4,980 research outputs found
Brazilian Companies and the Grade of Investment
This study is featured in the context of applied typology, of descriptive goal with bibliographic outlining, in the extent of the issue it is features as quantitative, comprising the population of 70 Brazilian corporations recognized by the International certifying agents Standard & Poor’s, Moody’s and Fitch Ratings, which held the corporate investment grade in the year of 2012. Regarding the goal, the scope of this study was the development of an economic and financial indicator aiming to delimit the investment grade that companies present in their corporate structures, through a set of economic and financial indexes linked to liquidity, profitability, debt, and yield, from economic and financial demonstrations of the corporations studied.. The conclusions of the study were based in the results presented by the evolution of the statistical treatment, which were shown to be consistent for the model developed. The reliability of the model of corporate investment grade from the factorial analysis was testified by the Cronbach’s Alpha coefficient that presented value of 0.768, therefore indicating satisfactory consistence to the study
The American Religious Landscape and the 2004 Presidential Vote: Increased Polarization
Presents findings from a post-election survey conducted in November and December 2004. Explores the polarization between different religions, as well as within the major religious traditions
A dynamical dark energy model with a given luminosity distance
It is assumed that the current cosmic acceleration is driven by a scalar
field, the Lagrangian of which is a function of the kinetic term only, and that
the luminosity distance is a given function of the red-shift. Upon comparison
with Baryon Acoustic Oscillations (BAOs) and Cosmic Microwave Background (CMB)
data the parameters of the models are determined, and then the time evolution
of the scalar field is determined by the dynamics using the cosmological
equations. We find that the solution is very different than the corresponding
solution when the non-relativistic matter is ignored, and that the universe
enters the acceleration era at larger red-shift compared to the standard
model.Comment: 4 pages, 3 figures, accepted for publication in GER
Self Similar Solutions of the Evolution Equation of a Scalar Field in an Expanding Geometry
We consider the functional Schrodinger equation for a self interacting scalar
field in an expanding geometry. By performing a time dependent scale
transformation on the argument of the field we derive a functional Schrodinger
equation whose hamiltonian is time independent but involves a time-odd term
associated to a constraint on the expansion current. We study the mean field
approximation to this equation and generalize in this case, for interacting
fields, the solutions worked out by Bunch and Davies for free fields.Comment: 8 pages, Latex, IPNO/TH 94-3
The Functional Derivation of Master Equations
Master equations describe the quantum dynamics of open systems interacting
with an environment. They play an increasingly important role in understanding
the emergence of semiclassical behavior and the generation of entropy, both
being related to quantum decoherence. Presently we derive the exact master
equation for a homogeneous scalar Higgs or inflaton like field coupled to an
environment field represented by an infinite set of harmonic oscillators. Our
aim is to demonstrate a derivation directly from the path integral
representation of the density matrix propagator. Applications and
generalizations of this result are discussed.Comment: 10 pages; LaTex. - Contribution to the workshop Hadron Physics VI,
March 1998, Florianopolis (Brazil); proceedings, E. Ferreira et al., eds.
(World Scientific). Replaced by slightly modified published versio
Spike-timing dependent plasticity facilitates excitatory/inhibitory disbalances in early phases of tinnitus manifestation
© 2012 Metzner et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedThe majority of tinnitus cases are related to cochlear dysfunction, leading to altered peripheral input to the central auditory system. These alterations are believed to diminish the difference in activation during on- and off-conditions of sound. As a compensatory means the affected region of primary auditory cortex tries to maximize the difference between basic level activity and sound-induced activity by changing the excitatory /inhibitory balance. In a previous model comprising ~3000 multi-compartment Hodgkin-Huxley-type neurons, we have shown that solely an increase of excitatory influences may be sufficient to achieve these maximization. This previous Hodgkin-Huxley-type model did not take into account synaptic plasticity, howeverPeer reviewedFinal Published versio
Post-Newtonian expansion for Gauss-Bonnet Gravity
The Parametrized Post-Newtonian expansion of gravitational theories with a
scalar field coupled to the Gauss-Bonnet invariant is performed and
confrontation of such theories with Solar system experiments is discussed.Comment: 4 pages; typos corrected, published versio
On Spin-driven inflation from fields in General Relativity and COBE data
Obukhov spin-driven inflation in General Relativity is extended to include
inflaton fields.A de Sitter phase solution is obtained and new slow-rolling
conditions for the spin potential are obtained.The spin potential reduces to
Obukhov result at the present epoch of the Universe where the spin density is
low with comparison to the Early Universe spin densities.A relation betwenn the
spin density energy and the temperature fluctuation can be obtained which allow
us to determine the spin density energy in terms of the COBE data for
temperature fluctuations.Comment: Latex file 8K
Double Field Inflation
We present an inflationary universe model which utilizes two coupled real
scalar fields. The inflation field experiences a first order phase
transition and its potential dominates the energy density of the Universe
during the inflationary epoch. This field is initially trapped in its
metastable minimum and must tunnel through a potential barrier to reach the
true vacuum. The second auxiliary field couples to the inflaton field
and serves as a catalyst to provide an abrupt end to the inflationary epoch;
i.e., the field produces a time-dependent nucleation rate for bubbles of
true vacuum. In this model, we find that bubbles of true vacuum can
indeed percolate and we argue that thermalization of the interiors can more
easily take place. The required degree of flatness (i.e., the fine tuning) in
the potential of the field is comparable to that of other models which
invoke slowly rolling fields. Pseudo Nambu-Goldstone bosons may naturally
provide the flat potential for the rolling field.Comment: 18 pages, 2 figures, This early paper is being placed on the archive
to make it more easily accessible in light of recent interest in reviving
tunneling inflationary models and as its results are used in an accompanying
submissio
Variational Approach to Gaussian Approximate Coherent States: Quantum Mechanics and Minisuperspace Field Theory
This paper has a dual purpose. One aim is to study the evolution of coherent
states in ordinary quantum mechanics. This is done by means of a Hamiltonian
approach to the evolution of the parameters that define the state. The
stability of the solutions is studied. The second aim is to apply these
techniques to the study of the stability of minisuperspace solutions in field
theory. For a theory we show, both by means of perturbation
theory and rigorously by means of theorems of the K.A.M. type, that the
homogeneous minisuperspace sector is indeed stable for positive values of the
parameters that define the field theory.Comment: 26 pages, Plain TeX, no figure
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