920 research outputs found

### Anomalous population of $^{10}$He states in reactions with $^{11}$Li

Structure with the lowest energy observed in the $^{10}$He spectrum populated
in the proton knockout reaction with $^{11}$Li beam has a peak at $1.2-1.5$
MeV. This peak is usually interpreted as a resonant $0^+$ ground state of
$^{10}$He. Our theoretical calculations indicate that this peak is likely to be
a pileup of $1^-$, $0^+$, and $2^+$ excitations with very similar shapes. %We
predict a very specific nature of the $1^-$ excitation in $^{10}$He. Moreover,
the ``soft'' $1^-$ excitation appears to be the lowest one in energy. Such an
anomalous continuum response is traced to the halo structure of $^{11}$Li
providing extreme low energy shift to all the expected continuum excitations.
Competitions of the initial state structure (ISS) and the final state
interaction (FSI) effects on the spectrum and three-body correlations in
$^{10}$He are discussed. Analogous effect of the extreme low-energy shift could
also be expected in other cases of $2n$ emitters populated in reactions with
halo nuclei. Simplified example of the $^{10}$He spectrum in $\alpha$ knockout
from $^{14}$Be, is given. We also discuss limits on the properties of $^{9}$He
stemming from the observed $^{10}$He spectrum.Comment: 10 pages, 13 figure

### Scattering theory with finite-gap backgrounds: Transformation operators and characteristic properties of scattering data

We develop direct and inverse scattering theory for Jacobi operators (doubly
infinite second order difference operators) with steplike coefficients which
are asymptotically close to different finite-gap quasi-periodic coefficients on
different sides. We give necessary and sufficient conditions for the scattering
data in the case of perturbations with finite second (or higher) moment.Comment: 23 page

### Two-proton radioactivity and three-body decay. V. Improved momentum distributions

Nowadays quantum-mechanical theory allows one to reliably calculate the
processes of 2p radioactivity (true three-body decays) and the corresponding
energy and angular correlations up to distances of the order of 1000 fm.
However, the precision of modern experiments has now become sufficient to
indicate some deficiency of the predicted theoretical distributions. In this
paper we discuss the extrapolation along the classical trajectories as a method
to improve the convergence of the theoretical energy and angular correlations
at very large distances (of the order of atomic distances), where only the
long-range Coulomb forces are still operating. The precision of this approach
is demonstrated using the "exactly" solvable semianalytical models with
simplified three-body Hamiltonians. It is also demonstrated that for heavy 2p
emitters, the 2p decay momentum distributions can be sensitive to the effect of
the screening by atomic electrons. We compare theoretical results with
available experimental data.Comment: 13 pages, 18 figure

### Scattering Theory for Jacobi Operators with Steplike Quasi-Periodic Background

We develop direct and inverse scattering theory for Jacobi operators with
steplike quasi-periodic finite-gap background in the same isospectral class. We
derive the corresponding Gel'fand-Levitan-Marchenko equation and find minimal
scattering data which determine the perturbed operator uniquely. In addition,
we show how the transmission coefficients can be reconstructed from the
eigenvalues and one of the reflection coefficients.Comment: 14 page

### Azimuthal modulation of the event rate of cosmic ray extensive air showers by the geomagnetic field

The Earth's magnetic field effect on the azimuthal distribution of extensive
air showers (EAS) of cosmic rays has been evaluated using a bulk of the Yakutsk
array data. The uniform azimuthal distribution of the EAS event rate is
rejected at the significance level 10^(-14). Amplitude of the first harmonics
of observed distribution depends on zenith angle as A1=0.2*sin^2(theta) and is
almost independent of the primary energy; the phase coincides with the magnetic
meridian. Basing upon the value of measured effect, the correction factor has
been derived for the particle density depending on a geomagnetic parameter of a
shower.Comment: 4 pages, 3 figures in ps file

### Wildfire propagation modelling

Wildfires are a concrete problem with a strong impact on human life, property and the environment, because
they cause disruption and are an important source of pollutants. Climate change and the legacy of poor management are responsible for wildfires increasing in occurrence and in extension of the burned area. Wildfires
are a challenging task for research, mainly because of their multi-scale and multi-disciplinary nature. Wildfire
propagation is studied in the literature by two alternative approaches: the reaction-diffusion equation and the
front tracking level-set method. The solution of the reaction-diffusion equation is a smooth function with an
infinite domain, while the level-set method generates a sharp function that is not zero inside a compact domain.
However, these two approaches can indeed be considered complementary and reconciled. With this purpose
we derive a method based on the idea to split the motion of the front into a drifting part and a fluctuating
part. This splitting allows specific numerical and physical choices that can improve the models. In particular,
the drifting part can be provided by chosen existing method (e.g. one based on the level-set method) and this
permits the choice for the best drifting part. The fluctuating part is the result of a comprehensive statistical
description of the physics of the system and includes the random effects, e.g., turbulent hot-air transport and
fire-spotting. As a consequence, the fluctuating part can have a non-zero mean (for example, due to ember
jump lengths), which means that the drifting part does not correspond to the average motion. This last fact
distinguishes between the present splitting and the well-known Reynolds decomposition adopted in turbulence
studies. Actually, the effective front emerges to be the weighted superposition of drifting fronts according to
the probability density function of the fire-line displacement by random effects. The resulting effective process
emerges to be governed by an evolution equation of the reaction-diffusion type. In this reconciled approach,
the rate of spread of the fire keeps the same key and characterising role that is typical in the level-set approach.
Moreover, the model emerges to be suitable for simulating effects due to turbulent convection, such as fire
flank and backing fire, the faster fire spread being because of the actions by hot-air pre-heating and by ember
landing, and also due to the fire overcoming a fire-break zone, which is a case not resolved by models based on the
level-set method. A physical parametrization of fire-spotting is also proposed and numerical simulations are shown.PhD Grant "La Caixa 2014

### From Coulomb excitation cross sections to non-resonant astrophysical rates in three-body systems: $^{17}$Ne case

Coulomb and nuclear dissociation of $^{17}$Ne on light and heavy targets are
studied theoretically. The dipole E1 strength function is determined in a broad
energy range including energies of astrophysical interest. Dependence of the
strength function on different parameters of the $^{17}$Ne ground state
structure and continuum dynamics is analyzed in a three-body model. The
discovered dependence plays an important role for studies of the strength
functions for the three-body E1 dissociation and radiative capture. The
constraints on the $[s^2]/[d^2]$ configuration mixing in $^{17}$Ne and on
$p$-wave interaction in the $^{15}$O+$p$ channel are imposed based on
experimental data for $^{17}$Ne Coulomb dissociation on heavy target.Comment: 12 pages, 13 figure

### THE OPTIMAL PRINCIPLE OF BELLMAN IN THE PROBLEM OF OPTIMAL MEANS DISTRIBUTION BETWEEN ENTERPRISES FOR THE EXPANSION OF PRODUCTION

The method of dynamic programming has been considered, which is used in solving multiple problems in economics, on the example of using Bellman’s optimality principle for solving nonlinear programming problems. On a specific numerical example, the features of the solution have been shown in detail with all the calculations. The problem of optimal distribution of funds among enterprises for the expansion of production has been formulated, which would give the maximum total increase in output. The solution of the task has been presented in the case, when the number of enterprises is 3. It has been shown, that the Bellman optimality principle allows you solve applied problems of cost forecasting with obtaining the optimal solution-maximum profit at minimum costs

### Beauty and standard appearance under globalization

This article deals with the perception of normative appearance in the conditions of culture globalization, and raises the question of the relationship between appearance and cultural identity in the context of globalizing processesРассматриваются вопросы восприятия нормативной внешности в условиях глобализации культуры, а также поднимается вопрос о соотношении внешности и культурной идентичности в контексте глобализирующих процессо

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