4,305 research outputs found
Microscopic Description of Nuclear Wobbling Motion -- Rotation of traxially deformed nuclei --
The nuclear wobbling motion in the Lu region is studied by the microscopic
cranked mean-field plus RPA method. The Woods-Saxon potential is used as a
mean-field with a new parameterization which gives reliable description of
rapidly rotating nuclei. The prescription of symmetry-preserving residual
interaction makes the calculation of the RPA step parameter-free, and we find
the wobbling-like RPA solution if the triaxial deformation of the mean-field is
suitably chosen. It is shown that the calculated out-of-band of the
wobbling-like solution depends on the triaxial deformation in the same way as
in the macroscopic rotor model, and can be used to probe the triaxiality of the
nuclear mean-field.Comment: 10 pages, 8 figures, talk at International Conference on Nuclear
Structure Physics, Shanghai, June 200
Drag force on an oscillating object in quantum turbulence
This paper reports results of the computation of the drag force exerted on an
oscillating object in quantum turbulence in superfluid He. The drag force
is calculated on the basis of numerical simulations of quantum turbulent flow
about the object. The drag force is proportional to the square of the magnitude
of the oscillation velocity, which is similar to that in classical turbulence
at high Reynolds number. The drag coefficient is also calculated, and its value
is found to be of the same order as that observed in previous experiments. The
correspondence between quantum and classical turbulences is further clarified
by examining the turbulence created by oscillating objects.Comment: 7 pages, 5 figures, 1 tabl
Multi-command Tactile Brain Computer Interface: A Feasibility Study
The study presented explores the extent to which tactile stimuli delivered to
the ten digits of a BCI-naive subject can serve as a platform for a brain
computer interface (BCI) that could be used in an interactive application such
as robotic vehicle operation. The ten fingertips are used to evoke
somatosensory brain responses, thus defining a tactile brain computer interface
(tBCI). Experimental results on subjects performing online (real-time) tBCI,
using stimuli with a moderately fast inter-stimulus-interval (ISI), provide a
validation of the tBCI prototype, while the feasibility of the concept is
illuminated through information-transfer rates obtained through the case study.Comment: Haptic and Audio Interaction Design 2013, Daejeon, Korea, April
18-19, 2013, 15 pages, 4 figures, The final publication will be available at
link.springer.co
Topology conserving gauge action and the overlap-Dirac operator
We apply the topology conserving gauge action proposed by Luescher to the
four-dimensional lattice QCD simulation in the quenched approximation. With
this gauge action the topological charge is stabilized along the hybrid Monte
Carlo updates compared to the standard Wilson gauge action. The quark potential
and renormalized coupling constant are in good agreement with the results
obtained with the Wilson gauge action. We also investigate the low-lying
eigenvalue distribution of the hermitian Wilson-Dirac operator, which is
relevant for the construction of the overlap-Dirac operator.Comment: 27pages, 11figures, accepted versio
Polarization proximity effect in isolator crystal pairs
We experimentally studied the polarization dynamics (orientation and
ellipticity) of near infrared light transmitted through magnetooptic Yttrium
Iron Garnet crystal pairs using a modified balanced detection scheme. When the
pair separation is in the sub-millimeter range, we observed a proximity effect
in which the saturation field is reduced by up to 20%. 1D magnetostatic
calculations suggest that the proximity effect originates from magnetostatic
interactions between the dipole moments of the isolator crystals. This
substantial reduction of the saturation field is potentially useful for the
realization of low-power integrated magneto-optical devices.Comment: submitted to Optics Letter
Parametrizations of triaxial deformation and E2 transitions of the wobbling band
By the very definition the triaxial deformation parameter is related
to the expectation values of the K=0 and K=2 components of the intrinsic
quadrupole tensor operator. On the other hand, using the same symbol
"", various different parametrizations of triaxial deformation have
been employed, which are suitable for various types of the mean-field
potentials. It is pointed out that the values of various "" are quite
different for the same actual triaxial deformation, especially for the large
deformation; for example, the difference can be almost a factor two for the
case of the triaxial superdeformed bands recently observed in the Hf and Lu
nuclei. In our previous work, we have studied the wobbling band in Lu nuclei by
using the microscopic framework of the cranked Nilsson mean-field and the
random phase approximation, where the most serious problem is that the
calculated B(E2) value is about factor two smaller. It is shown that the origin
of this underestimation can be mainly attributed to the small triaxial
deformation; if is used the same triaxial deformation as in the analysis of the
particle-rotor model, the calculated B(E2) increases and gives correct
magnitude compared with the experimental data.Comment: 10 pages, 9 figure
Spin-Wave Description of Nuclear Spin-Lattice Relaxation in Mn_{12}O_{12} Acetate
In response to recent nuclear-magnetic-resonance (NMR) measurements on the
molecular cluster Mn_{12}O_{12} acetate, we study the nuclear spin-lattice
relaxation rate 1/T_1 developing a modified spin-wave theory. Our microscopic
new approach, which is distinct from previous macroscopic treatments of the
cluster as a rigid spin of S=10, not only excellently interprets the observed
temperature and applied-field dependences of 1/T_1 for ^{55}Mn nuclei but also
strongly supports the ^{13}C NMR evidence for spin delocalization over the
entire molecule.Comment: to be published in Phys. Rev. Lett., 4 pages, 4 figures embedde
Cohomology of the minimal nilpotent orbit
We compute the integral cohomology of the minimal non-trivial nilpotent orbit
in a complex simple (or quasi-simple) Lie algebra. We find by a uniform
approach that the middle cohomology group is isomorphic to the fundamental
group of the sub-root system generated by the long simple roots. The modulo
reduction of the Springer correspondent representation involves the sign
representation exactly when divides the order of this cohomology group.
The primes dividing the torsion of the rest of the cohomology are bad primes.Comment: 29 pages, v2 : Leray-Serre spectral sequence replaced by Gysin
sequence only, corrected typo
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