41,175 research outputs found
Relativistic Mean-Field and Beyond Approaches for Deformed Hypernuclei
We report the recent progress in relativistic mean-field (RMF) and beyond
approaches for the low-energy structure of deformed hypernuclei. We show that
the hyperon with orbital angular momentum (or )
generally reduces (enhances) nuclear quadrupole collectivity. The beyond
mean-field studies of hypernuclear low-lying states demonstrate that there is
generally a large configuration mixing between the two components and in the hypernuclear states. The mixing weight
increases as the collective correlation of nuclear core becomes stronger.
Finally, we show how the energies of hypernuclear low-lying states are
sensitive to parameters in the effective interaction, the
uncertainty of which has a large impact on the predicted maximal mass of
neutron stars.Comment: 12 pages, 7 figures. A plenary talk given at the 13th International
Conference on Hypernuclear and Strange Particle Physics, June 24-29, 2018,
Portsmouth, V
Disappearance of nuclear deformation in hypernuclei: a perspective from a beyond-mean-field study
The previous mean-field calculation [Myaing Thi Win and K. Hagino, Phys. Rev.
C{\bf 78}, 054311 (2008)] has shown that the oblate deformation in
Si disappears when a particle is added to these nuclei.
We here investigate this phenomenon by taking into account the effects beyond
the mean-field approximation. To this end, we employ the microscopic
particle-rotor model based on the covariant density functional theory. We show
that the deformation of Si does not completely disappear, even though it
is somewhat reduced, after a particle is added if the
beyond-mean-field effect is taken into account. We also discuss the impurity
effect of particle on the electric quadrupole transition, and show
that an addition of a particle leads to a reduction in the
value, as a consequence of the reduction in the deformation parameter.Comment: 6 pages, 5 figures. The version to appear in Phys. Rev.
Final Report: Wall Effects in Cavity Flows
The wall effects in cavity flows past an arbitrary two-dimensional body is investigated for both pure-drag and lifting cases based on an inviscid nonlinear flow theory. The over-all features of various theoretical flow models for inviscid cavity flows under the wall effects are discussed from the general momentum consideration in comparison with typical viscous, incompressible wake flows in a channel. In the case of pure drag cavity flows, three theoretical models in common use, namely, the open-wake, Riabouchinsky and re-entrant jet models, are applied to evaluate the solution. Methods of numerical computation are discussed for bodies of arbitrary shape, and are carried out in detail for wedges of all angles. The final numerical results are compared between the different flow models, and the differences pointed out. Further analysis of the results has led to development of several useful formulas for correcting the wall effect. In the lifting flow case, the wall effect on the pressure and hydrodynamic forces acting on arbitrary body is formulated for the choked cavity flow in a closed water tunnel of arbitrary shape, and computed for the flat plate with a finite cavity in a straight tunnel
HOW SUCCESSFUL ARE GOVERNMENT INTERVENTIONS IN FOOD MARKETS? INSIGHTS FROM THE PHILIPPINE RICE MARKET
We investigate the Philippine government's price stabilization policy for rice. Seemingly Unrelated Regressions are used to examine the effectiveness of the program at regional and national levels over a 21-year period (January 1983 to December 2003). Results of the regional analysis indicate some NFA-induced spatial and temporal differences in terms of producer prices. The NFA successfully increased producer prices in 5 of 13 regions through stock accumulation and paddy rice purchase at floor prices. NFA stock releases do not correlate strongly with retail prices at the national level, although results from the regional model indicate that NFA stock releases reduced retail prices in five regions, leading to perceptible spatial and temporal differences between regions. Although the NFA support price appears to have been moderately successful in increasing producer prices at a national level, on average, the support price led to an increase in consumer prices in ten regions and contributed little to price stabilization. Overall, therefore, our results indicate very limited success on the part of the NFA to achieve its major objectives at either regional or national level. We suggest the NFA should concentrate its resources in the poorest areas of the country, where it might exert greater and more useful influence in smaller and locally thin rice markets.Marketing,
Energy Density Functional analysis of shape evolution in N=28 isotones
The structure of low-energy collective states in proton-deficient N=28
isotones is analyzed using structure models based on the relativistic energy
density functional DD-PC1. The relativistic Hartree-Bogoliubov model for
triaxial nuclei is used to calculate binding energy maps in the
- plane. The evolution of neutron and proton single-particle
levels with quadrupole deformation, and the occurrence of gaps around the Fermi
surface, provide a simple microscopic interpretation of the onset of
deformation and shape coexistence. Starting from self-consistent constrained
energy surfaces calculated with the functional DD-PC1, a collective Hamiltonian
for quadrupole vibrations and rotations is employed in the analysis of
excitation spectra and transition rates of Ar, S, and Si.
The results are compared to available data, and previous studies based either
on the mean-field approach or large-scale shell-model calculations. The present
study is particularly focused on S, for which data have recently been
reported that indicate pronounced shape coexistence.Comment: 31 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1102.419
Ab Initio Treatment of Collective Correlations and the Neutrinoless Double Beta Decay of Ca
Working with Hamiltonians from chiral effective field theory, we develop a
novel framework for describing arbitrary deformed medium-mass nuclei by
combining the in-medium similarity renormalization group with the generator
coordinate method. The approach leverages the ability of the first method to
capture dynamic correlations and the second to include collective correlations
without violating symmetries. We use our scheme to compute the matrix element
that governs the neutrinoless double beta decay of Ca to Ti, and
find it to have the value , near or below the predictions of most
phenomenological methods. The result opens the door to ab initio calculations
of the matrix elements for the decay of heavier nuclei such as Ge,
Te, and Xe.Comment: 6 pages, 4 figures and 1 table. supplementary material included.
version to be publishe
Short-wavelength fiber Raman laser pulse-pumped by multimode laser diode at 806 nm
We demonstrate a fiber Raman laser emitting at 835 nm when pumped by bursts of 50 - 100 ns pulses from a multi-mode laser diode at 806 nm. The slope efficiency reaches 38%
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