8,132 research outputs found
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
investigated. We can distinguish two dynamical regimes characterized by weak
and strong correlated noise respectively, depending on the value of
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 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
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