1,352 research outputs found
Charm meson scattering cross sections by pion and rho meson
Using the local flavor SU(4) gauge invariance in the limit of vanishing
vector meson masses, we extend our previous study of charm meson scattering
cross sections by pion and rho meson, which is based only on the
pseudoscalar-pseudoscalar-vector meson couplings, to include also contributions
from the couplings among three vector mesons and among four particles. We find
that diagrams with light meson exchanges usually dominate the cross sections.
For the processes considered previously, the additional interactions lead only
to diagrams involving charm meson exchanges and contact interactions, and the
cross sections for these processes are thus not much affected. Nevertheless,
these additional interactions introduce new processes with light meson
exchanges and increase significantly the total scattering cross sections of
charm mesons by pion and rho meson.Comment: 14 pages, revtex, 6 figures, added a figure on the effects of
on-shell divergence, final version to appear in Nucl. Phys.
Low-mass dileptons and dropping rho meson mass
Using the transport model, we have studied dilepton production from heavy-ion
collisions at Bevalac energies. It is found that the enhanced production of
low-mass dileptons observed in the experiment by the DLS collaboration cannot
be explained by the dropping of hadron masses, in particular the -meson
mass, in dense matter.Comment: 9 pages, LaTeX, including 1 postscript figure, to appear in Phys.
Lett.
Competencies: requirements and acquisition
Higher education is given the key task to prepare the highly talented among the young to fulfil highly qualified roles in the labour market. Successful labour market performance of graduates is generally associated with the acquisition of the correct competencies. Education as an individual investment in human capital is a viewpoint dating back to the 17th century and the writings of Sir William Petty (1662), and includes later work by Adam Smith (1776). The idea was formalized and brought into mainstream economics by Schultz (1961), Becker (1964) and Mincer (1970, 1974). The strong supply-side orientation of the human capital theory’s determination of labour productivity has also raised serious doubts. One of the first major competitors of the human capital theory was the job competition model (Thurow, 1975), in its most extreme form explaining productivity entirely by occupational characteristics. Both the human capital theory and the job competition model in their original versions seem to be too restricted to one side of the labour market. More recently, therefore, approaches that allow explicitly for an interaction between supply-side and demand-side characteristics (‘assignment models’) have been placed centrally in analyses of education-to-work stages. For a good overview of different assignment models and their distinctive features with respect to matching models, such as proposed by Mortensen (1986), or search theories (e.g. Jovanovic, 1979), see Dupuy (2004)
Gravitational dipole radiations from binary systems
We investigate the possibility of generating sizeable dipole radiations in
relativistic theories of gravity. Optimal parameters to observe their effects
through the orbital period decay of binary star systems are discussed.
Constraints on gravitational couplings beyond general relativity are derived.Comment: One comment added, accepted for publication in Phys. Rev.
Avalanche dynamics, surface roughening and self-organized criticality - experiments on a 3 dimensional pile of rice
We present a two-dimensional system which exhibits features of self-organized
criticality. The avalanches which occur on the surface of a pile of rice are
found to exhibit finite size scaling in their probability distribution. The
critical exponents are = 1.21(2) for the avalanche size distribution and
= 1.99(2) for the cut-off size. Furthermore the geometry of the avalanches
is studied leading to a fractal dimension of the active sites of =
1.58(2). Using a set of scaling relations, we can calculate the roughness
exponent = 0.41(3) and the dynamic exponent = 1.56(8). This result is compared with that obtained from a power
spectrum analysis of the surface roughness, which yields = 0.42(3) and
= 1.5(1) in excellent agreement with those obtained from the scaling
relations.Comment: 7 pages, 8 figures, accepted for publication in PR
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