46 research outputs found
Synchrony breakdown and noise-induced oscillation death in ensembles of serially connected spin-torque oscillators
We consider collective dynamics in the ensemble of serially connected
spin-torque oscillators governed by the Landau-Lifshitz-Gilbert-Slonczewski
magnetization equation. Proximity to homoclinicity hampers synchronization of
spin-torque oscillators: when the synchronous ensemble experiences the
homoclinic bifurcation, the Floquet multiplier, responsible for the temporal
evolution of small deviations from the ensemble mean, diverges. Depending on
the configuration of the contour, sufficiently strong common noise, exemplified
by stochastic oscillations of the current through the circuit, may suppress
precession of the magnetic field for all oscillators. We derive the explicit
expression for the threshold amplitude of noise, enabling this suppression.Comment: 12 pages, 13 figure
Steady Stokes flow with long-range correlations, fractal Fourier spectrum, and anomalous transport
We consider viscous two-dimensional steady flows of incompressible fluids
past doubly periodic arrays of solid obstacles. In a class of such flows, the
autocorrelations for the Lagrangian observables decay in accordance with the
power law, and the Fourier spectrum is neither discrete nor absolutely
continuous. We demonstrate that spreading of the droplet of tracers in such
flows is anomalously fast. Since the flow is equivalent to the integrable
Hamiltonian system with 1 degree of freedom, this provides an example of
integrable dynamics with long-range correlations, fractal power spectrum, and
anomalous transport properties.Comment: 4 pages, 4 figures, published in Physical Review Letter