Intermittencies in complex Ginzburg-Landau equation by varying system size

Dynamical behaviour of the one-dimensional complex Ginzburg--Landau equation (CGLE) with finite system size $L$ is investigated, based on numerical simulations. By varying the system size and keeping other system parameters in the defect turbulence region (defect turbulence in large $L$ limit), a number of intermittencies new for the CGLE system are observed in the processes of pattern formations and transitions while the system dynamics varies from a homogeneous periodic oscillation to strong defect turbulence.     

Complex Ginzburg-Landau equation for nonlinear travelling waves in extrinsic semiconductors

We study the nonlinear state of a travelling-wave instability occurring close to the onset of impact ionization in extrinsic semiconductors. Our investigations are based on a complex Ginzburg-Landau equation (CGLE). For a simple generation-recombination function including impact ionization and thermal recombination of the charge carriers, we find a supercritical bifurcation of stable travelling waves for most parameter values. The results are compared with a numerical solution of the basic equations of motion. Furthermore, we expect that weak turbulence phenomena should be observed in semiconductors if their specific generation-recombination kinetics leads to a CGLE with appropriate coefficients.     

Shallow water rogue wavetrains in nonlinear optical fibers

In addition to deep-water rogue waves which develop from the modulation instability of an optical CW, wave propagation in optical fibers may also produce shallow water rogue waves. These extreme wave events are generated in the modulationally stable normal dispersion regime. A suitable phase or frequency modulation of a CW laser leads to chirp-free and flat-top pulses or flaticons which exhibit a stable self-similar evolution. Upon collision, flaticons at different carrier frequencies, which may also occur in wavelength division multiplexed transmission systems, merge into a single, high-intensity, temporally and spatially localized rogue pulse.     

Bifurcation to fully nonlinear synchronized structures in slowly varying media

The selection of fully nonlinear extended oscillating states is analyzed in the context of one-dimensional nonlinear evolution equations with slowly spatially varying coefficients on a doubly infinite domain. Two types of synchronized structures referred to as steep and soft global modes are shown to exist. Steep global modes are characterized by the presence of a sharp stationary front at a marginally absolutely unstable station and their frequency is determined by the corresponding linear absolute frequency, as in Dee–Langer propagating fronts. Soft global modes exhibit slowly varying amplitude and wave number over the entire domain and their frequency is determined by the application of a saddle point condition to the local nonlinear dispersion relation. The two selection criteria are compared and shown to be mutually exclusive. The onset of global instability first gives rise to a steep global mode via a saddle-node bifurcation as soon as local linear absolute instability is reached somewhere in the medium. As a result, such self-sustained structures may be observed while the medium is still globally stable in a strictly linear approximation. Soft global modes only occur further above global onset and for sufficiently weak advection. The entire bifurcation scenario and state diagram are described in terms of three characteristic control parameters. The complete spatial structure of nonlinear global modes is analytically obtained in the framework of WKBJ approximations.     

Symmetry-breaking solutions of the Ginzburg-Landau equation

We consider the question of the existence of nonradial solutions of the Ginzburg-Landau equation. We present results indicating that such solutions exist. We seek such solutions as saddle points of the renormalized Ginzburg-Landau free-energy functional. There are two main points in our analysis: searching for solutions that have certain point symmetries and characterizing saddle-point solutions in terms of critical points of certain intervortex energy function. The latter critical points correspond to forceless vortex configurations.     

Periodic solutions of the Ginzburg-Landau equation

Spatially periodic solutions to the Ginzburg-Landau equation are considered. In particular we obtain: criteria for primary and secondary bifurcation; limit cycle solutions; nonlinear dispersion relations relating spatial and temporal frequencies. Only relatively simple tools appear in the treatment and as a result a wide range of parameter cases are considered. Finally we briefly treat the case of spatial bifurcations.     

Renormalization Group and the Ginzburg-Landau equation

We use Renormalization Group methods to prove detailed long time asymptotics for the solutions of the Ginzburg-Landau equations with initial data approaching, asx±, different spiraling stationary solutions. A universal pattern is formed, depending only on this asymptotics at spatial infinity.Supported by NSF grant DMS-8903041 and by EEC Grant SCI-CT91-0695TSTS     

Front solutions for the Ginzburg-Landau equation

We prove the existence of front solutions for the Ginzburg-Landau equation $$\partial _t u(x,t) = \partial _x^2 u(x,t) + (1 - |u(x,t)|^2 )u(x,t)$$ , interpolating between two stationary solutions of the form \(u(x) = \sqrt {1 - q^2 } e^{iqx}\) with different values ofq atx=±∞. Such fronts are shown to exist when at least one of theq is in the Eckhaus-unstable domain.     

Stability of moving fronts in the Ginzburg-Landau equation

We use Renormalization Group ideas to study stability of moving fronts in the Ginzburg-Landau equation in one spatial dimension. In particular, we prove stability of the real fronts under complex perturbations. This extends the results of Aronson and Weinberger to situations where the maximum principle is inapplicable and constitutes a step in proving the general marginal stability hypothesis for the Ginzburg-Landau equation.Supported by EC grant SC1-CT91-0695Supported by NSF grant DMS-8903041     

Bistability in the complex Ginzburg-Landau equation with drift

Properties of the complex Ginzburg-Landau equation with drift are studied focusing on the Benjamin-Feir stable regime. On a finite interval with Neumann boundary conditions the equation exhibits bistability between a spatially uniform time-periodic state and a variety of nonuniform states with complex time dependence. The origin of this behavior is identified and contrasted with the bistable behavior present with periodic boundary conditions and no drift.     

On the invariants of the complex Ginzburg-Landau equation

Using Lie group theory, both the invariants and the similarity variables of the complex Ginzburg—Landau equation V_xx = a(V_t + bV) + cV|V|^2kwherea,b,c?Iandk?I are constructed.     

Twisted vortex filaments in the three-dimensional complex Ginzburg-Landau equation

The structure and dynamics of vortex filaments that form the cores of scroll waves in three-dimensional oscillatory media described by the complex Ginzburg-Landau equation are investigated. The study focuses on the role that twist plays in determining the bifurcation structure in various regions of the (alpha,beta) parameter space of this equation. As the degree of twist increases, initially straight filaments first undergo a Hopf bifurcation to helical filaments; further increase in the twist leads to a secondary Hopf bifurcation that results in supercoiled helices. In addition, localized states composed of superhelical segments interspersed with helical segments are found. If the twist is zero, zigzag filaments are found in certain regions of the parameter space. In very large systems disordered states comprising zigzag and helical segments with positive and negative senses exist. The behavior of vortex filaments in different regions of the parameter space is explored in some detail. In particular, an instability for nonzero twist near the alpha=beta line suggests the existence of a nonsaturating state that reduces the stability domain of straight filaments. The results are obtained through extensive simulations of the complex Ginzburg-Landau equation on large domains for long times, in conjunction with simulations on equivalent two-dimensional reductions of this equation and analytical considerations based on topological concepts.     

Convective and absolute instabilities in the subcritical Ginzburg-Landau equation

We study the nature of the instability of the homogeneous steady states of the subcritical real Ginzburg-Landau equation in the presence of group velocity. The shift of the absolute instability threshold of the trivial steady state, induced by the destabilizing cubic nonlinearities, is confirmed by the numerical analysis of the evolution of its perturbations. It is also shown that the dynamics of these perturbations is such that finite size effects may suppress the transition from convective to absolute instability. Finally, we analyze the instability of the subcritical middle branch of steady states, and show, analytically and numerically, that this branch may be convectively unstable for sufficiently high values of the group velocity. Received 17 December 1998     

Motion of spiral waves in the complex Ginzburg-Landau equation

Solutions of the general cubic complex Ginzburg-Landau equation comprising multiple spiral waves are considered. For parameters close to the vortex limit, and for a system of spiral waves with well-separated centres, laws of motion of the centres are found which vary depending on the order of magnitude of the separation of the centres. In particular, the direction of the interaction changes from along the line of centres to perpendicular to the line of centres as the separation increases, with the strength of the interaction algebraic at small separations and exponentially small at large separations. The corresponding asymptotic wavenumber and frequency are determined. These depend on the positions of the centres of the spirals, and so evolve slowly as the spirals move.     

Noise-induced synchronization of spatiotemporal chaos in the Ginzburg-Landau equation

We have studied noise-induced synchronization in a distributed autooscillatory system described by the Ginzburg-Landau equations, which occur in a regime of chaotic spatiotemporal oscillations. A new regime of synchronous behavior, called incomplete noise-induced synchronization (INIS), is revealed, which can arise only in spatially distributed systems. The mechanism leading to the development of INIS in a distributed medium under the action of a distributed source of noise is analytically described. Good coincidence of analytical and numerical results is demonstrated.     

Soliton in fiber lasers beyond the Ginzburg-Landau equation approximation

Operation of a passively mode-locked fiber laser beyond the Ginzburg-Landau Equation (GLE) approximation is numerically investigated. It is found that even in the Maxwell-Bloch formalism stable solitary waves can still be obtained in the laser due to the cavity pulse peak clamping effect. We further show that the gain bandwidth plays a significant role in determining the detailed property of the formed solitary pulses.     

Stable vortex tori in the three-dimensional cubic-quintic Ginzburg-Landau equation

We demonstrate the existence of stable toroidal dissipative solitons with the inner phase field in the form of rotating spirals, corresponding to vorticity S=0, 1, and 2, in the complex Ginzburg-Landau equation with the cubic-quintic nonlinearity. The stable solitons easily self-trap from pulses with embedded vorticity. The stability is corroborated by accurate computation of growth rates for perturbation eigenmodes. The results provide the first example of stable vortex tori in a 3D dissipative medium, as well as the first example of higher-order tori (with S=2) in any nonlinear medium. It is found that all stable vortical solitons coexist in a large domain of the parameter space; in smaller regions, there coexist stable solitons with either S=0 and S=1, or S=1 and S=2.     

Nonequilibrium potential for the Ginzburg-Landau equation in the phase-turbulent regime

The steady state distribution functional of the supercritical complex Ginzburg-Landau equation with weak noise is determined asymptotically for long-wave-length fluctuations including the phaseturbulent regime. This is done by constructuring a non-equilibrium potential solving the Hamilton-Jacobi equation associated with the Fokker-Planck equation. The non-equilibrium potential serves as a Lyapunov functional. In parameter space it consists of two branches which are joined at the Benjamin-Feir instability. In the Benjamins-Feir stable regime the non-equilibrium potential has minima in the plane-wave attractors and our result generalizes to arbitrary dimension an earlier result for one dimension. Beyond the Benjamin-Feir instability the potential in the function space has a minimum which is degererate with respects to arbirary long-wavelength phase variations. The dynamics on the minimum set obey the generalized Kuramoto-Sivashinsky equation.