3,225 research outputs found
LOCV calculations for polarized liquid with the spin-dependent correlation
We have used the lowest order constrained variational (LOCV) method to
calculate some ground state properties of polarized liquid at zero
temperature with the spin-dependent correlation function employing the
Lennard-Jones and Aziz pair potentials. We have seen that the total energy of
polarized liquid increases by increasing polarization. For all
polarizations, it is shown that the total energy in the spin-dependent case is
lower than the spin-independent case. We have seen that the difference between
the energies of spin-dependent and spin-independent cases decreases by
increasing polarization. We have shown that the main contribution of the
potential energy comes from the spin-triplet state.Comment: 14 pages, 5 figures. Int. J. Mod. Phys. B (2008) in pres
Next-to-leading order QCD calculations with parton showers II: soft singularities
Programs that calculate observables in quantum chromodynamics at
next-to-leading order typically generate events that consist of partons rather
than hadrons -- and just a few partons at that. These programs would be much
more useful if the few partons were turned into parton showers, which could be
given to one of the Monte Carlo event generators to produce hadron showers. In
a previous paper, we have seen how to generate parton showers related to the
final state collinear singularities of the perturbative calculation for the
example of e+ + e- --> 3 jets. This paper discusses the treatment of the soft
singularities.Comment: 26 pages with 5 figures. This version is close to the version to be
publishe
Epitaxial Growth Kinetics with Interacting Coherent Islands
The Stranski-Krastanov growth kinetics of undislocated (coherent)
3-dimensional islands is studied with a self-consistent mean field rate theory
that takes account of elastic interactions between the islands. The latter are
presumed to facilitate the detachment of atoms from the islands with a
consequent decrease in their average size. Semi-quantitative agreement with
experiment is found for the time evolution of the total island density and the
mean island size. When combined with scaling ideas, these results provide a
natural way to understand the often-observed initial increase and subsequent
decrease in the width of the coherent island size distribution.Comment: 4 pages, 4 figure
Some closure operations in Zariski-Riemann spaces of valuation domains: a survey
In this survey we present several results concerning various topologies that
were introduced in recent years on spaces of valuation domains
Incorporating next-to-leading order matrix elements for hadronic diboson production in showering event generators
A method for incorporating information from next-to-leading order QCD matrix
elements for hadronic diboson production into showering event generators is
presented. In the hard central region (high jet transverse momentum) where
perturbative QCD is reliable, events are sampled according to the first order
tree level matrix element. In the soft and collinear regions next-to-leading
order corrections are approximated by calculating the differential cross
section across the phase space accessible to the parton shower using the first
order (virtual graphs included) matrix element. The parton shower then provides
an all-orders exclusive description of parton emissions. Events generated in
this way provide a physical result across the entire jet transverse momentum
spectrum, have next-to-leading order normalization everywhere, and have
positive definite event weights. The method is generalizable without
modification to any color singlet production process.Comment: 13 pages, 9 figure
Simulations of spiral galaxies with an active potential: molecular cloud formation and gas dynamics
We describe simulations of the response of a gaseous disc to an active spiral
potential. The potential is derived from an N-body calculation and leads to a
multi-armed time-evolving pattern. The gas forms long spiral arms typical of
grand design galaxies, although the spiral pattern is asymmetric. The primary
difference from a grand-design spiral galaxy, which has a consistent 2/4-armed
pattern, is that instead of passing through the spiral arms, gas generally
falls into a developing potential minimum and is released only when the local
minimum dissolves. In this case, the densest gas is coincident with the spiral
potential, rather than offset as in the grand-design spirals. We would there
fore expect no offset between the spiral shock and star formation, and no
obvious co-rotation radius. Spurs which occur in grand-design spirals when
large clumps are sheared off leaving the spiral arms, are rare in the active,
time-evolving spiral reported here. Instead, large branches are formed from
spiral arms when the underlying spiral potential is dissolving due to the
N-body dynamics. We find that the molecular cloud mass spectrum for the active
potential is similar to that for clouds in grand design calculations, depending
primarily on the ambient pressure rather than the nature of the potential. The
largest molecular clouds occur when spiral arms collide, rather than by
agglomeration within a spiral arm.Comment: 11 pages, 7 figures, accepted for publication in MNRA
Polygenic threshold model with sex dimorphism in adolescent idiopathic scoliosis: The Carter effect
Background: Idiopathic clubfoot is approximately twice as common in males than in females. The reason for this discrepancy is unclear butmay represent an inherent difference in the susceptibility to thedeformity. If this difference is due to genetic factors it is predicted that in order to inherit clubfoot, females need to have a greater number of susceptibility genes than males. Females would also be more likely to transmit the disease to their children and have siblings with clubfoot. This phenomenon is known as the Carter effect, and the presence of such an effect supports a multifactorial threshold model of inheritance. Methods: Ninety-seven multiplex families with more than one individual with idiopathic clubfoot were studied. The study included1093 individuals: 291with clubfoot and802unaffected relatives. Ratesof transmissionby the thirty-seven affected fathers and twenty-six affected mothers were calculated, and the prevalence among siblings was determined in the nuclear families of affected persons
CP Violation in \tau ->\nu\pi K_S and D->\pi K_S: The Importance of K_S-K_L Interference
The -factories have measured CP asymmetries in the and
modes. The state is identified by its decay to two pions at
a time that is close to the lifetime. Within the Standard Model and many
of its extensions, the asymmetries in these modes come from CP violation in
mixing. We emphasize that the interference between the
amplitudes of intermediate and is as important as the pure
amplitude. Consequently, the measured asymmetries depend on the times over
which the relevant decay rates are integrated and on features of the
experiment.Comment: 4 pages, 4 figure
Dynamics of Metal Centers Monitored by Nuclear Inelastic Scattering
Nuclear inelastic scattering of synchrotron radiation has been used now since
10 years as a tool for vibrational spectroscopy. This method has turned out
especially useful in case of large molecules that contain a M\"ossbauer active
metal center. Recent applications to iron-sulfur proteins, to iron(II) spin
crossover complexes and to tin-DNA complexes are discussed. Special emphasis is
given to the combination of nuclear inelastic scattering and density functional
calculations
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