Search results for "Stability"
showing 10 items of 3085 documents
Jet dynamics and stability
2013
The dynamics and stability of extragalactic jets may be strongly influenced by small (and probable) di_erences in pressure between the jet and the ambient and within the jet itself. The former give rise to expansion and recollimation of the jet. This occurs in the form of conical shocks, or Mach disks, if the pressure di_erence is large enough. Pressure asymmetries within the jet may trigger the development of helical patterns via coupling to kink current-driven instability, or to helical Kelvin-Helmholtz instability, depending on the physical conditions in the jet. I summarize here the evidence collected during the last years on the presence of recollimation shocks and waves in jets. In th…
Noise-induced effects in nonlinear relaxation of condensed matter systems
2015
Abstract Noise-induced phenomena characterise the nonlinear relaxation of nonequilibrium physical systems towards equilibrium states. Often, this relaxation process proceeds through metastable states and the noise can give rise to resonant phenomena with an enhancement of lifetime of these states or some coherent state of the condensed matter system considered. In this paper three noise induced phenomena, namely the noise enhanced stability, the stochastic resonant activation and the noise-induced coherence of electron spin, are reviewed in the nonlinear relaxation dynamics of three different systems of condensed matter: (i) a long-overlap Josephson junction (JJ) subject to thermal fluctuat…
Non-Gaussian noise effects in the dynamics of a short overdamped Josephson junction
2010
The role of thermal and non-Gaussian noise on the dynamics of driven short overdamped Josephson junctions is studied. The mean escape time of the junction is investigated considering Gaussian, Cauchy-Lorentz and Levy-Smirnov probability distributions of the noise signals. In these conditions we find resonant activation and the first evidence of noise enhanced stability in a metastable system in the presence of Levy noise. For Cauchy-Lorentz noise source, trapping phenomena and power law dependence on the noise intensity are observed.
RESONANT ACTIVATION AND NOISE ENHANCED STABILITY IN JOSEPHSON JUNCTIONS
2005
We investigate the interplay of two noise-induced effects on the temporal characteristics of short overdamped Josephson junctions in the presence of a periodic driving. We find that: (i) the mean life time of superconductive state has a minimum as a function of driving frequency, and near the minimum it actually does not depend on the noise intensity (resonant activation phenomenon); (ii) the noise enhanced stability phenomenon increases the switching time from superconductive to the resistive state. As a consequence there is a suitable frequency range of clock pulses, at which the noise has a minimal effect on pulse propagation in RSFQ electronic devices.
EFFECTS OF COLORED NOISE IN SHORT OVERDAMPED JOSEPHSON JUNCTION
2008
We investigate the transient dynamics of a short overdamped Josephson junction with a periodic driving signal in the presence of colored noise. We analyze noise induced henomena, specifically resonant activation and noise enhanced stability. We find that the positions both of the minimum of RA and maximum of NES depend on the value of the noise correlation time tau_c. Moreover, in the range where RA is observed, we find a non-monotonic behavior of the mean switching time as a function of the correlation time tau_c.
Incoherent modulation instability in instantaneous nonlinear Kerr media
2005
We demonstrate theoretically and experimentally in an optical fiber system that partially temporally incoherent light exhibits modulational instability during its propagation in an instantaneous response nonlinear medium. We show that the modulation frequency and gain are substantially increased with respect to the corresponding values of coherent modulational instability.
Numerical simulation of Kerr nonlinear systems : analyzing non-classical dynamics
2019
Abstract We simulate coherent driven free dissipative Kerr nonlinear system numerically using Euler’s method by solving Heisenberg equation of motion and time evolving block decimation (TEBD) algorithm, and demonstrate how the numerical results are analogous to classical bistability. The comparison with analytics show that the TEBD numerics follow the quantum mechanical exact solution obtained by mapping the equation of motion of the density matrix of the system to a Fokker-Plank equation . Comparing between two different numerical techniques, we see that the semi-classical Euler’s method gives the dynamics of the system field of one among two coherent branches, whereas TEBD numerics genera…
Light-Induced Excited Spin State Trapping in Iron(II) Complexes
1987
In the course of our studies on the thermally induced high spin (HS) ↔ low spin (LS) transition in iron(II) complexes /1/, \({\!^5{\text{T}}_2}_{\text{g}}\) ↔ \({\!^1{\text{A}}_1}_{\text{g}}\) in the approximation of Oh symmetry, we have observed in 1984 a new photophysical effect /2/: If, at sufficiently low temperature, the solid spin crossover complex is irradiated with green light into the \({\!^1{\text{A}}_1}\)→ \({\!^1{\text{T}}_1}\) ligand field absorption band, the thermodynamically stable LS state can be converted to the metastable HS state and trapped with practically infinite lifetime. We have called this unusual phenomenon “Light-Induced Excited Spin State Trapping (LIESST)”.
Balitsky-Kovchegov equation at next-to-leading order accuracy with a resummation of large logarithms
2016
We include resummation of large transverse logarithms into the next-to-leading order Balitsky-Kovchegov equation. The resummed NLO evolution equation is shown to be stable, the evolution speed being significantly reduced by higher order corrections. The contributions from $\alpha_s^2$ terms that are not enhanced by large logarithms are found to be numerically important close to phenomenologically relevant initial conditions.
Stabilizing and increasing the magnetic moment of half-metals: The role of Li in half-HeuslerLiMnZ(Z=N,P,Si)
2015
Due to their similarities to metastable zinc-blende half-metals, we systematically examined the half-Heusler compounds $\ensuremath{\beta}\text{-LiMn}Z$ ($Z=\text{N},\text{P}$ and Si) for their electronic, magnetic, and stability properties at optimized lattice constants and strained lattice constants that exhibit half-metallic properties. We also report the other phases of the half-Heusler structure ($\ensuremath{\alpha}$ and $\ensuremath{\gamma}$ phases), but they are unlikely to be grown. The magnetic moments of these stable Li-based compounds are expected to reach as high as $4{\ensuremath{\mu}}_{\mathrm{B}}$ per unit cell when $Z=\text{Si}$ and $5{\ensuremath{\mu}}_{\mathrm{B}}$ per un…