3,862 research outputs found
Viscoelastic evaluation of biological soft tissue in crush process at subsonic level for anti-bird strike technology of airplane
Miniaturization and lightening of airplane are advanced to improve its economic efficiency, and the safety technology of airplane design becomes difficult while the accident of bird-strike is increasing year by year. Then a system of shock impact test by using airsoft rifle is developed to evaluate the design technology of anti-bird strike structure of airplane. The viscoelastic characteristics of specimen is evaluated by analyzing stress response using the modified Hertz contact theory and the wave equation at the moment when simple ball bullet is shot to specimen by the airsoft rifle. In the results of experiment, the obvious relationship is observed subjectively between quasi-static and impact responses of specimen. The evaluated viscoelastic relationship is applied to simulate the impact test by using LSDYNA with fundamental viscoelastic constitutive equation and the material parameters derived from the impact test, and the well similar behavior has been simulated by the constitutive equation. By using the developed technology here, the phantom imitating real bird will be developed as standard specimen for an anti-bird strike test in future
Topological Quantum Computing with p-Wave Superfluid Vortices
It is shown that Majorana fermions trapped in three vortices in a p-wave
superfluid form a qubit in a topological quantum computing (TQC). Several
similar ideas have already been proposed: Ivanov [Phys. Rev. Lett. {\bf 86},
268 (2001)] and Zhang {\it et al.} [Phys. Rev. Lett. {\bf 99}, 220502 (2007)]
have proposed schemes in which a qubit is implemented with two and four
Majorana fermions, respectively, where a qubit operation is performed by
exchanging the positions of Majorana fermions. The set of gates thus obtained
is a discrete subset of the relevant unitary group. We propose, in this paper,
a new scheme, where three Majorana fermions form a qubit. We show that
continuous 1-qubit gate operations are possible by exchanging the positions of
Majorana fermions complemented with dynamical phase change. 2-qubit gates are
realized through the use of the coupling between Majorana fermions of different
qubits.Comment: 5 pages, 2 figures. Two-qubit gate implementation is added
Topological Structure of a Vortex in Fulde-Ferrell-Larkin-Ovchinnikov State
We find theoretically that the vortex core in the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is quite different from the
ordinary core by a simple topological reason. The intersection point of a
vortex and nodal plane of the FFLO state empties the excess spins. This leads
to observable consequences in the spatial structure of the spontaneous
magnetization. We analyze this topological structure based on the low lying
excitation spectrum by solving microscopic Bogoliubov-de Gennes equation to
clarify its physical origin.Comment: 4 pages, 4 figure
Vortex structures and zero energy states in the BCS-to-BEC evolution of p-wave resonant Fermi gases
Multiply quantized vortices in the BCS-to-BEC evolution of p-wave resonant
Fermi gases are investigated theoretically. The vortex structure and the
low-energy quasiparticle states are discussed, based on the self-consistent
calculations of the Bogoliubov-de Gennes and gap equations. We reveal the
direct relation between the macroscopic structure of vortices, such as particle
densities, and the low-lying quasiparticle state. In addition, the net angular
momentum for multiply quantized vortices with a vorticity is found to
be expressed by a simple equation, which reflects the chirality of the Cooper
pairing. Hence, the observation of the particle density depletion and the
measurement of the angular momentum will provide the information on the
core-bound state and -wave superfluidity. Moreover, the details on the zero
energy Majorana state are discussed in the vicinity of the BCS-to-BEC
evolution. It is demonstrated numerically that the zero energy Majorana state
appears in the weak coupling BCS limit only when the vortex winding number is
odd. There exist the branches of the core bound states for a vortex
state with vorticity , whereas only one of them can be the zero energy.
This zero energy state vanishes at the BCS-BEC topological phase transition,
because of interference between the core-bound and edge-bound states.Comment: 15 pages, 9 figures, published versio
Spin textures in condensates with large dipole moments
We have solved numerically the ground states of a Bose-Einstein condensate in
the presence of dipolar interparticle forces using a semiclassical approach.
Our motivation is to model, in particular, the spontaneous spin textures
emerging in quantum gases with large dipole moments, such as 52Cr or Dy
condensates, or ultracold gases consisting of polar molecules. For a
pancake-shaped harmonic (optical) potential, we present the ground state phase
diagram spanned by the strength of the nonlinear coupling and dipolar
interactions. In an elongated harmonic potential, we observe a novel helical
spin texture. The textures calculated according to the semiclassical model in
the absence of external polarizing fields are predominantly analogous to
previously reported results for a ferromagnetic F = 1 spinor Bose-Einstein
condensate, suggesting that the spin textures arising from the dipolar forces
are largely independent of the value of the quantum number F or the origin of
the dipolar interactions.Comment: 9 pages, 6 figure
Generic Phase Diagram of Fermion Superfluids with Population Imbalance
It is shown by microscopic calculations for trapped imbalanced Fermi
superfluids that the gap function has always sign changes, i.e., the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state like, up to a critical imbalance
, beyond which normal state becomes stable, at temperature T=0. A phase
diagram is constructed in vs , where the BCS state without sign change
is stable only at . We reproduce the observed bimodality in the
density profile to identify its origin and evaluate as functions of
and the coupling strength. These dependencies match with the recent
experiments.Comment: 5 pages, 5 figures, replaced by the version to appear in PR
Direct Imaging of Spatially Modulated Superfluid Phases in Atomic Fermion Systems
It is proposed that the spatially modulated superfluid phase, or the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state could be observed in resonant
Fermion atomic condensates which are realized recently. We examine optimal
experimental setups to achieve it by solving Bogoliubov-de Gennes equation both
for idealized one-dimensional and realistic three-dimensional cases. The
spontaneous modulation of this superfluid is shown to be directly imaged as the
density profiles either by optical absorption or by Stern-Gerlach experiments.Comment: 4 pages, 3 figure
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