1,622 research outputs found
The interaction between railway vehicle dynamics and track lateral alignment
Track geometry deteriorates with traffic flow, thus it needs to be regularly restored using tamping or other method. As the deterioration is mainly in the vertical direction this aspect has been widely studied and models for its analysis developed, however, the lateral deterioration of track is not as well understood. This research aims to develop a method that can be used to analyse and predict the lateral deterioration of railway track caused by traffic flows, and investigate the influences of different railway vehicles, running speeds, traffic types and wheel/rail contact conditions
P-wave Pentaquark and its Decay in the Quark Model with Instanton Induced Interaction
P-wave pentaquarks with strangeness +1, I=0 and J^P=1/2^+ are studied in the
non-relativistic quark model with instanton induced interaction (III). We
present their mass splittings and orbital-spin-isospin-color structures. It is
found that decompositions of the wave functions are sensitive to III, while the
mass splittings are insensitive. The decay of the lowest energy pentaquark,
\Theta^+, is found to be suppressed when the contribution of III is increased.
Its wave function is dominated by Jaffe-Wilczek-type configuration at large
III.Comment: 9 pages, 5 figure
Effects of Instanton Induced Interaction on the Pentaquarks
Roles of instanton induced interactions (III) in the masses of pentaquark
baryons, Theta^+ (J=1/2 and 3/2) and Xi^{--}, and a dibaryon, H, are discussed
using the MIT bag model in the negative parity case. It is shown that the
two-body terms in III give a strong attraction mainly due to the increase of
the number of pairs in multi-quark systems. In contrast, the three-body u-d-s
interaction is repulsive. It is found that III lowers the mass of Theta^+ as
much as 100 MeV from the mass predicted by the bag model without III.Comment: 11 pages, 3 figure
All-electrical detection of the relative strength of Rashba and Dresselhaus spin-orbit interaction in quantum wires
We propose a method to determine the relative strength of Rashba and
Dresselhaus spin-orbit interaction from transport measurements without the need
of fitting parameters. To this end, we make use of the conductance anisotropy
in narrow quantum wires with respect to the directions of an in-plane magnetic
field, the quantum wire and the crystal orientation. We support our proposal by
numerical calculations of the conductance of quantum wires based on the
Landauer formalism which show the applicability of the method to a wide range
of parameters.Comment: 4 pages, 4 figure
Gauge-Fixing and Residual Symmetries in Gauge/Gravity Theories with Extra Dimensions
We study compactified pure gauge/gravitational theories with gauge-fixing
terms and show that these theories possess quantum mechanical SUSY-like
symmetries between unphysical degrees of freedom. These residual symmetries are
global symmetries and generated by quantum mechanical N=2 supercharges. Also,
we establish new one-parameter family of gauge choices for higher-dimensional
gravity, and calculate as a check of its validity one graviton exchange
amplitude in the lowest tree-level approximation. We confirm that the result is
indeed -independent and the cancellation of the -dependence is
ensured by the residual symmetries. We also give a simple interpretation of the
vDVZ-discontinuity, which arises in the lowest tree-level approximation, from
the supersymmetric point of view.Comment: REVTeX4, 17 pages, 1 figur
Spin echo in spinor dipolar Bose-Einstein condensates
We theoretically propose and numerically realize spin echo in a spinor
Bose--Einstein condensate (BEC). We investigate the influence on the spin echo
of phase separation of the condensate. The equation of motion of the spin
density exhibits two relaxation times. We use two methods to separate the
relaxation times and hence demonstrate a technique to reveal magnetic
dipole--dipole interactions in spinor BECs.Comment: 4 pages, 5 figure
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