13,169 research outputs found
Discrepancies between empirical and theoretical models of the flaring solar chromosphere and their possible resolution
Models of the solar chromosphere during flaring deduced theoretically or empirically are compared. Marked discrepancies are noted and various reasons are offered to explain their existence. A means is presented for testing theoretical heating models (electron heating) by analyzing the net energy loss rates in (observed) empirical atmospheres and inverting the flare energy equation to deduce the parameters of the supposed heating mechanism
On fermion masses and mixing in a model with symmetry
In a recently proposed multi-Higgs extension of the standard model in which
discrete symmetries, and are imposed we show that, after
accommodating the fermion masses and the mixing matrices in the charged
currents, the mixing matrices in the neutral currents induced by neutral
scalars are numerically obtained. However, the flavor changing neutral currents
are under control mainly by mixing and/or mass suppressions in the neutral
scalar sector.Comment: Version accepted for publication in International Journal of Modern
Physics A. In this version we added a discussion on the charged lepton and
neutrino masses. The title has been changed. Other minor changes do not
modify the conclusion
Sustainable management methods: performance assessment in large companies
The general objective of this study is to contribute to the understanding of the performance evaluation methods used by large companies. As specific objectives we have the following: to identify the methods used and the importance attributed to them; to analyse their implementation process and the level of success given to it. The data collection method used was a survey to the financial managers of the largest companies in Portugal, which resulted in thirty-five valid responses. The main contributions of this study were the associations found between the following variables: the method used and the level of importance assigned to it; the person in charge of implementing the method and training provided to employees; the method used and the degree of success attributed to its implementation; the degree of resistance to change and the degree of success in implementing the performance evaluation method.info:eu-repo/semantics/acceptedVersio
Fractional Hamiltonian analysis of higher order derivatives systems
The fractional Hamiltonian analysis of 1+1 dimensional field theory is
investigated and the fractional Ostrogradski's formulation is obtained. The
fractional path integral of both simple harmonic oscillator with an
acceleration-squares part and a damped oscillator are analyzed. The classical
results are obtained when fractional derivatives are replaced with the integer
order derivatives.Comment: 13 page
Evidence of Low-Temperature Superparamagnetism in Mn_{4}$ Nanoparticle Ensembles
Please refer to the abstract within the main body of the paper
Lagrangian formulation of classical fields within Riemann-Liouville fractional derivatives
The classical fields with fractional derivatives are investigated by using
the fractional Lagrangian formulation.The fractional Euler-Lagrange equations
were obtained and two examples were studied.Comment: 9 page
Type O pure radiation metrics with a cosmological constant
In this paper we complete the integration of the conformally flat pure
radiation spacetimes with a non-zero cosmological constant , and , by considering the case . This is a
further demonstration of the power and suitability of the generalised invariant
formalism (GIF) for spacetimes where only one null direction is picked out by
the Riemann tensor. For these spacetimes, the GIF picks out a second null
direction, (from the second derivative of the Riemann tensor) and once this
spinor has been identified the calculations are transferred to the simpler GHP
formalism, where the tetrad and metric are determined. The whole class of
conformally flat pure radiation spacetimes with a non-zero cosmological
constant (those found in this paper, together with those found earlier for the
case ) have a rich variety of subclasses with zero,
one, two, three, four or five Killing vectors
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