1,165 research outputs found

    Regularities with random interactions in energy centroids defined by group symmetries

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    Regular structures generated by random interactions in energy centroids defined over irreducible representations (irreps) of some of the group symmetries of the interacting boson models sdsdIBM, sdgsdgIBM, sdsdIBM-TT and sdsdIBM-STST are studied by deriving trace propagations equations for the centroids. It is found that, with random interactions, the lowest and highest group irreps in general carry most of the probability for the corresponding centroids to be lowest in energy. This generalizes the result known earlier, via numerical diagonalization, for the more complicated fixed spin (JJ) centroids where simple trace propagation is not possible.Comment: 18 pages, 3 figure

    Random matrix ensemble with random two-body interactions in presence of a mean-field for spin one boson systems

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    For mm number of bosons, carrying spin (SS=1) degree of freedom, in Ω\Omega number of single particle orbitals, each triply degenerate, we introduce and analyze embedded Gaussian orthogonal ensemble of random matrices generated by random two-body interactions that are spin (S) scalar [BEGOE(2)-S1S1]. The embedding algebra is U(3)⊃G⊃G1⊗SO(3)U(3) \supset G \supset G1 \otimes SO(3) with SO(3) generating spin SS. A method for constructing the ensembles in fixed-(mm, SS) space has been developed. Numerical calculations show that the form of the fixed-(mm, SS) density of states is close to Gaussian and level fluctuations follow GOE. Propagation formulas for the fixed-(mm, SS) space energy centroids and spectral variances are derived for a general one plus two-body Hamiltonian preserving spin. In addition to these, we also introduce two different pairing symmetry algebras in the space defined by BEGOE(2)-S1S1 and the structure of ground states is studied for each paring symmetry.Comment: 22 pages, 6 figure

    Constraining nuclear physics parameters with current and future COHERENT data

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    Motivated by the recent observation of coherent elastic neutrino-nucleus scattering (CEν\nu NS) at the COHERENT experiment, our goal is to explore its potential in probing important nuclear structure parameters. We show that the recent COHERENT data offers unique opportunities to investigate the neutron nuclear form factor. Our present calculations are based on the deformed Shell Model (DSM) method which leads to a better fit of the recent CEν\nu NS data, as compared to known phenomenological form factors such as the Helm-type, symmetrized Fermi and Klein-Nystrand. The attainable sensitivities and the prospects of improvement during the next phase of the COHERENT experiment are also considered and analyzed in the framework of two upgrade scenarios.Comment: 13 pages, 5 figures, 2 tables; v2: minor corrections, version to appear in PL

    Half-lives and pre-supernova weak interaction rates for nuclei away from the stability line

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    A detailed model for the calculation of beta decay rates of the fpfp shell nuclei for situations prevailing in pre-supernova and collapse phases of evolution of the core of massive stars leading to supernova explosion has been extended for electron-capture rates. It can also be used to determine the half-lives of neutron-rich nuclei in the fp/fpgfp/fpg shell. The model uses an averaged Gamow-Teller (GT) strength function. But it can also use the experimental log ft values and GT strength function from (n,p)(n,p) reaction studies wherever available. The calculated rate includes contributions from each of the low-lying excited states of the mother including some specific resonant states ("back resonance") having large GT matrix elements.Comment: 11 pages; Latex; no figs; version to appear in J. Phys.

    O(12) limit and complete classification of symmetry schemes in proton-neutron interacting boson model

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    It is shown that the proton-neutron interacting boson model (pnIBM) admits new symmetry limits with O(12) algebra which break F-spin but preserves the quantum number M_F. The generators of O(12) are derived and the quantum number `v' of O(12) for a given boson number N is determined by identifying the corresponding quasi-spin algebra. The O(12) algebra generates two symmetry schemes and for both of them, complete classification of the basis states and typical spectra are given. With the O(12) algebra identified, complete classification of pnIBM symmetry limits with good M_F is established.Comment: 22 pages, 1 figur

    Health insurance coverage and maternal healthcare services utilization in Jordan: evidence from the 2017–18 Jordan demographic and health survey

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    Background Despite the relationship between health insurance coverage and maternal healthcare services utilization, previous studies in Jordan on the use of maternal healthcare services have mainly focused on patterns and determinants of maternal healthcare services utilization in Jordan. Therefore, this study investigated the relationship between health insurance coverage and maternal healthcare services utilization in Jordan. Methods This study used secondary data published in 2017-18 Jordan Demographic and Health Survey on 4656 women of reproductive age (15–49 years). The independent variable was health insurance coverage and the outcome variable was maternal healthcare services utilization, measured through timing of first antenatal visit, four or more antenatal care visits, and skilled birth attendance. The data were analyzed using descriptive statistics and binary logistic regression. Results Out of the total number of women who participated in the study, 38.2% were not covered by health insurance. With maternal healthcare utilization, 12.5%, 23.2%, and 10.1% respectively, failed to make early first antenatal care visit, complete four or more antenatal care visits and have their delivery attended by a skilled worker. After controlling for the socio-demographic factors, health insurance coverage was associated with increased odds of early timing of first antenatal care visits and completion of four or more antenatal care visits (aOR = 1.33, p < 0.05, aOR = 1.25, p < 0.01, respectively). However, women who were covered by health insurance were less likely to use skilled birth attendance during delivery (aOR = 0.72 p < 0.001). Conclusions Jordanian women with health insurance coverage were more likely to have early first antenatal care visits and complete four or more antenatal care visits. However, they were less likely to have their delivery attended by a skilled professional. This study provides evidence that health insurance coverage has contributed to increased maternal healthcare services utilization, only in terms of number and timing of antenatal care visits in Jordan. It is recommended that policy makers in Jordan should strengthen the coverage of health insurance in the country, especially among women of reproductive age in order to enhance the use of maternal healthcare services in the country

    One plus two-body random matrix ensembles with parity: Density of states and parity ratios

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    One plus two-body embedded Gaussian orthogonal ensemble of random matrices with parity [EGOE(1+2)-π\pi] generated by a random two-body interaction (modeled by GOE in two particle spaces) in the presence of a mean-field, for spinless identical fermion systems, is defined, generalizing the two-body ensemble with parity analyzed by Papenbrock and Weidenm\"{u}ller [Phys. Rev. C {\bf 78}, 054305 (2008)], in terms of two mixing parameters and a gap between the positive (π=+)(\pi=+) and negative (π=−)(\pi=-) parity single particle (sp) states. Numerical calculations are used to demonstrate, using realistic values of the mixing parameters appropriate for some nuclei, that the EGOE(1+2)-π\pi ensemble generates Gaussian form (with corrections) for fixed parity eigenvalue densities (i.e. state densities). The random matrix model also generates many features in parity ratios of state densities that are similar to those predicted by a method based on the Fermi-gas model for nuclei. We have also obtained, by applying the formulation due to Chang et al [Ann. Phys. (N.Y.) {\bf 66}, 137 (1971)], a simple formula for the spectral variances defined over fixed-(m1,m2)(m_1,m_2) spaces, where m1m_1 is the number of fermions in the +ve parity sp states and m2m_2 is the number of fermions in the -ve parity sp states. Similarly, using the binary correlation approximation, in the dilute limit, we have derived expressions for the lowest two shape parameters. The smoothed densities generated by the sum of fixed-(m1,m2)(m_1,m_2) Gaussians with lowest two shape corrections describe the numerical results in many situations. The model also generates preponderance of +ve parity ground states for small values of the mixing parameters and this is a feature seen in nuclear shell model results.Comment: 38 pages, 11 figures, 3 tables, enlarged and reorganized with additional result
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