261 research outputs found
Linear response theory in the continuum for deformed nuclei: Green's function vs. time-dependent Hartree-Fock with the absorbing-boundary condition
The continuum random-phase approximation is extended to the one applicable to
deformed nuclei. We propose two different approaches. One is based on the use
of the three dimensional (3D) Green's function and the other is the
small-amplitude TDHF with the absorbing-boundary condition. Both methods are
based on the 3D Cartesian grid representation and applicable to systems without
any symmetry on nuclear shape. The accuracy and identity of these two methods
are examined with the BKN interaction. Using the full Skyrme energy functional
in the small-amplitude TDHF approach, we study the isovector giant dipole
states in the continuum for O-16 and for even-even Be isotopes.Comment: 15 pages, 8 figure
Microscopic approach to large-amplitude deformation dynamics with local QRPA inertial masses
We have developed a new method for determining microscopically the
fivedimensional quadrupole collective Hamiltonian, on the basis of the
adiabatic self-consistent collective coordinate method. This method consists of
the constrained Hartree-Fock-Bogoliubov (HFB) equation and the local QRPA
(LQRPA) equations, which are an extension of the usual QRPA (quasiparticle
random phase approximation) to non-HFB-equilibrium points, on top of the CHFB
states. One of the advantages of our method is that the inertial functions
calculated with this method contain the contributions of the time-odd
components of the mean field, which are ignored in the widely-used cranking
formula. We illustrate usefulness of our method by applying to oblate-prolate
shape coexistence in 72Kr and shape phase transition in neutron-rich Cr
isotopes around N=40.Comment: 6pages, talk given at Rutherford Centennial Conference on Nuclear
Physics, 8 - 12 August 2011, The University of Mancheste
From bad metal to Kondo insulator:Temperature evolution of the optical properties of SmB6
The recent rekindling of interest in the mixed valent Kondo insulator
SmB as candidate for a first correlated topological insulator has
resulted in a wealth of new experimental observations. In particular,
angle-resolved photoemission experiments have provided completely new insights
into the formation of the low temperature Kondo insulating state starting from
the high temperature correlated metal. Here, we report detailed temperature and
energy dependent measurements of the optical constants of SmB in order to
provide a detailed study from the point of view of a bulk sensitive
spectroscopic probe. We detect a previously unobserved infrared active optical
phonon mode, involving the movement of the Sm ions against the boron cages. The
changes taking place in the free carrier response with temperature and their
connection to changes in optical transitions between different bands are
discussed. We find that the free charge density starts to decrease rapidly
below approximately 200 K. Below 60 K a small amount of spectral weight begins
to accumulate in low lying interband transitions, indicating the formation of
the Kondo insulating state; however, the total integrated spectral weight in
our experimental window ( eV) decreases. This indicates the
involvement of a large Coulomb interaction ( 5 eV) in the formation of the
Kondo insulator.Comment: 10 pages, 7 figures (including supp.). Accepted for publication in
New Journal of Physic
Application of Absorbing Boundary Condition to Nuclear Breakup Reactions
Absorbing boundary condition approach to nuclear breakup reactions is
investigated. A key ingredient of the method is an absorbing potential outside
the physical area, which simulates the outgoing boundary condition for
scattered waves. After discretizing the radial variables, the problem results
in a linear algebraic equation with a sparse coefficient matrix, to which
efficient iterative methods can be applicable. No virtual state such as
discretized continuum channel needs to be introduced in the method. Basic
aspects of the method are discussed by considering a nuclear two-body
scattering problem described with an optical potential. We then apply the
method to the breakup reactions of deuterons described in a three-body direct
reaction model. Results employing the absorbing boundary condition are found to
accurately coincide with those of the existing method which utilizes
discretized continuum channels.Comment: 21 pages, 5 figures, RevTeX
Decoupling carrier concentration and electron-phonon coupling in oxide heterostructures observed with resonant inelastic x-ray scattering
We report the observation of multiple phonon satellite features in ultra thin
superlattices of form SrIrO/SrTiO using resonant inelastic x-ray
scattering. As the values of and vary the energy loss spectra show a
systematic evolution in the relative intensity of the phonon satellites. Using
a closed-form solution for the cross section, we extract the variation in the
electron-phonon coupling strength as a function of and . Combined with
the negligible carrier doping into the SrTiO layers, these results indicate
that tuning of the electron-phonon coupling can be effectively decoupled from
doping. This work showcases both a feasible method to extract the
electron-phonon coupling in superlattices and unveils a potential route for
tuning this coupling which is often associated with superconductivity in
SrTiO-based systems.Comment: 4 pages, 5 figure
Relative spins and excitation energies of superdeformed bands in 190Hg: Further evidence for octupole vibration
An experiment using the Eurogam Phase II gamma-ray spectrometer confirms the
existence of an excited superdeformed (SD) band in 190Hg and its very unusual
decay into the lowest SD band over 3-4 transitions. The energies and dipole
character of the transitions linking the two SD bands have been firmly
established. Comparisons with RPA calculations indicate that the excited SD
band can be interpreted as an octupole-vibrational structure.Comment: 12 pages, latex, 4 figures available via WWW at
http://www.phy.anl.gov/bgo/bc/hg190_nucl_ex.htm
Linear Responses in Time-dependent Hartree-Fock-Bogoliubov Method with Gogny Interaction
A numerical method to integrate the time-dependent Hartree-Fock Bogoliubov
(TDHFB) equations with Gogny interaction is proposed. The feasibility of the
TDHFB code is illustrated by the conservation of the energy, particle numbers,
and center-of-mass in the small amplitude vibrations of oxygen 20. The TDHFB
code is applied to the isoscalar quadrupole and/or isovector dipole vibrations
in the linear (small amplitude) region in oxygen isotopes (masses A = 18,20,22
and 24), titanium isotopes (A = 44,50,52 and 54), neon isotope (A = 26), and
magnesium isotopes (A = 24 and 34). The isoscalar quadrupole and isovector
dipole strength functions are calculated from the expectation values of the
isoscalar quadrupole and isovector dipole moments.Comment: 10 pages, 13 figure
Tilted Rotation and Wobbling Motion in Nuclei
The self-consistent harmonic oscillator model including the three-dimensional
cranking term is extended to describe collective excitations in the random
phase approximation. It is found that quadrupole collective excitations
associated with wobbling motion in rotating nuclei lead to the appearance of
two- or three-dimensional rotation.Comment: 9 pages, 2 Postscript figures, corrected typo
Human shoulder development is adapted to obstetrical constraints
ヒトは小さく生まれて大きく育つ --その秘密は鎖骨にあり--. 京都大学プレスリリース. 2022-04-13.In humans, obstetrical difficulties arise from the large head and broad shoulders of the neonate relative to the maternal birth canal. Various characteristics of human cranial development, such as the relatively small head of neonates compared with adults and the delayed fusion of the metopic suture, have been suggested to reflect developmental adaptations to obstetrical constraints. On the other hand, it remains unknown whether the shoulders of humans also exhibit developmental features reflecting obstetrical adaptation. Here we address this question by tracking the development of shoulder width from fetal to adult stages in humans, chimpanzees, and Japanese macaques. Compared with nonhuman primates, shoulder development in humans follows a different trajectory, exhibiting reduced growth relative to trunk length before birth and enhanced growth after birth. This indicates that the perinatal developmental characteristics of the shoulders likely evolved to ease obstetrical difficulties such as shoulder dystocia in humans
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