Stability measures in metastable states with Gaussian colored noise

We present a study of the escape time from a metastable state of an overdamped Brownian particle, in the presence of colored noise generated by Ornstein-Uhlenbeck process. We analyze the role of the correlation time on the enhancement of the mean first passage time through a potential barrier and on the behavior of the mean growth rate coefficient as a function of the noise intensity. We observe the noise enhanced stability effect for all the initial unstable states used, and for all values of the correlation time $\tau_c$ investigated. We can distinguish two dynamical regimes characterized by weak and strong correlated noise respectively, depending on the value of $\tau_c$ with respect to the relaxation time of the system.Comment: 6 pages, 7 figure

The Mayer series of the Lennard-Jones gas: improved bounds for the convergence radius

We provide a lower bound for the convergence radius of the Mayer series of the Lennard-Jones gas which strongly improves on the classical bound obtained by Penrose and Ruelle 1963. To obtain this result we use an alternative estimate recently proposed by Morais et al. (J. Stat. Phys. 2014) for a restricted class of stable and tempered pair potentials (namely those which can be written as the sum of a non-negative potential plus an absolutely integrable and stable potential) combined with a method developed by Locatelli and Schoen (J. Glob. Optim. 2002) for establishing a lower bound for the minimal interatomic distance between particles interacting via a Morse potential in a cluster of minimum-energy configurations

Human capital differentials across municipalities and states in Brazil

In this paper, we investigate the distribution of more educated and skilled people in Brazilian municipalities and states. Previous evidence shows a high concentration of college educated and high skilled workers in some areas of the country. We investigate whether the increase in the number of high skill workers is faster in municipalities with high initial levels of human capital than in municipalities with lower initial levels. We develop a theoretical model to explain the convergence/divergence of regional skill levels In Brazil. We estimate OLS models based on the theoretical model to explain empirically wage differentials in Brazil. Last, we compute standard segregation and isolation measures to show the trends in the distribution of skilled workers across states and cities in Brazil. We find that educated and qualified workers are concentrated in some areas of the country and recent decades show a higher concentration of them across states and cities.human capital, segregation, regional differences, Brazil

INCORPORATING UNCERTAINTY IN THE ANALYSIS OF OPTIMAL BEEF-FORAGE PRODUCTION SYSTEMS

A risk programming model was developed to evaluate the tradeoffs between risk and expected returns in beef-forage production systems. The specification represents nutrient and intake considerations when allocating forage among cattle enterprises; it also incorporates the various sources of risk facing livestock producers. Efficient ranch organizations were derived for a representative eastern Oklahoma ranch using MOTAD and Target-MOTAD formulations. Diversification of forage enterprises, introduction of cow-calf enterprises, and retained ownership of weaned calves were identified as important responses to reductions in acceptable levels of risk. Results also indicated efficient ranch plans to be sensitive to the risk criteria and producer's willingness to accept risk.Livestock Production/Industries, Risk and Uncertainty,

Breathers in inhomogeneous nonlinear lattices: an analysis via centre manifold reduction

We consider an infinite chain of particles linearly coupled to their nearest neighbours and subject to an anharmonic local potential. The chain is assumed weakly inhomogeneous. We look for small amplitude discrete breathers. The problem is reformulated as a nonautonomous recurrence in a space of time-periodic functions, where the dynamics is considered along the discrete spatial coordinate. We show that small amplitude oscillations are determined by finite-dimensional nonautonomous mappings, whose dimension depends on the solutions frequency. We consider the case of two-dimensional reduced mappings, which occurs for frequencies close to the edges of the phonon band. For an homogeneous chain, the reduced map is autonomous and reversible, and bifurcations of reversible homoclinics or heteroclinic solutions are found for appropriate parameter values. These orbits correspond respectively to discrete breathers, or dark breathers superposed on a spatially extended standing wave. Breather existence is shown in some cases for any value of the coupling constant, which generalizes an existence result obtained by MacKay and Aubry at small coupling. For an inhomogeneous chain the study of the nonautonomous reduced map is in general far more involved. For the principal part of the reduced recurrence, using the assumption of weak inhomogeneity, we show that homoclinics to 0 exist when the image of the unstable manifold under a linear transformation intersects the stable manifold. This provides a geometrical understanding of tangent bifurcations of discrete breathers. The case of a mass impurity is studied in detail, and our geometrical analysis is successfully compared with direct numerical simulations

The Rise of Accelerated Seasoned Equity Underwritings

Seasoned equity offerings (SEOs) executed through accelerated underwritings have increased global market share recently, raising over $850 billion since 1998, and now account for over half (two-thirds) of the value of U.S. (European) SEOs. We examine 31,242 global SEOs, executed during 1991-2004, which raise over$2.9 trillion for firms and selling shareholders. Compared to fully marketed deals, accelerated offerings occur more rapidly, raise more money, and require fewer underwriters. Importantly, accelerated deals reduce total issuance cost by about 250 basis points. Accelerated deals sell equal fractions of primary and secondary shares, whereas in traditional SEOs primary shares dominate. Announcement period returns are comparable for traditional and accelerated offerings, while secondary and mixed offerings trigger more negative market responses than do primary offerings. We conclude that this rapid, worldwide shift towards accelerated underwriting creates a spot market for SEOs, and represents the long-predicted shift towards an auction model for seasoned equity sales.Equity Offerings, Underwriting, Investment Banking