121,269 research outputs found
Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential
We study vortex formation in a Bose-Einstein condensate in a rotating
double-well potential. Besides the ordinary quantized vortices and elusive
ghost vortices, "hidden" vortices are found distributing along the central
barrier. These hidden vortices are invisible like ghost vortex but carry
angular momentum. Moreover, their core size is not given by the healing length,
but is strongly influenced by the external potential. We find that the
Feynman's rule can be well satisfied only after including the hidden vortices.
There is no critical rotating frequency for the formation of hidden vortex
while there is one for the formation of ordinary visible vortices. Hidden
vortices can be revealed in the free expansion of the Bose-Einstein
condensates. In addition, the hidden vortices in a Bose-Einstein condensate can
appear in other external potentials, such as a rotating anisotropic toroidal
trap.Comment: 6pages,5figure
Point vortices on the sphere: a case with opposite vorticities
We study systems formed of 2N point vortices on a sphere with N vortices of
strength +1 and N vortices of strength -1. In this case, the Hamiltonian is
conserved by the symmetry which exchanges the positive vortices with the
negative vortices. We prove the existence of some fixed and relative
equilibria, and then study their stability with the ``Energy Momentum Method''.
Most of the results obtained are nonlinear stability results. To end, some
bifurcations are described.Comment: 35 pages, 9 figure
Dynamics of Non-Abelian Vortices
The scattering is studied using moduli space metric for well-separated
vortices of non-Abelian vortices in (2+1)-dimensional U(N) gauge theories with
N Higgs fields in the fundamental representation. Unlike vortices in the
Abelian-Higgs model, dynamics of non-Abelian vortices has a lot of new
features; The kinetic energy in real space can be transfered to that of
internal orientational moduli and vice versa, the energy and charge transfer
between two vortices, the scattering angle of collisions with a fixed impact
parameter depends on the internal orientations, and some resonances appear due
to synchronization of the orientations. Scattering of dyonic non-Abelian
vortices in a mass deformed theory is also studied. We find a bound state of
two vortices moving along coils around a circle, like a loop of a phone code.Comment: 45 pages, 13 figure
Dissociation Transition of a Composite Lattice of Magnetic Vortices in the Flux-Flow Regime of Two-Band Superconductors
In multiband superconductors, each superconducting condensate supports
vortices with fractional quantum flux. In the ground state, vortices in
different bands are spatially bounded together to form a composite vortex,
carrying one quantum flux \Phi_0. Here we predict dissociation of the composite
vortices lattice in the flux flow state due to the disparity of the vortex
viscosity and flux of the vortex in different bands. For a small driving
current, composite vortices start to deform, but the constituting vortices in
different bands move with the same velocity. For a large current, composite
vortices dissociate and vortices in different bands move with different
velocities. The dissociation transition shows up as an increase of flux flow
resistivity. In the dissociated phase, Shapiro steps are developed when an ac
current is superimposed with a dc current.Comment: 4.5 pages, 3 figure
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