probability

The real effects of financial stress in the Euro zone

Using two identification strategies based on a Bayesian Structural VAR and a Sign-Restriction VAR, we examine the real effects of financial stress in the Eurozone. In particular, we assess the macroeconomic impact of: (i) a monetary policy shock; and (ii ) a financial stress shock. We find that a monetary policy contraction strongly deteriorates financial stress conditions. In addition, unexpected variation in the Financial Stress Index (FSI) plays an important role in explaining output fluctuations, and also demands an aggressive response by the monetary authority to stabilise output indicating a preference shift from targeting inflation as it is currently happening in major economies. Therefore, our paper reveals the importance of adopting a vigilant posture towards financial stress conditions, as well as the urgency of macro-prudential risk management.monetary policy, financial stress, Bayesian Structural VAR, Sign-Restrictions, Euro-zone.

Monetary Policy Rules in the BRICS: How Important is Nonlinearity?

Given limited research on monetary policy rules in emerging markets, this paper estimates monetary policy rules for five key emerging market economies: Brazil, Russia, India, China and South Africa (BRICS) analysing whether the monetary authority reacts to changes in financial markets, in monetary conditions, in the foreign exchange sector and in the commodity price. To get a deeper understanding of the central bank’s behaviour, we assess the importance of nonlinearity using a smooth transition (STAR) model. Using quarterly data, we find strong evidence that the monetary policy followed by the Central Banks in the BRICS varies from one country to another and that it exhibits nonlinearity. In particular, considerations about economic growth (in the cases of Brazil and Russia), inflation (for India and China) and stability of financial markets (in South Africa) seem to be the major drivers of such nonlinear monetary policy behaviour. Moreover, the findings suggest that the monetary authorities pursue, with the exception of India, a target range for the threshold variable rather than a specific point target. In fact, the exponential smooth transition regression (ESTR) model seems to be the best description of the monetary policy rule in these countries.monetary policy, emerging markets, smooth transition.

Fiscal Policy in the BRICs

This paper assesses the macroeconomic impact of fiscal policy shocks for four key emerging market economies - Brazil, Russia, India and China (BRICs) – using a Bayesian Structural Vector Auto-Regressive (BSVAR) approach, a Sign-Restrictions Vector Auto-Regressive framework and a Panel Vector Auto-Regressive (PVAR) model. To get a deeper understanding of the government’s behaviour, we also estimate fiscal policy rules using a Fully Simultaneous System of Equations and analyze the importance of nonlinearity using a smooth transition (STAR) model. Drawing on quarterly frequency data, we find that government spending shocks have strong Keynesian effects for this group of countries while, in the case of government revenue shocks, a tax hike is harmful for output. This suggests that there is no evidence in favour of ‘expansionary fiscal contraction’ in the context of emerging economies where spending policies are largely pro-cyclical. Our findings also show that considerations about growth (in the case of China), exchange rate and inflation (for Brazil and Russia) and commodity prices (in India) drive the nonlinear response of fiscal policy to the dynamics of the economy. All in all, our results are consistent with the idea that fiscal policy can be a powerful stabilization tool and can provide an important short-term economic boost for emerging markets, in particular, in the context of severe downturns as in most recent financial turmoil.fiscal policy, emerging markets, fully simultaneous system of equations, sign-restrictions VAR, smooth transition regression model

Estimating and controlling the traffic Impact of a collaborative P2P system

Nowadays, P2P applications are commonly used in the Internet being an important paradigm for the development of distinct services. However, the dissemination of P2P applications also entails some important challenges that should be carefully addressed. In particular, some of the important coexistence problems existing between P2P applications and Internet Service Providers (ISPs) are mainly motivated by the inherent P2P dynamics which cause traffic to scatter across the network links in an unforeseeable way. In this context, this work proposes a collaborative framework of a Bit- Torrent like system. Using the proposed framework and based on the exchange of valuable information between the application and network levels, some novel techniques are proposed allowing to estimate and control the traffic impact that the P2P system will have on the links of the underlying network infrastructure. Both the framework and the presented techniques were tested resorting to simulation. The results clearly corroborate the viability and effectiveness of the formulated methods

Ohmic and step noise from a single trapping center hybridized with a Fermi sea

We show that single electron tunneling devices such as the Cooper-pair box or double quantum dot can be sensitive to the zero-point fluctuation of a single trapping center hybridized with a Fermi sea. If the trap energy level is close to the Fermi sea and has line-width \gamma > k_B T, its noise spectrum has an Ohmic Johnson-Nyquist form, whereas for \gamma < k_B T the noise has a Lorentzian form expected from the semiclassical limit. Trap levels above the Fermi level are shown to lead to steps in the noise spectrum that can be used to probe their energetics, allowing the identification of individual trapping centers coupled to the device.Comment: Revised version to appear in Phys. Rev. Let

Reshuffling spins with short range interactions: When sociophysics produces physical results

Galam reshuffling introduced in opinion dynamics models is investigated under the nearest neighbor Ising model on a square lattice using Monte Carlo simulations. While the corresponding Galam analytical critical temperature T_C \approx 3.09 [J/k_B] is recovered almost exactly, it is proved to be different from both values, not reshuffled (T_C=2/arcsinh(1) \approx 2.27 [J/k_B]) and mean-field (T_C=4 [J/k_B]). On this basis, gradual reshuffling is studied as function of 0 \leq p \leq 1 where p measures the probability of spin reshuffling after each Monte Carlo step. The variation of T_C as function of p is obtained and exhibits a non-linear behavior. The simplest Solomon network realization is noted to reproduce Galam p=1 result. Similarly to the critical temperature, critical exponents are found to differ from both, the classical Ising case and the mean-field values.Comment: 11 pages, 5 figures in 6 eps files, to appear in IJMP

AN ECONOMIC ANALYSIS OF THE RELATIONSHIP OF POVERTY AND INCOME INEQUALITY IN RURAL WEST VIRGINIA

Ordinary and two-stage least square regressions were used to examine the major determinants of poverty and income inequality with cross-sectional data of 38 rural counties of West Virginia. The empirical findings confirm the possibility of simultaneity between poverty and income inequality and poverty level is the main determinant of increased levels of income inequality. The proportions of population in welfare, population of age 65 or older, female-headed households, people unemployed, and the level of inequality contributed to increased poverty levels. The proportion of employment shares in finance, insurance and real estate, and per capita income contributed to reduced poverty levels. But, per capita income, the proportion of human capital stock, and the proportion of employment shares in manufacturing contributed to reduced income inequality.Food Security and Poverty,