24,948 research outputs found
Asymptotics of neutron Cooper pair in weakly bound nuclei
Asymptotic form of neutron Cooper pair penetrating to the exterior of nuclear
surface is investigated with the Bogoliubov theory for the superfluid Fermions.
Based on a two-particle Schr\"{o}dinger equation governing the Cooper pair wave
function and systematic studies for both weakly bound and stable nuclei, the
Cooper pair is shown to be spatially correlated even in the asymptotic large
distance limit, and the penetration length of the pair condensate is revealed
to be universally governed by the two-neutron separation energy and
the di-neutron mass
Pair correlation of giant halo nuclei in continuum Skyrme-Hartree-Fock-Bogoliubov theory
The giant halos predicted in neutron-rich Zr isotopes with are
investigated by using the self-consistent continuum Skyrme
Hartree-Fock-Bogoliubov approach, in which the asymptotic behavior of continuum
quasiparticle states is properly treated by the Green's function method. We
study in detail the neutron pair correlation involved in the giant halo by
analyzing the asymptotic exponential tail of the neutron pair condensate (pair
density) in addition to that of the neutron particle density. The neutron
quasiparticle spectra associated with these giant halo nuclei are examined. It
is found that the asymptotic exponential tail of the neutron pair condensate is
dominated by non-resonant continuum quasiparticle states corresponding to the
scattering states with low asymptotic kinetic energy. This is in contrast to
the asymptotic tail of the neutron density, whose main contributions arise from
the resonant quasiparticle states corresponding to the weakly-bound
single-particle orbits and resonance orbits in the Hartree-Fock potential
Generalized MICZ-Kepler Problems and Unitary Highest Weight Modules
For each integer , we demonstrate that a -dimensional
generalized MICZ-Kepler problem has an \mr{Spin}(2, 2n+2) dynamical symmetry
which extends the manifest \mr{Spin}(2n+1) symmetry. The Hilbert space of
bound states is shown to form a unitary highest weight \mr{Spin}(2,
2n+2)-module which occurs at the first reduction point in the
Enright-Howe-Wallach classification diagram for the unitary highest weight
modules. As a byproduct, we get a simple geometric realization for such a
unitary highest weight \mr{Spin}(2, 2n+2)-module.Comment: 27 pages, Refs. update
Impurity effect of Lambda hyperon on collective excitations of atomic nuclei
Taking the ground state rotational band in Mg as an example, we
investigate the impurity effect of hyperon on collective excitations
of atomic nuclei in the framework of non-relativistic energy density functional
theory. To this end, we take into account correlations related to the
restoration of broken symmetries and fluctuations of collective variables by
solving the eigenvalue problem of a five-dimensional collective Hamiltonian for
quadrupole vibrational and rotational degrees of freedom. The parameters of the
collective Hamiltonian are determined with constrained mean-field calculations
for triaxial shapes using the SGII Skyrme force. We compare the low-spin
spectrum for Mg with the spectrum for the same nucleus inside
Mg. It is found that the hyperon stretches the
ground state band and reduces the value by
, mainly by softening the potential energy surface towards the
spherical shape, even though the shrinkage effect on the average proton radius
is only .Comment: 16 pages, 5 figures, and 1 tabl
Courtyard sound field characteristics by bell sounds in Han Chinese Buddhist temples
The acoustic environments of Han Chinese Buddhist temples have long played an important role in the development of Buddhism. This study explored the effects of layouts and spatial elements of Han Chinese Buddhist temples on courtyard sound fields. First, sound fields of three traditional Han Chinese courtyards were measured, and results were compared with sound field simulations to determine the appropriate acoustic and software parameter setting for ancient building materials in the context of sound field simulation. Next, a sound field model for standard forms of Han Chinese Buddhist temples was built and analysed. Results indicate that in traditional Buddhist temples, spatial elements—such as the height and sound absorption coefficient of temple courtyard walls, position of courtyard partition walls, and the position and height of bell towers—could significantly affect the sound pressure level (SPL), reverberation time (RT), and musical clarity (C80) of each courtyard. However, enclosure materials, such as those used in roofs, on the ground, and in windows of Han Chinese Buddhist temples, had relatively small effects on temple courtyard sound fields
Temperature dependence of the resonance and low energy spin excitations in superconducting FeTeSe
We use inelastic neutron scattering to study the temperature dependence of
the low-energy spin excitations in single crystals of superconducting
FeTeSe ( K). In the low-temperature superconducting
state, the imaginary part of the dynamic susceptibility at the electron and
hole Fermi surfaces nesting wave vector ,
, has a small spin gap, a two-dimensional
neutron spin resonance above the spin gap, and increases linearly with
increasing for energies above the resonance. While the intensity
of the resonance decreases like an order parameter with increasing temperature
and disappears at temperature slightly above , the energy of the mode is
weakly temperature dependent and vanishes concurrently above . This
suggests that in spite of its similarities with the resonance in electron-doped
superconducting BaFe(Co,Ni)As, the mode in
FeTeSe is not directly associated with the superconducting
electronic gap.Comment: 7 pages, 6 figure
Pseudospin symmetry in supersymmetric quantum mechanics: Schr\"odinger equations
The origin of pseudospin symmetry (PSS) and its breaking mechanism are
explored by combining supersymmetry (SUSY) quantum mechanics, perturbation
theory, and the similarity renormalization group (SRG) method. The
Schr\"odinger equation is taken as an example, corresponding to the
lowest-order approximation in transforming a Dirac equation into a diagonal
form by using the SRG. It is shown that while the spin-symmetry-conserving term
appears in the single-particle Hamiltonian , the PSS-conserving term appears
naturally in its SUSY partner Hamiltonian . The eigenstates of
Hamiltonians and are exactly one-to-one identical except for
the so-called intruder states. In such a way, the origin of PSS deeply hidden
in can be traced in its SUSY partner Hamiltonian . The
perturbative nature of PSS in the present potential without spin-orbit term is
demonstrated by the perturbation calculations, and the PSS-breaking term can be
regarded as a very small perturbation on the exact PSS limits. A general
tendency that the pseudospin-orbit splittings become smaller with increasing
single-particle energies can also be interpreted in an explicit way.Comment: 31 pages, 11 figures, 2 table
Ticking terahertz wave generation in attoseconds
We perform a joint measurement of terahertz waves and high-order harmonics
generated from noble atoms driven by a fundamental laser pulse and its second
harmonic. By correlating their dependence on the phase-delay of the two pulses,
we determine the generation of THz waves in tens of attoseconds precision.
Compared with simulations and models, we find that the laser-assisted
soft-collision of the electron wave packet with the atomic core plays a key
role. It is demonstrated that the rescattering process, being indispensable in
HHG processes, dominant THz wave generation as well but in a more elaborate
way. The new finding might be helpful for the full characterization of the
rescattering dynamics.Comment: 4 figure
- …