17,835 research outputs found
Pulses and Snakes in Ginzburg--Landau Equation
Using a variational formulation for partial differential equations (PDEs)
combined with numerical simulations on ordinary differential equations (ODEs),
we find two categories (pulses and snakes) of dissipative solitons, and analyze
the dependence of both their shape and stability on the physical parameters of
the cubic-quintic Ginzburg-Landau equation (CGLE). In contrast to the regular
solitary waves investigated in numerous integrable and non-integrable systems
over the last three decades, these dissipative solitons are not stationary in
time. Rather, they are spatially confined pulse-type structures whose envelopes
exhibit complicated temporal dynamics. Numerical simulations reveal very
interesting bifurcations sequences as the parameters of the CGLE are varied.
Our predictions on the variation of the soliton amplitude, width, position,
speed and phase of the solutions using the variational formulation agree with
simulation results.Comment: 30 pages, 14 figure
On the feasibility of studying vortex noise in 2D superconductors with cold atoms
We investigate the feasibility of using ultracold neutral atoms trapped near
a thin superconductor to study vortex noise close to the
Kosterlitz-Thouless-Berezinskii transition temperature. Alkali atoms such as
rubidium probe the magnetic field produced by the vortices. We show that the
relaxation time of the Zeeman sublevel populations can be conveniently
adjusted to provide long observation times. We also show that the transverse
relaxation times for Zeeman coherences are ideal for studying the vortex
noise. We briefly consider the motion of atom clouds held close to the surface
as a method for monitoring the vortex motion.Comment: 4 pages, 1 figur
Pairing, Ferromagnetism, and Condensation of a normal spin-1 Bose gas
We theoretically study the stability of a normal, spin disordered, homogenous
spin-1 Bose gas against ferromagnetism, pairing, and condensation through a
Random Phase Approximation which includes exchange (RPA-X). Repulsive
spin-independent interactions stabilize the normal state against both
ferromagnetism and pairing, and for typical interaction strengths leads to a
direct transition from an unordered normal state to a fully ordered single
particle condensate. Atoms with much larger spin-dependent interaction may
experience a transition to a ferromagnetic normal state or a paired superfluid,
but, within the RPA-X, there is no instability towards a normal state with
spontaneous nematic order. We analyze the role of the quadratic Zeeman effect
and finite system size.Comment: 4 pages, 3 figures, 1 table. Supplementary materials attache
Quantum electrodynamics for vector mesons
Quantum electrodynamics for mesons is considered. It is shown that, at
tree level, the value of the gyromagnetic ratio of the is fixed to 2
in a self-consistent effective quantum field theory. Further, the mixing
parameter of the photon and the neutral vector meson is equal to the ratio of
electromagnetic and strong couplings, leading to the mass difference
at tree order.Comment: 4 pages, 2 figures, REVTeX 4, accepted for publication in PR
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