1,252 research outputs found
Minimal mass-size of a stable 3He cluster
The minimal number of 3He atoms required to form a bound cluster has been
estimated by means of a Diffusion Monte Carlo procedure within the fixed-node
approximation. Several importance sampling wave functions have been employed in
order to consider different shell-model configurations. The resulting upper
bound for the minimal number is 32 atoms.Comment: 2 pages, no figure
Factors affecting rind pitting in the mandarin hybrids "fortune" and "nova". The influence of exogenous growth regulators
The commercialization of the mandarin hybrids "Fortune" and "Nova" is hindered by the development of cold-induced pitting in the fruit rind which may develop either in the orchard or during storage and transport.
In the late cropping cultivar "Fortune", the pitting develops on tree during the winter months and affects mainly the exposed fruit from the north-west quadrant of the tree. The induction of symptoms under uniform conditions in the cold-room reveals differences in the susceptibility to chilling injury among the fruits and the fruit sides. The green fruit is not susceptible. Susceptibility develops as pigmentation progresses, and it is higher for the exposed than for the non-exposed (covered by the foliage) fruits. The application of GA3 at colour-break delays pigmentation and retards the development of susceptibility. The waxing of the fruit offers some protection to cold in the cold-room. However, the incidence of pitting is not related to the wax content of the fruit rind and the application of a wax coverage on tree had only a marginal protective effect.
No pitting is usually found on tree in the fruit of the early ripening "Nova" cultivar, which is usually harvested before the winter chilling. The pitting develops during cold storage (8-10 C), and is reduced by GA3 application at colour break, an effect related to the delay in rind pigmentation.info:eu-repo/semantics/publishedVersio
Excitation spectra of a 3He impurity on 4He clusters
The diffusion Monte Carlo technique is used to calculate and analyze the
excitation spectrum of a single 3He atom bound to a cluster with N 4He atoms,
with the aim of establishing the most adequate filling ordering of
single-fermion orbits to the mixed clusters with a large number of 3He atoms.
The resulting ordering looks like the rotational spectrum of a diatomic
molecule, being classified only by the angular momentum of the level, although
vibrational-like excitations appear at higher energies for sufficiently large
N
Translationally-invariant coupled-cluster method for finite systems
The translational invariant formulation of the coupled-cluster method is
presented here at the complete SUB(2) level for a system of nucleons treated as
bosons. The correlation amplitudes are solution of a non-linear coupled system
of equations. These equations have been solved for light and medium systems,
considering the central but still semi-realistic nucleon-nucleon S3
interaction.Comment: 16 pages, 2 Postscript figures, to be published in Nucl. Phys.
Excited states of 4He droplets
We study low-lying excited states of 4He clusters up to a cluster size of 40 atoms in a variational framework. The ansatz wave function combines two- and three-body correlations, coming from a translationally invariant configuration interaction description, and Jastrow-type short-range correlation. We have previously used this scheme to determine the ground-state energies of 4He and 3He clusters. Here we present an extension of this ansatz wave function having a good quantum angular momentum L. The variational procedure is applied independently to the cases with L = 0,2,4, and upper bounds for the corresponding energies are thus obtained. Moreover, centroid energies for L excitations are calculated through the use of sum rules. A comparison with previous calculations is also made.Fil: Guardiola, R.. Facultad de FĂsica / Dpto de FĂsica AtĂłmica y Nuclear; EspañaFil: Navarro, J.. Csic - Univ. de Valencia / Inst. de FĂsica Corpuscular; EspañaFil: Portesi, Mariela Adelina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentin
The spectra of mixed He-He droplets
The diffusion Monte Carlo technique is used to calculate and analyze the
excitation spectrum of He atoms bound to a cluster of He atoms, by
using a previously determined optimum filling of single-fermion orbits with
well defined orbital angular momentum , spin and parity quantum numbers.
The study concentrates on the energies and shapes of the three kinds of states
for which the fermionic part of the wave function is a single Slater
determinant: maximum or maximum states within a given orbit, and fully
polarized clusters. The picture that emerges is that of systems with strong
shell effects whose binding and excitation energies are essentially determined
over configuration at fixed number of particles and spin, i.e., by the monopole
properties of an effective Hamiltonian.Comment: 14 pages, 15 figure
Translationally invariant treatment of pair correlations in nuclei: II. Tensor correlations
We study the extension of our translationally invariant treatment of few-body
nuclear systems to include tensor forces and correlations. It is shown that a
direct application of our method is not as successful for realistic V6
interactions as our previous results for V4 potentials suggested. We
investigate the cause in detail for the case of He, and show that a
combination of our method with that of Jastrow-correlated wave functions seems
to be a lot more powerful, thereby suggesting that for mildly to strongly
repulsive forces such a hybrid procedure may be an appropriate description.Comment: 19 pages, 3 ps figures. uses elsart, graphicx, amssym
The importance of time in referee home bias due to social pressure. Evidence from Spanish football
This paper analyses referee home bias due to social pressure with data from the matches played in the First Division of the Spanish football league between the 2002/03 and 2009/10 seasons. Finally, our main conclusion is that the time the referee has to make a decision does affect the final outcome; while there is no referee home bias when a free kick is awarded, in the case of booking players, when the referee has more time to make a decision, social pressure can influence the final outcome in favour of the home team.Social pressure; crowd effect; referee home bias; sports economics.
Two-dimensional molecular para-hydrogen and ortho-deuterium at zero temperature
We study molecular para-hydrogen (p-) and ortho-deuterium
(o-) in two dimensions and in the limit of zero temperature by
means of the diffusion Monte Carlo method. We report energetic and structural
properties of both systems like the total and kinetic energy per particle,
radial pair distribution function, and Lindemann's ratio in the low pressure
regime. By comparing the total energy per particle as a function of the density
in liquid and solid p-, we show that molecular para-hydrogen, and
also ortho-deuterium, remain solid at zero temperature. Interestingly, we
assess the quality of three different symmetrized trial wave functions, based
on the Nosanow-Jastrow model, in the p- solid film at the
variational level. In particular, we analyze a new type of symmetrized trial
wave function which has been used very recently to describe solid He and
found that also characterizes hydrogen satisfactorily. With this wave function,
we show that the one-body density matrix of solid p- possesses off-diagonal long range order, with a condensate fraction
that increases sizably in the negative pressure regime.Comment: 11 pages, 9 figure
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