1,573 research outputs found
String creation in D6-brane background
The production of string charge during a crossing of certain oriented
D-branes is studied. We compute the string charge in the system of a probe
D2-brane and a background D6-brane by use of the equations of motion in the
ten-dimensions. We confirm the creation of string charge as inflow from the
background D6-brane.Comment: 11 pages, 1 figure, typos correcte
Gauge-Invariant Formulation of Adiabatic Self-Consistent Collective Coordinate Method
The adiabatic self-consistent collective coordinate (ASCC) method is a
practical microscopic theory of large-amplitude collective motions in nuclei
with superfluidity. We show that its basic equations are invariant against
transformations involving the gauge angle in the particle-number space. By
virtue of this invariance, a clean separation between the large-amplitude
collective motion and the pairing rotational motion can be achieved, enabling
us to restore the particle-number symmetry broken by the
Hartree-Fock-Bogoliubov (HFB) approximation. We formulate the ASCC method
explicitly in a gauge-invariant form. In solving the ASCC equations, it is
necessary to fix the gauge. Applying this new formulation to the multi-O(4)
model, we compare different gauge-fixing procedures and demonstrate that
calculations using different gauges indeed yield the same results for
gauge-invariant quantities, such as the collective path and quantum spectra. We
suggest a gauge-fixing prescription that seems most convenient in realistic
calculations.Comment: 27 pages, 7 figures, submitted to Prog. Theor. Phy
Effects of Time-Odd Components in Mean Field on Large Amplitude Collective Dynamics
We apply the adiabatic self-consistent collective coordinate (ASCC) method to
the multi-O(4) model and study collective mass (inertia function) of the
many-body tunneling motion. Comparing results with those of the exact
diagonalization, we show that the ASCC method succeeds in describing gradual
change of excitation spectra from an anharmonic vibration about the spherical
shape to a doublet pattern associated with a deformed double-well potential
possessing the oblate-prolate symmetry. The collective mass is significantly
increased by the quadrupole-pairing contribution to time-odd components of the
moving mean field. In contrast, the cranking (Inglis-Belyaev) mass based on the
constrained mean field, which ignores the time-odd components, is smaller than
the ASCC mass and fails to reproduce the exact spectra.Comment: 32 pages, 9 figure
Television-watching in the early years of life and the association with parents’ concerns about decreased visual acuity in their elementary school-aged child: results of a nationwide population-based longitudinal survey of Japan
Purpose
To study the association between television-watching in the earlier years of life and subsequent parents’ concerns about decreased visual acuity in their elementary school-aged child.
Study design
Population-based longitudinal cohort.
Methods
Television-watching and its daily duration, as the main exposure, and parents’ concerns for their child’s decreased visual acuity during the school years, as the main outcome, were picked up from yearly questionnaires performed for the Longitudinal Survey of Newborns in the Twenty-First Century involving all babies born in Japan during either of two periods: between January 10 and 17, 2001 or between July 10 and 17, 2001 (N = 47,015).
Results
Television-/video-watching as the main form of play of children at the ages of 1.5 years and 2.5 years was significantly associated with parents’ concerns for their child’s decreased visual acuity raised once or more in six surveys conducted between the ages of 7 and 12 years (odds ratio, 1.1 and 1.09; 95% CI 1.05–1.15 and 1.04–1.14, respectively). The association remained significant after adjustment for confounding variables, including child’s sex, preterm birth, multiple birth, mother’s age at delivery, mother’s and father’s education, and residential area. Longer daily duration of television-watching at 2.5 years was significantly associated with concerns for the child’s decreased visual acuity between the ages of 7 and 12 years, but not at the ages of 3.5, 4.5, and 5.5 years. The association remained significant in a sensitivity analysis of 28,820 children who participated in all six surveys.
Conclusions
Longer daily exposure to television in children in the earlier years of life was associated with parents’ subsequent concerns about decreased visual acuity in their elementary school-aged child
Microscopic description of large-amplitude shape-mixing dynamics with local QRPA inertial functions
We introduce a microscopic approach to derive all the inertial functions in
the five-dimensional quadrupole collective Hamiltonian. Local normal modes are
evaluated on the constrained mean field in the quasiparticle random-phase
approximation in order to derive the inertial functions. The collective
Hamiltonians for neutron-rich Mg isotopes are determined with use of this
approach, and the shape coexistence/mixing around the N = 20 region is
analyzed.Comment: 6 pages, 2 figures, Talk given at International Symposium New Faces
of Atomic Nuclei, Okinawa, Japan, Nov. 15-17, 201
Collective Path Connecting the Oblate and Prolate Local Minima in 68Se
By means of the adiabatic self-consistent collective coordinate method and
the pairing plus quadrupole interaction, we have obtained the selfconsistent
collective path connecting the oblate and prolate local minima in 68Se for the
first time. Along the collective path, the triaxial deformation parameter
(gamma) changes between 0 and 60 (degree) keeping the axially symmetric
deformation parameter (beta) approximately constant, indicating the importance
of triaxial deformation dynamics in the oblate-prolate shape coexistence
phenomena.Comment: 6 pages including 6 eps figure
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