1,721,020 research outputs found
Constants of motion in the dynamics of a 2N-junction SQUID
No full textWe show that a 2N-junction SQUID (superconducting quantum interference device) made of 2N overdamped, shunted, identical junctions may be described as a system having only six degrees of freedom for any N ≥ 3. This is achieved by means of the reduction introduced by Watanabe and Strogatz [Physica D 74 (1994) 197] for series biased arrays. In our case six rather than three degrees of freedom are necessary to describe the system, due to the requirement of phase quantization along the superconducting loop constituting the device. Generalization to multijunction parallel arrays is straightforward
Phase locking of fluxons oscillations in Long Josephson Junctions with surface losses
No full textThe influence of surface-resistance dissipation on phase locking of fluxon oscillations in long Josephson junctions of in-line geometry subjected to microwave fields which interact with the fluxon at the junction boundaries is studied by the perturbation- theory map approach and by full integration of the pde model of the junction
Domain walls and bubble droplets in immiscible binary Bose gases
No full textThe existence and stability of domain walls (DWs) and bubble-droplet (BD) states in binary mixtures of
quasi-one-dimensional ultracold Bose gases with inter- and intraspecies repulsive interactions is considered.
Previously, DWs were studied by means of coupled systems of Gross-Pitaevskii equations (GPEs) with cubic
terms, which model immiscible binary Bose-Einstein condensates (BECs). We address immiscible BECs with
two- and three-body repulsive interactions, as well as binary Tonks–Girardeau (TG) gases, using systems of
GPEs with cubic and quintic nonlinearities for the binary BEC, and coupled nonlinear Schr ̈odinger equations
with quintic terms for the TG gases. Exact DW solutions are found for the symmetric BEC mixture, with equal
intraspecies scattering lengths. Stable asymmetric DWs in the BEC mixtures with dissimilar interactions in the
two components, as well as of symmetric and asymmetric DWs in the binary TG gas, are found by means of
numerical and approximate analytical methods. In the BEC system, DWs can be easily put in motion by phase
imprinting. Combining a DW and anti-DW on a ring, we construct BD states for both the BEC and TG models.
These consist of a dark soliton in one component (the “bubble”), and a bright soliton (the “droplet”) in the other.
In the BEC system, these composite states are mobile, too
Escape time characterization of pendular Fabry-Perot
No full textIn a pendular Fabry-Perot interferometer the system placed inside one of the minimum of the optomechanical potential undergoes an escape if it crosses the point of sudden change of reflectivity near the top of the potential well. We demonstrate that the loss of information that occurs retaining only the sequence of escapes, rather than the full trajectory, is mild if suitable signal processing techniques are applied to reveal the noise intensity or the presence of a coherent signal
Mutual inductance effects in rf driven planar Josephson junctions arrays
No full textPACS. 85.25.Am Superconducting device, characterization, design, and modeling[:AND:] 85.25.Dq Superconducting logic elements and memory devices,
Double parametric resonance for matter-wave solitons in a time-modulated trap
No full textWe analyze the motion of solitons in a self-attractive Bose-Einstein condensate, loaded into a quasi-onedimensional
parabolic potential trap, which is subjected to time-periodic modulation with an amplitude « and
frequency V. First, we apply the variational approximation, which gives rise to decoupled equations of motion
for the center-of-mass coordinate of the soliton, jstd, and its width astd. The equation for jstd is the ordinary
Mathieu equation sMEd sit is an exact equation that does not depend on the adopted ansatzd, the equation for
astd being a nonlinear generalization of the ME. Both equations give rise to the same map of instability zones
in the s«,Vd plane, generated by the parametric resonances sPRsd, if the instability is defined as the onset of
growth of the amplitude of the parametrically driven oscillations. In this sense, the double PR is predicted.
Direct simulations of the underlying Gross-Pitaevskii equation give rise to a qualitatively similar but quantitatively
different stability map for oscillations of the soliton’s width astd. In the direct simulations, we identify
the soliton dynamics as unstable if the instability sagain, realized as indefinite growth of the amplitude of
oscillationsd can be detected during a time comparable with, or smaller than, the lifetime of the condensate
stherefore accessible to experimental detectiond. Two-soliton configurations are also investigated. It is concluded
that multiple collisions between solitons are elastic, and they do not affect the instability borders
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