Pseudo-regular oscillations induced by external noise

An examination of the effect of noise on a general system at a saddle-node bifurcation has revealed that, in the limit of weak noise, the probability density of the time to pass through the saddle-node has a universal shape, the specific kinetics of the particular system serving only to set the time scale. This probability density is displayed and its salient features are explicated. In the case of a saddle-node bifurcation leading to relaxation oscillations, this analysis leads to the prediction of the existence of noise-induced oscillations which appear much less random than might at first be expected. The period of these oscillations has a well-defined, nonzero most probable value, the inverse of which is a noise-induced frequency. This frequency can be detected as a peak in power spectra from numerical simulations of such a system. This is the first case of the prediction and detection of a noise-induced frequency of which the authors are aware.     

Dynamical instability induced by the zero mode under symmetry breaking external perturbation

A complex eigenvalue in the Bogoliubov–de Gennes equations for a stationary Bose–Einstein condensate in the ultracold atomic system indicates the dynamical instability of the system. We also have the modes with zero eigenvalues for the condensate, called the zero modes, which originate from the spontaneous breakdown of symmetries. Although the zero modes are suppressed in many theoretical analyses, we take account of them in this paper and argue that a zero mode can change into one with a pure imaginary eigenvalue by applying a symmetry breaking external perturbation potential. This emergence of a pure imaginary mode adds a new type of scenario of dynamical instability to that characterized by the complex eigenvalue of the usual excitation modes. For illustration, we deal with two one-dimensional homogeneous Bose–Einstein condensate systems with a single dark soliton under a respective perturbation potential, breaking the invariance under translation, to derive pure imaginary modes.     

Further evidence of a phase transition induced by external noise

Transitions in a biochemical model with multiple (one or three) steady states can be a genuine consequence of external noise, in agreement with an earlier finding by Horsthemke and Lefever.     

A microscopic model for noise induced transport: Heat-bath nonlinearly driven by external white noise

This work explores the observation that, even in the absence of a net externally applied bias, a symmetric homogeneous system coupled linearly to two heat baths is capable of producing unidirectional motion simply by nonlinearly driving one of the heat baths by an external Gaussian white noise. This is quite contrary to the traditional observation that, in order to obtain a net drift current, a state-dependent dissipation, which is a consequence of nonlinear system-bath coupling, is ubiquitous.     

Noise induced transitions due to external additive noise

The stationary Fokker-Planck equation in the two-dimensional case is solved locally using an antisymmetric tensor which transforms the problem into the potential case. Several examples are discussed which show that even additive external noise influences the extremal behaviour of the stochastic potential.     

Phase textures induced by dc-current pair breaking in weakly coupled multilayer structures and two-gap superconductors

We predict the current-induced formation of equilibrium phase textures for a multicomponent superconducting order parameter. Using the two-component Ginzburg-Landau and Usadel equations, we show that, for weakly coupled comoving superconducting condensates, the dc current I first causes the breakdown of the phase-locked state at I>I{c1} followed by the formation of intrinsic phase textures well below the depairing current I{d}. These phase textures can manifest themselves in multilayer structures, atomic Bose condensate mixtures in optical lattices, and two-gap superconductors, particularly MgB(2), where they can result in oscillating and resistive switching effects.     

Ergodicity breaking and parametric resonances in systems with long-range interactions

We explore the mechanism responsible for the ergodicity breaking in systems with long-range forces. In thermodynamic limit such systems do not evolve to the Boltzmann-Gibbs equilibrium, but become trapped in an out-of-equilibrium quasi-stationary-state. Nevertheless, we show that if the initial distribution satisfies a specific constraint-a generalized virial condition-the quasistationary state is very close to ergodic and can be described by Lynden-Bell statistics. On the other hand, if the generalized virial condition is violated, parametric resonances are excited, leading to chaos and ergodicity breaking.     

A perturbation expansion for external wide band Markovian noise: Application to transitions induced by Ornstein-Uhlenbeck noise

A method is presented which permits to calculate the stationary probability density of non equilibrium systems subjected to wide band external colored noise. It consists of a systematic perturbation expansion in terms of the correlation time of the noise. The method is presented in detail for noise of the Ornstein-Uhlenbeck type. It is used to illustrate the effect of correlations on two examples of noise induced transitions.     

Symmetry breaking of fluctuation dynamics by noise color

Activated escape is investigated for systems that are driven by noise whose power spectrum peaks at a finite frequency. Analytic theory and analog and digital experiments show that the system dynamics during escape exhibit a symmetry-breaking transition as the width of the fluctuational spectral peak is varied. For double-well potentials, even a small asymmetry may result in a parametrically large difference of the activation energies for escape from different wells.     

Telegraph noise in coupled quantum dot circuits induced by a quantum point contact

Charge detection utilizing a highly biased quantum point contact has become the most effective probe for studying few electron quantum dot circuits. Measurements on double and triple quantum dot circuits is performed to clarify a back action role of charge sensing on the confined electrons. The quantum point contact triggers inelastic transitions, which occur quite generally. Under specific device and measurement conditions these transitions manifest themselves as bounded regimes of telegraph noise within a stability diagram. A nonequilibrium transition from artificial atomic to molecular behavior is identified. Consequences for quantum information applications are discussed.     

The entanglement of two dipole-dipole coupled atoms induced by nondegenerate two-mode thermal noise

We investigate the entanglement properties of a system of two dipole-dipole coupled two-level atoms resonantly interacting with a two-mode thermal field in a high-Q cavity. We obtain the evolution operator for this system in an analytical form, and use it to evaluate the atom-atom entanglement through the calculation of the negativity. The results show that the atom-atom entanglement is dependent on cavity field intensity and dipole interaction strength. We find that the dipole interaction can produce a considerable amount of entanglement between the two atoms. Original Text ? Astro, Ltd., 2009. The article is published in the original.     

Ergodicity in computer simulation of quantum dissipative processes

The ergodicity principle in quantum theory is employed for elaboration of a new quantum trajectory technique which is used for numerical simulation of quantum dissipative systems. With this purpose the density matrix of a quantum system is represented as a sum over an ensemble of quantum states in time intervals. The method is employed for computations of a quantum anharmonic oscillator.     

Application of extraction induced by emulsion breaking for trace multi-element determination in jet fuel by inductively coupled plasma-mass spectrometry

ABSTRACT

A novel method, based on extraction induced by emulsion breaking, is proposed for rapid simultaneous determination of iron, manganese, copper, and zinc in jet fuel by inductively coupled plasma-mass spectrometry. Several parameters affecting the extraction efficiency were investigated including the concentrations of nitric acid and emulsifying agents, centrifugal speed, and extraction time. The limits of detection for iron, manganese, copper, and zinc were 0.116, 0.028, 0.06, and 0.085 µg L^?1, respectively. The accuracy of the method was tested by the analysis of spiked samples (recovery percentages between 90% and 107% were observed) and by comparison with a well-established method.     

Angular symmetry breaking induced by electromagnetic field

It is well known that velocities do not commute in the presence of an electromagnetic field. This property implies that angular algebra symmetries, such as the sO(3) and Lorentz algebra symmetries, are broken. To restore these angular symmetries we show the necessity of adding the Poincaré momentum M to the simple angular momentum L. These restorations performed successively in a flat space and in a curved space lead in each case to the generation of a Dirac magnetic monopole. In the particular case of the Lorentz algebra we consider an application of our theory to gravitoelectromagnetism. In this last case we establish a qualitative relation giving the mass spectrum for dyons.     

Spontaneous supersymmetry breaking induced by vacuum condensates

We propose a novel mechanism of spontaneous supersymmetry breaking which relies upon a ubiquitous feature of Quantum Field Theory, vacuum condensates. Such condensates play a crucial role in many phenomena. Examples include Unruh effect, superconductors, particle mixing, and quantum dissipative systems. We argue that in all these phenomena supersymmetry, when present, is spontaneously broken. Evidence for our conjecture is given for the Wess–Zumino model, that can be considered as an approximation to the supersymmetric extensions of the above mentioned systems. The magnitude of the effect is estimated for a recently proposed experimental setup based on an optical lattice.     

Electroweak symmetry breaking induced by dark matter

The mechanism behind electroweak symmetry breaking (EWSB) and the nature of dark matter (DM) are currently among the most important issues in high energy physics. Since a natural dark matter candidate is a weakly interacting massive particle or WIMP, with mass around the electroweak scale, it is clearly of interest to investigate the possibility that DM and EWSB are closely related. In the context of a very simple extension of the Standard Model, the inert doublet model, we show that dark matter could play a crucial role in the breaking of the electroweak symmetry. In this model, dark matter is the lightest component of an inert scalar doublet. The coupling of the latter with the Standard Model Higgs doublet breaks the electroweak symmetry at one-loop, à la Coleman–Weinberg. The abundance of dark matter, the breaking of the electroweak symmetry and the constraints from electroweak precision measurements can all be accommodated by imposing (an exact or approximate) custodial symmetry.     

Nonequilibrium transitions driven by external dichotomous noise

The stationary probability densityP _s for a class of nonlinear one-dimensional models driven by a dichotomous Markovian process (DMP)I _t , can be calculated explicitly. For the specific case of the Stratonovich model, x=ax –-x ³ +I _t x, the qualitative shape ofP _s and its support is discussed in the whole parameter region. The location of the maxima ofP _s shows a behavior similar to order parameters in continuous phase transitions. The possibility of a noiseinduced change from continuous to a discontinuous transition in an extended model, in which the DMP couples also to the cubic term, is discussed. The time-dependent moments x_t ⁿ can be represented as an infinite series of terms, which are determined by a recursion formula. For negative even moments the series terminates and the long-time behavior can be obtained analytically. As a function of the physical parameters, qualitative changes of this behavior may occur which can be partially related to the behavior ofP _s . All results reproduce those for Gaussian white noise in the corresponding limit. The influence of the finite correlation time and the discreteness of the space of states of the DMP are discussed. An extensive list of references is contained in U. Behn, K. Schiele, and A. Teubel,Wiss. Z. Karl-Marx-Univ. Leipzig, Mathem.-Naturwiss. R. 34:602 (1985).Contribution to the symposium on the Statistical Mechanics of Phase Transitions —Mathematical and Physical Aspects, Tebo, Czechoslovakia, September 1–6, 1986.     

Structure changes induced by external multiplicative noise in the electrohydrodynamic instability of nematic liquid crystals

We study the influence of external multiplicative noise on the electrohydrodynamic instability (EHD) in nematic liquid crystals. It turns out that the correlation time _n and the intensityQ of the noise are the crucial parameters to control the system. Different types of noise lead to minor quantitative changes when compared to Gaussian white noise, leaving the qualitative aspects unchanged. With increasing noise intensity the threshold for the onset of the first instability changes drastically. We observe that the curvature arising when the threshold of the various instabilities is plotted as a function of the noise intensity changes as one is going, e.g., from the onset of Williams domains (WD) to the onset of the grid pattern (GP). This result reflects the transition in the flow structure from two-dimensional (WD) to three-dimensional (GP, DSM) flow patterns. As the intensity of the noise is increased further, the onset of the first instability becomes more complex. The measurement of the nonlinear onset time shows a strong dependence on the noise intensityQ, which is linear for WD and GP well above onset. The linear onset time shows an unexpected dependence on the noise intensity close to the onset of the first instability. For sufficiently long correlation times of the noise, a destabilization by noise is obtained.     

Current rectification by spontaneous symmetry breaking in coupled nanomechanical shuttles

We investigate the transport and the dynamical properties of tunnel-coupled double charge shuttles. The oscillation frequencies of two shuttles are mode locked to integer multiples of the applied voltage frequency omega. We show that left-right-symmetric double shuttles may generate direct net current due to bistable motions caused by parametric instability. The symmetry-broken direct current appears near omega = Omega0/(2j-1), (j = 1,2,...), where Omega0 is the dressed resonance frequency of the relative motion of the two shuttles.