Dissertations / Theses: 'Ginzburg-Landau equation'

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Liu, Weigang. "A General Study of the Complex Ginzburg-Landau Equation." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/90886.

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In this dissertation, I study a nonlinear partial differential equation, the complex Ginzburg-Landau (CGL) equation. I first employed the perturbative field-theoretic renormalization group method to investigate the critical dynamics near the continuous non-equilibrium transition limit in this equation with additive noise. Due to the fact that time translation invariance is broken following a critical quench from a random initial configuration, an independent ``initial-slip'' exponent emerges to describe the crossover temporal window between microscopic time scales and the asymptotic long-time regime. My analytic work shows that to first order in a dimensional expansion with respect to the upper critical dimension, the extracted initial-slip exponent in the complex Ginzburg-Landau equation is identical to that of the equilibrium model A. Subsequently, I studied transient behavior in the CGL through numerical calculations. I developed my own code to numerically solve this partial differential equation on a two-dimensional square lattice with periodic boundary conditions, subject to random initial configurations. Aging phenomena are demonstrated in systems with either focusing and defocusing spiral waves, and the related aging exponents, as well as the auto-correlation exponents, are numerically determined. I also investigated nucleation processes when the system is transiting from a turbulent state to the ``frozen'' state. An extracted finite dimensionless barrier in the deep-quenched case and the exponentially decaying distribution of the nucleation times in the near-transition limit are both suggestive that the dynamical transition observed here is discontinuous. This research is supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award DE-FG02-SC0002308
Doctor of Philosophy
The complex Ginzburg-Landau equation is one of the most studied nonlinear partial differential equation in the physics community. I study this equation using both analytical and numerical methods. First, I employed the field theory approach to extract the critical initial-slip exponent, which emerges due to the breaking of time translation symmetry and describes the intermediate temporal window between microscopic time scales and the asymptotic long-time regime. I also numerically solved this equation on a two-dimensional square lattice. I studied the scaling behavior in non-equilibrium relaxation processes in situations where defects are interactive but not subject to strong fluctuations. I observed nucleation processes when the system under goes a transition from a strongly fluctuating disordered state to the relatively stable “frozen” state where its dynamics cease. I extracted a finite dimensionless barrier for systems that are quenched deep into the frozen state regime. An exponentially decaying long tail in the nucleation time distribution is found, which suggests a discontinuous transition. This research is supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award DE-FG02-SC0002308.

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Braun, Robert, and Fred Feudel. "Supertransient chaos in the two-dimensional complex Ginzburg-Landau equation." Universität Potsdam, 1996. http://opus.kobv.de/ubp/volltexte/2007/1409/.

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We have shown that the two-dimensional complex Ginzburg-Landau equation exhibits supertransient chaos in a certain parameter range. Using numerical methods this behavior is found near the transition line separating frozen spiral solutions from turbulence. Supertransient chaos seems to be a common phenomenon in extended spatiotemporal systems. These supertransients are characterized by an average transient lifetime which depends exponentially on the size of the system and are due to an underlying nonattracting chaotic set.

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Cruz-Pacheco, Gustavo. "The nonlinear Schroedinger limit of the complex Ginzburg-Landau equation." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187238.

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This work consists of a study of the complex Ginzburg-Landau equation (CGL) as a perturbation of the nonlinear Schrodinger equation (NLS) in one dimension under periodic boundary conditions. Using an averaging technique which is similar to a Melnikov method for pde's, necessary conditions are derived for the persistence of NLS solutions under the CGL perturbation. For the traveling wave solutions, these conditions are derived for a general nonlinearity and written explicitly as two equations for the two continuous parameters which determine the NLS traveling wave. It is shown using a Melnikov argument that in this case these two conditions are sufficient provided they satisfy a transversality condition. As a concrete example, the equations for the parameters are solved numerically in the important case of the CGL equation with a cubic nonlinearity. For the case of the CGL equation with a general power nonlinearity, it is proved that the NLS homoclinic orbits to rotating waves are destroyed by the CGL perturbation. Special attention is dedicated to the cubic case. For this nonlinearity, the NLS equation is a completely integrable Hamiltonian system and a much larger family of its solutions can be written explicitly. The necessary conditions for the persistence of the NLS isospectral manifold are written explicitly as a system of equations for the simple periodic eigenvalues. As an example, the conditions for an even genus two solution are written down as a system of three equations with three unknowns.

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Horsch, Karla 1968. "Attractors for Lyapunov cases of the complex Ginzburg-Landau equation." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282419.

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A special case of the complex Ginzburg-Landau (CGL) equation possessing a Lyapunov functional is identified. The global attractor of this Lyapunov CGL (LCGL) is studied in one spatial dimension with periodic boundary conditions. The LCGL may be viewed as a dissipative perturbation of the nonlinear Schrodinger equation (NLS), a completely integrable Hamiltonian system. The o-limit sets of the LCGL are identified as compact, connected unions of subsets of the stationary points of the flow. The stationary points do not depend on the strength of the perturbation, and so neither do the o-limit sets. However, the basins of attraction do depend sensitively on the perturbation strength. To determine the stability of the o-limit sets, the global Lyapunov functional is studied. Using the integrable NLS machinery, the second variation of the Lyapunov functional is diagonalized. An analysis of the diagonal elements yields that certain LCGL stationary points are stable. We are able to analyze the basins of attraction for a planar toy problem, which like the LCGL, is a dissipative perturbation of a Hamiltonian system. For this problem, almost every phase point is in a basin of attraction of an asymptotically stable stationary point. As the perturbation tends to zero, these basins become intermingled and the event of a fixed phase point being captured into a particular basin becomes probabilistic. Formulas for computing the probabilities of capture are given. These formulas are substantiated through a formal asymptotic analysis and numerical experiments. Such a probabilistic description of the basins of attraction is not completed for the infinite dimensional LCGL.

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Aguareles, Carrero Maria. "Interaction of spiral waves in the general complex Ginzburg-Landau equation." Doctoral thesis, Universitat Politècnica de Catalunya, 2007. http://hdl.handle.net/10803/5854.

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Molts sistemes físics tenen la propietat que la seva dinàmica ve definida per algun tipus de difussió espaial en competició amb un fenòmen de reacció, com per exemple en el cas de dos components químics que reaccionen al mateix temps que es difon l'un en el si de l'altre. La presència d'aquests dos fenòmens, la difusió i la reacció, sovint dóna lloc a patrons no homogenis de gran riquesa. Els models matemàtics que descriuen aquest tipus de comportament són normalment equacions en derivades parcials les solucions de les quals representen aquests patrons.

En aquesta tesi s'analitza l'equació de Ginzburg-Landau complexa general, que és una equació en derivades parcials de reacció-difusió que s'utilitza sovint com a model matemàtic per a descriure sistemes oscil·latoris en dominis extensos. En particular estudiem els patrons que sorgeixen en el pla quan s'imposa que el grau de Brouwer de la solució no sigui nul. Aquests patrons estan formats per ones de rotació en forma d'espirals, és a dir, les corbes de nivell de la solució formen espirals que emanen dels punts on la funció s'anul·la. Quan la solució s'anul·la només en un punt i per tant només hi ha una espiral, tota la dependència temporal apareix en el terme de freqüència. Així doncs, la funció solució es pot expressar com a funció del radi polar i en termes del seu grau topològic i la freqüència de l'ona. Per tant, aquestes solucions es poden expressar en termes d'un sistema d'equacions diferencials ordinàries. Aquestes solucions només existeixen per una certa freqüència que depèn unívocament dels paràmetres de l'equació i, com a conseqüència i degut a la relació de dispersió entre el nombre d'ones i la freqüència, el nombre d'ones a l'infinit, l'anomenat nombre d'ones asimptòtic, ve també determinat unívocament pels paràmetres. Quan les solucions tenen més d'un zero aïllat la condició sobre el grau de la funció fa que de cada zero sorgeixi una espiral diferent i aquestes es mouen en el pla mantenint la seva estructura local. En aquest treball s'usen tècniques d'anàlisi asimptòtica per trobar equacions del moviment per als centres de les espirals i es troba que aquesta evolució temporal és lenta. En concret, per la distàncies relatives grans entre els centres de les espirals, l'escala de temps per a la seva dinàmica ve donada pel logaritme de l'invers d'aquesta distància. Es demostra que aquestes equacions del moviment són diferents en funció de la relació entre els paràmetres de l'equació de Ginzburg-Landau complexa i la separació entre els centres de les espirals, i que la forma com es passa d'unes equacions a les altres és molt singular. També es demostra que el nombre d'ones asimptòtic per al cas de sistemes amb diverses espirals també està unívocament determinat pels paràmetres però no obstant, el cas de sistemes amb diverses espirals es diferencia del cas d'una única ona en què deixa de ser constant i evoluciona al mateix ritme que la velocitat dels centres de les espirals.
Many physical systems have the property that its dynamics is driven by some kind of spatical diffusion that is in competition with a reaction, like for instance two chemical species that react at the same time that there is a diffusion of each of them into the other. This interplay between reaction and diffusion produce non-homogeneous patterns that can sometimes be very rich. The mathematical models that describe this kind of behaviours are usually nonlinear partial differential equations whose solutions represent these patterns.

In this thesis we focus on an especific reaction-diffusion equation that is the so-called general complex Ginzburg-Landau equation that is used as a model for oscillatory systems in extended domains. In particular we are interested in the type of patterns in the plane that arise when the solutions have a non-vanishing Brouwer degree. These patterns have the property that they exhibit rotating waves in the shape of spirals, which means that the contour lines arrange in the shape of spirals that emerge from the points where the solution vanishes. When the solution vanishes only at one point all the time dependence appears as a frequency term so the solutions can be expressed as a function of the polar radius and in terms of the topological degree of the solution and the frequency of the wave. Therefore, these solutions can be expressed in terms of a system of ordinary differential equations. These solutions do only exist with a given frequency, and as a consequence and due to the existence of a dispresion relation, the wavenumber far from the origin, the so-called asymptotic wavenumber, is also unique. When the solutions have more than one isolated zero, the condition on the degree of the function has the effect of producing several spirals that emerge from the different zeros of the solution. These spirals evolve in time keeping their structure but moving around on the plane. In this work we use asymptotic analysis techniques to derive laws of motion for the centres of the spirals and we show that the time evolution of these patterns is slow and, for large relative separations of the centres of the spirals, the time scale for the their dynamics is logarithmic in the inverse of this distance. These laws of motion are different depending on the relation between the parameters of the complex Ginzburg-Landau equation and the relative separation of the spirals. We show that the way these laws change as the spirals separate or approach is highly singular. We also show that the asymptotic wavenumber in the case of multiple spirals is as well unique and that it evolves in time at the same rate as the velocity of the centres.

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Banaji, Murad. "Clustering and chaos in globally coupled oscillators." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249289.

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SNOUSSI, SEIFEDDINE. "Etude du comportement asymptotique des solutions d'une equation de ginzburg-landau generalisee." Paris 11, 1996. http://www.theses.fr/1996PA112060.

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L'objet de cette these est d'etudier les problemes d'existence locale ou globale de solutions d'un systeme couple d'une equation de ginzburg-landau generalisee et une equation de poisson ainsi qu'a l'etude de leur comportement asymptotique. Ce systeme est considere sur un domaine pouvant etre borne ou non-borne et les donnees initiales sont supposees etre de faible regularite. La premiere partie de cette these est consacree a l'etude du comportement asymptotique et qualitative des solutions de ce systeme quand il est considere sur un ouvert borne de la droite reelle ou du plan. On donnera des resultats d'existence globale ou d'explosion en temps fini. On etablira l'existence d'un attracteur dont on estimera la dimension de hausdorff ou fractale. Enfin, on etudiera les bifurcations de hopf sur un intervalle borne ou sur un ouvert mince du plan. Dans la deuxieme partie de cette these ce systeme sera considere sur un domaine non-borne. Cette partie est composee de deux chapitres. Dans le premier chapitre on etudie l'existence locale ou globale de solutions dans les espaces de sobolev ainsi que dans les espaces de sobolev a poids ayant des donnees initiales de faible regularite et on montrera que ces solutions se regularise en temps et on determinera en outre la nature de leur singularite a l'origine, leur existence globale en temps est aussi etudiee. Dans le deuxieme chapitre on s'interessera a l'etude du comportement asymptotique de ces solutions dans les espaces de sobolev a poids decroissant invariants par translation. On montrera l'existence d'un attracteur global attirant ces solutions dans la metrique des espaces de sobolev a poids

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Sauvageot, Myrto. "Modèle de Ginzburg-Landau : solutions radiales et branches de bifurcation." Paris 6, 2002. http://www.theses.fr/2002PA066548.

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Attanasio, Felipe [UNESP]. "Numerical study of the Ginzburg-Landau-Langevin equation: coherent structures and noise perturbation theory." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/92029.

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Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-21Bitstream added on 2014-06-13T19:12:26Z : No. of bitstreams: 1 attanasio_f_me_ift.pdf: 793752 bytes, checksum: 490b63eed4bdd7ec83984c78ac824d6d (MD5)
Nesta Dissertação apresentamos um estudo numéerico em uma dimensão espacial da equação de Ginzburg-Landau-Langevin (GLL), com ênfase na aplicabilidade de um método de perturbação estocástico e na mecânica estatística de defeitos topológicos em modelos de campos escalares reais. Revisamos brevemente conceitos de mecânica estatística de sistemas em equilíbrio e próximos a ele e apresentamos como a equação de GLL pode ser usada em sistemas que exibem transições de fase, na quantização estocástica e no estudo da interação de estruturas coerentes com fônons de origem térmica. Também apresentamos um método perturbativo, denominado teoria de perturbação no ruído (TPR), adequado para situações onde a intensidade do ruído estocástico é fraca. Através de simulações numéricas, investigamos a restauração de uma simetria 'Z IND. 2' quebrada, a aplicabilidade da TPR em uma dimensão e efeitos de temperatura finita numa solução topológica do tipo kink - onde apresentamos novos resultados sobre defeitos de dois kinks
In this Dissertation we present a numerical study of the GinzburgLandau-Langevin (GLL) equation in one spatial dimension, with emphasis on the applicability of a stochastic perturbative method and the statistical mechanics of topological defect structures in field-theoretic models of real scalar fields. We briefly review concepts of equilibrium and near-equilibrium statistical mechanics and present how the GLL equation can be used in systems that exhibit phase transitions, in stochastic quantization and in the study of the interaction of coherent structures with thermal phonons. We also present a perturbative method, named noise perturbation theory (NPT), suitable for situations where the stochastic noise intensity is weak. Through numerical simulations we investigate the restoration of a broken 'Z IND. 2' symmetry, the applicability of the NPT in one dimension and finite temperature effects on a topological kink solution - where we present new results on two-kink defects

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Attanasio, Felipe. "Numerical study of the Ginzburg-Landau-Langevin equation : coherent structures and noise perturbation theory /." São Paulo, 2013. http://hdl.handle.net/11449/92029.

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Orientador: Gastão Inácio Krein
Banca: Raquel Santos Marques de Carvalho
Banca: Ricardo D'Elia Matheus
Resumo: Nesta Dissertação apresentamos um estudo numéerico em uma dimensão espacial da equação de Ginzburg-Landau-Langevin (GLL), com ênfase na aplicabilidade de um método de perturbação estocástico e na mecânica estatística de defeitos topológicos em modelos de campos escalares reais. Revisamos brevemente conceitos de mecânica estatística de sistemas em equilíbrio e próximos a ele e apresentamos como a equação de GLL pode ser usada em sistemas que exibem transições de fase, na quantização estocástica e no estudo da interação de estruturas coerentes com fônons de origem térmica. Também apresentamos um método perturbativo, denominado teoria de perturbação no ruído (TPR), adequado para situações onde a intensidade do ruído estocástico é fraca. Através de simulações numéricas, investigamos a restauração de uma simetria 'Z IND. 2' quebrada, a aplicabilidade da TPR em uma dimensão e efeitos de temperatura finita numa solução topológica do tipo "kink" - onde apresentamos novos resultados sobre defeitos de dois kinks
Abstract: In this Dissertation we present a numerical study of the GinzburgLandau-Langevin (GLL) equation in one spatial dimension, with emphasis on the applicability of a stochastic perturbative method and the statistical mechanics of topological defect structures in field-theoretic models of real scalar fields. We briefly review concepts of equilibrium and near-equilibrium statistical mechanics and present how the GLL equation can be used in systems that exhibit phase transitions, in stochastic quantization and in the study of the interaction of coherent structures with thermal phonons. We also present a perturbative method, named noise perturbation theory (NPT), suitable for situations where the stochastic noise intensity is weak. Through numerical simulations we investigate the restoration of a broken 'Z IND. 2' symmetry, the applicability of the NPT in one dimension and finite temperature effects on a topological "kink" solution - where we present new results on two-kink defects
Mestre

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Stark, Donald Richard. "Structure and turbulence in the complex Ginzburg-Landau equation with a nonlinearity of arbitrary order." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187363.

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Numerical and analytical studies are undertaken for the "inviscid" limit of the complex Ginzburg-Landau (CGL) equation with the objective of studying the applicability of paradigms from finite dimensional dynamical systems and statistical mechanics to the case of an infinite dimensional dynamical system. The analytical results rely on exploiting the structure of this limit, which becomes the nonlinear Schrodinger (NLS) equation. In the NLS limit the CGL equation can exhibit strong spatio-temporal chaos. The initial growth of the bursts closely mimics the blowup solutions of the NLS equation. The study of this turbulent behavior focuses on the inertial range of the time-averaged wavenumber spectrum. Analytical estimates of the decay rate are constructed assuming both structure driven and homogeneous turbulence, and are compared with numerical simulations. The quintic case is observed to have a stronger decay rate than what is predicted by either theory. This reflects the dominance of dissipation in the dynamics. In the septic case, two distinct inertial ranges are observed. This combination suggests that the evolution of a single burst, on average, is predominantly due to the self-focusing mechanism of blowup NLS in the initial stage, and regularization effects of dissipation in the final stage. Because the initial stage is primarily influenced by the NLS structure, the rate of decay for this range is close to the decay predicted for the structure driven turbulence. In a numerical experiment it is observed that some NLS solutions survive the deformation due to a CGL perturbation. In some cases the question of persistence can be addressed analytically using an averaging technique similar to a Melnikov method for pde's.

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Mancas, Ciprian. "DISSIPATIVE SOLITONS IN THE CUBIC–QUINTIC COMPLEX GINZBURG–LANDAU EQUATION:BIFURCATIONS AND SPATIOTEMPORAL STRUCTURE." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2912.

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Comprehensive numerical simulations (reviewed in Dissipative Solitons, Akhmediev and Ankiewicz (Eds.), Springer, Berlin, 2005) of pulse solutions of the cubic--quintic Ginzburg--Landau equation (CGLE), a canonical equation governing the weakly nonlinear behavior of dissipative systems in a wide variety of disciplines, reveal various intriguing and entirely novel classes of solutions. In particular, there are five new classes of pulse or solitary waves solutions, viz. pulsating, creeping, snake, erupting, and chaotic solitons. In contrast to the regular solitary waves investigated in numerous integrable and non--integrable systems over the last three decades, these dissipative solitons are not stationary in time. Rather, they are spatially confined pulse--type structures whose envelopes exhibit complicated temporal dynamics. The numerical simulations also reveal very interesting bifurcations sequences of these pulses as the parameters of the CGLE are varied. In this dissertation, we develop a theoretical framework for these novel classes of solutions. In the first part, we use a traveling wave reduction or a so--called spatial approximation to comprehensively investigate the bifurcations of plane wave and periodic solutions of the CGLE. The primary tools used here are Singularity Theory and Hopf bifurcation theory respectively. Generalized and degenerate Hopf bifurcations have also been considered to track the emergence of global structure such as homoclinic orbits. However, these results appear difficult to correlate to the numerical bifurcation sequences of the dissipative solitons. In the second part of this dissertation, we shift gears to focus on the issues of central interest in the area, i.e., the conditions for the occurrence of the five categories of dissipative solitons, as well the dependence of both their shape and their stability on the various parameters of the CGLE, viz. the nonlinearity, dispersion, linear and nonlinear gain, loss and spectral filtering parameters. Our predictions on the variation of the soliton amplitudes, widths and periods with the CGLE parameters agree with simulation results. For this part, we develop and discuss a variational formalism within which to explore the various classes of dissipative solitons. Given the complex dynamics of the various dissipative solutions, this formulation is, of necessity, significantly generalized over all earlier approaches in several crucial ways. Firstly, the two alternative starting formulations for the Lagrangian are recent and not well explored. Also, after extensive discussions with David Kaup, the trial functions have been generalized considerably over conventional ones to keep the shape relatively simple (and the trial function integrable!) while allowing arbitrary temporal variation of the amplitude, width, position, speed and phase of the pulses. In addition, the resulting Euler--Lagrange equations are treated in a completely novel way. Rather than consider the stable fixed points which correspond to the well--known stationary solitons or plain pulses, we use dynamical systems theory to focus on more complex attractors viz. periodic, quasiperiodic, and chaotic ones. Periodic evolution of the trial function parameters on stable periodic attractors constructed via the method of multiple scales yield solitons whose amplitudes are non--stationary or time dependent. In particular, pulsating, snake (and, less easily, creeping) dissipative solitons may be treated in this manner. Detailed results are presented here for the pulsating solitary waves --- their regimes of occurrence, bifurcations, and the parameter dependences of the amplitudes, widths, and periods agree with simulation results. Finally, we elucidate the Hopf bifurcation mechanism responsible for the various pulsating solitary waves, as well as its absence in Hamiltonian and integrable systems where such structures are absent. Results will be presented for the pulsating and snake soliton cases. Chaotic evolution of the trial function parameters in chaotic regimes identified using dynamical systems analysis would yield chaotic solitary waves. The method also holds promise for detailed modeling of chaotic solitons as well. This overall approach fails only to address the fifth class of dissipative solitons, viz. the exploding or erupting solitons.
Ph.D.
Department of Mathematics
Sciences
Mathematics PhD

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Nersesyan, Vahagn. "Contrôle et mélange pour des équations stochastiques de Ginzburg-Landau et Schrödinger." Paris 11, 2008. http://www.theses.fr/2008PA112157.

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Cette thèse a pour objet l'étude des propriétés de contrôlabilité et de mélange pour des systèmes de Ginzburg-Landau et Schrödinger. Elle est divisée en trois parties. Dans la première partie, on étudie le problème d'ergodicité pour l'équation de Ginzburg-Landau complexe avec des perturbations aléatoires aux temps aléatoires. Le paramètre aléatoire est introduit par les perturbations et par les temps entre les perturbations. On montre que le processus de Markov associé à l'équation en question possède une unique mesure stationnaire et satisfait la propriété de mélange polynomial. La seconde partie porte sur le problème d'ergodicité des approximations fini-dimensionnelles de l'équation de Schrödinger. Le système est perturbé par un bruit multiplicatif scalaire. En utilisant la technique de couplage et un théorème sur les transformations des mesures, on montre que, sous des hypothèses naturelles sur le champs de vecteurs, le système en question admet une unique mesure stationnaire u sur la sphère unité S dans C^n, et que toutes les solutions convergent exponentiellement vers u en variation totale. Dans la troisième partie, on s'intéresse au problème de stabilisation pour l'équation de Schrödinger. On construit une loi u(z) qui force les trajectoires du système d'approcher faiblement dans H^2 de l'état propre. Ensuite on donne une application de notre résultat. On considère l'équationde Schrödinger avec un potentiel qui a une amplitude aléatoire dépendant du temps. On montre que si la distribution de l'amplitude est suffisamment non dégénérée, alors toute solution du système est presque sûrement non bornée dans les espaces de Sobolev
This thesis aims to study the problems of controllability and mixing for systems of Ginzburg-Landau and Schrödinger. It is divided into three parts. We begin with the problem of ergodicity for the complex Ginzburg-Landau equation perturbed by an unbounded random kick-force. Randomness is introduced both through the kicks and through the times between the kicks. We show that the Markov process associated with the equation in question possesses a unique stationary distribution and satisfies aproperty of polynomial mixing. In the second part, we consider the finite-dimensional approximations of the Schrödinger equation. The system is driven by a multiplicative scalar noise. Using the coupling method and a measure transformation theorem, we show that, under some natural hypotheses on vector field, the system has a unique stationary measure u on the unit sphere S in C^n, and any solution converges exponentially fast to the measure u in the variational norm. The third part is devoted to the problem of stabilization of the Schrödinger equation. We construct a feedback law u(z),which forces the trajectories of system to approach the eigenstatein H^2-weak sense. Then we give an application of our result. We consider the Schrödinger equation with a potential which has a random time-dependent amplitude. We show that if the distribution of the amplitude is sufficiently non-degenerate, then any trajectory of system is almost surely non-bounded in Sobolev spaces

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Chugreeva, Olga [Verfasser], Christof Erich [Akademischer Betreuer] Melcher, and Maria Gabrielle [Akademischer Betreuer] Westdickenberg. "Stochastics meets applied analysis : stochastic Ginzburg-Landau vortices and stochastic Landau-Lifshitz-Gilbert equation / Olga Chugreeva ; Christof Erich Melcher, Maria Gabrielle Westdickenberg." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1156922305/34.

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Kamagate, Aladji. "Propagation des solitons spatio-temporels dans les milieux dissipatifs." Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS068/document.

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Ce mémoire de thèse présente une approche semi-analytique des différentes solutions solitons spatio-temporelles de l'équation cubique quintique de Ginzburg-Landau complexe étendue à (3+1)D (GL3D).La méthode semi-analytique choisie est celle des coordonnées collectives qui permet d'approcher le champ exact, dont l'expression analytique est inconnue, par une fonction d'essai, qui comporte un nombre limité de paramètres physiques.En appliquant cette procédure à l'équation GL3D, nous obtenons un système d'équations variationnelles qui gouverne l'évolution des paramètres de la balle de lumière. Nous montrons que cette approche des coordonnées collectives est incomparablement plus rapide que la procédure de résolution directe de l'équation GL3D. cette rapidité permet d'obtenir, en un temps record, une cartographie générale des comportements dynamiques des balles de lumière. Cette cartographie révèle une riche variété d'états dynamiques faite de balles de lumière stationnaires, oscillantes et rotatives.Finalement, les résultats de cette thèse prédisent l'existence de plusieurs familles de balles de lumière, et précisent les domaines respectifs de leurs paramètres physiques. Cette prédiction constitue un pas en avant dans les efforts entrepris ces dernières années en vue d'une démonstration expérimentale de ce type d'impulsions
This thesis presents a semi-analytical approach for the search of (3+1)D spatio-temporal soliton solutions of the complex cubic-quintic Ginzburg-Landau equation (GL3D).We use a semi-analytical method called collective coordinate approach, to obtain an approximate profile of the unknown pulse field. This ansatz function is chosen to be a function of a finite number of parameters describing the light pulse.By applying this collective corrdinate procedure to the GL3D equation, we obtain a system of variational equations which give the evolution of the light bullet parameters as a function of the propagation distance. We show that the collective coordinate approach is uncomparably faster than the direct numerical simulation of the propagation equation. This permits us to obtain, efficiently, a global mapping of the dynamical behavior of light bullets, which unveils a rich variety of dynamical states comprising stationary, pulsating and rotating light bullets.Finally the existence of several types of light bullets is predicted in specific domains of the equation parameters. Altogether, this theoretical and numerical work may be a useful tool next to the efforts undertaken these last years observing light bullets experimentally

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Miot, Evelyne. "Quelques problèmes relatifs à la dynamique des points vortex dans les équations d'Euler et de Ginzburg-Landau complexe." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00444820.

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Les problèmes étudiés dans cette thèse ont trait à la dynamique des points vortex dans deux équations pour les fluides ou superfluides bidimensionnels. La première partie est dévolue à l'équation d'Euler incompressible. Nous y analysons le système mixte Euler-points vortex, introduit par Marchioro et Pulvirenti, qui décrit l'évolution d'un tourbillon obtenu par superposition de points vortex et d'une composante plus régulière. Nous examinons diverses problématiques telles que le lien entre les points de vue lagrangien et eulérien, l'unicité, l'existence et l'expansion du support du tourbillon. La seconde partie de la thèse est consacrée à une équation de Ginzburg-Landau complexe obtenue en ajoutant un terme de dissipation à l'équation de Gross-Pitaevskii. Après avoir examiné le problème de Cauchy dans l'espace d'énergie correspondant, nous étudions la dynamique des points vortex dans le cadre de données très bien préparées. Dans un dernier temps, nous considérons un autre régime asymptotique, sans vortex, dans lequel les solutions sont des perturbations de champs constants de module égal à un. Une dynamique de type ondes amorties pour la perturbation est mise en évidence.

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Lebellego, Marion. "Phénomènes ondulatoires dans un modèle discret de faille sismique." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1400/.

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Dans cette thèse on s'intéresse à des phénomènes ondulatoires dans un modèle discret de faille sismique introduit par Burridge et Knopoff, constitué d'une chaîne de patins-ressorts, et dans lequel des mouvements de type glissement-saccadé (stick-slip), caractéristiques du phénomène de tremblement de terre, sont observés numériquement. Dans la première partie, on considère une version introduite par Carlson et Langer, avec loi de frottement de type velocity-weakening (adoucissement du frottement avec la vitesse de glissement). Cette loi est non lisse et multivaluée en 0. Les équations du mouvement sont alors constituées d'un système infini d'inclusions différentielles couplées. On démontre en se basant sur la méthode de Lyapounov-Schmidt, l'existence d'ondes périodiques progressives dans une limite de faible couplage entre les masses. Dans la deuxième partie, on étudie ce modèle avec une loi de frottement de type rate-and-state qui prend en compte l'état de l'interface entre les deux plaques sismiques. La loi de frottement est lisse, mais dépend d'une variable d'état supplémentaire. On dérive formellement une équation de Ginzburg-Landau comme équation d'amplitude et on montre qu'il existe des petites solutions du système décrites par cette équation d'amplitude, lorsque celui-ci se trouve au seuil de l'instabilité et sur une échelle de temps suffisamment grande
In this thesis, we consider a simple version of the spring-block model of Burridge-Knopoff for seismic faults, in which stick-slip instabilities have been numerically observed (phenomena corresponding to earthquakes). In the first part, we consider the version of this model introduced by Carlson and Langer, in which the friction law is of type velocity-weakening. This law is nonsmooth and multivalued at zero sliding velocity. As equations of motion, we obtain an infinite system of coupled differential inclusions. We prove, using the Lyapounov-Schmidt reduction, that there exist periodic travelling waves in this system in a limit of weak coupling between the masses. In the second part, we consider the model combined with a rate-and-state friction law, taking into account the ageing of the interface. The friction law is smooth but depends on an additive variable accounting for the state of the surface. In this part, we formally derive a Ginzburg-Landau equation as a modulation equation and prove that there exist small solutions in our system, that can be described by this equation in a sufficiently large time-scale, when the system lies at the threshold of instability

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Brusch, Lutz. "Complex Patterns in Extended Oscillatory Systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2001. http://nbn-resolving.de/urn:nbn:de:swb:14-1006416783250-74051.

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Ausgedehnte dissipative Systeme können fernab vom thermodynamischen Gleichgewicht instabil gegenüber Oszillationen bzw. Wellen oder raumzeitlichem Chaos werden. Die komplexe Ginzburg-Landau Gleichung (CGLE) stellt ein universelles Modell zur Beschreibung dieser raumzeitlichen Strukturen dar. Diese Arbeit ist der theoretischen Analyse komplexer Muster gewidmet. Mittels numerischer Bifurkations- und Stabilitätsanalyse werden Instabilitäten einfacher Muster identifiziert und neuartige Lösungen der CGLE bestimmt. Modulierte Amplitudenwellen (MAW) und Super-Spiralwellen sind Beispiele solcher komplexer Muster. MAWs können in hydrodynamischen Experimenten und Super-Spiralwellen in der Belousov-Zhabotinsky-Reaktion beobachtet werden. Der Grenzübergang von Phasen- zu Defektchaos wird durch den Existenzbereich der MAWs erklärt. Mittels der selben numerischen Methoden wird Bursting vom Fold-Hopf-Typ in einem Modell der Kalziumsignalübertragung in Zellen identifiziert.

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Pascolati, Mauro Cesar Videira [UNESP]. "Dinâmica de vórtices em filmes finos supercondutores de superfície variável." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/99728.

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O interesse em conhecer o comportamento supercondutor tem sido cada vez maior nas últimas décadas. Na busca de melhores características supercondutoras, descobriu-se que amostras volumétricas apresentam características muito diferentes de amostras mesoscópicas (amostras com dimensões próximas dos comprimentos de penetração de London e coerência). Como exemplo, podemos citar a não formação de rede de Abrikosov, como consequência do efeito de confinamento (efeito associado às dimensões reduzidas da amostra) e também uma mudança considerável nos valores dos campos críticos. Neste trabalho foram resolvidas as equações de Ginzburg-Landau dependentes do tempo (TDGL), para fazer uma análise detalhada da dinâmica de vórtices em filmes finos mesoscópicos. Para revolvê-las, utilizamos o método das variáveis de ligação com invariância de calibre, adaptado para o algoritmo de diferenças finitas, utilizado para obter a densidade dos pares de Cooper e também curvas de magnetização. O estudo dessa dinâmica de vórtices, foi feito em três amostras com superfícies geométricas diferentes (côncova, convexa e rugosa). Observamos que na comparação entre as duas primeiras, há uma diferença considerável nos valores dos campos críticos, bem como no comportamento da magnetização comparado com um filme plano. Já para a amostra de superfície rugosa, observamos que existe uma competição entre o efeito de confinamento e a rugosidade em relação à configuração dos vórtices. Apresentamos também, uma tabela que mostra resumidamente os estados estacionários dos vórtices nas três amostras.
The interest to investigate the investigate the behavior of a superconductor has grown in the last few decades. Having in mind to search for better superconducting characteristics, it has been found that bulk samples present characteristics much more different than mesoscopic samples (samples with dimensions of the same order of the same order of the London penetration length and the coherence length). As an example, we can mention the non-formation of an Abrikosov vortex lattice as a consequence of the confinement effect (effect associated with the reduced dimensions of the sample) and also considerable change in the critical field values. In the present work we solved the time dependent Ginzburg-Landau equation (TDGL), in order to make a detailed analysis of the vortex dynamics in mesoscopic thin films. To solve these equations, we have used the link variables method which is gauge invariant. From this, we obtain the Cooper pair density and the magnetization curves. The vortex dynamics was investigated for three different surfaces of the film (concave, convex, and irregular). We have observed that, with respect to the parabolic geometries, there is a considerable difference for the critical fields, as well as for the behavior of the magnetization compared to a flat film. On the other hand, for a sample with an irregular surface, we have seen that there is a competition between the confinement effect and rugosity with respect to vortex configurations. We also present a table which summarizes the vortex stationary states for the three topologies mentioned above.

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Pascolati, Mauro Cesar Videira. "Dinâmica de vórtices em filmes finos supercondutores de superfície variável /." Bauru : [s.n.], 2010. http://hdl.handle.net/11449/99728.

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Resumo: O interesse em conhecer o comportamento supercondutor tem sido cada vez maior nas últimas décadas. Na busca de melhores características supercondutoras, descobriu-se que amostras volumétricas apresentam características muito diferentes de amostras mesoscópicas (amostras com dimensões próximas dos comprimentos de penetração de London e coerência). Como exemplo, podemos citar a não formação de rede de Abrikosov, como consequência do efeito de confinamento (efeito associado às dimensões reduzidas da amostra) e também uma mudança considerável nos valores dos campos críticos. Neste trabalho foram resolvidas as equações de Ginzburg-Landau dependentes do tempo (TDGL), para fazer uma análise detalhada da dinâmica de vórtices em filmes finos mesoscópicos. Para revolvê-las, utilizamos o método das variáveis de ligação com invariância de calibre, adaptado para o algoritmo de diferenças finitas, utilizado para obter a densidade dos pares de Cooper e também curvas de magnetização. O estudo dessa dinâmica de vórtices, foi feito em três amostras com superfícies geométricas diferentes (côncova, convexa e rugosa). Observamos que na comparação entre as duas primeiras, há uma diferença considerável nos valores dos campos críticos, bem como no comportamento da magnetização comparado com um filme plano. Já para a amostra de superfície rugosa, observamos que existe uma competição entre o efeito de confinamento e a rugosidade em relação à configuração dos vórtices. Apresentamos também, uma tabela que mostra resumidamente os estados estacionários dos vórtices nas três amostras.
Abstract: The interest to investigate the investigate the behavior of a superconductor has grown in the last few decades. Having in mind to search for better superconducting characteristics, it has been found that bulk samples present characteristics much more different than mesoscopic samples (samples with dimensions of the same order of the same order of the London penetration length and the coherence length). As an example, we can mention the non-formation of an Abrikosov vortex lattice as a consequence of the confinement effect (effect associated with the reduced dimensions of the sample) and also considerable change in the critical field values. In the present work we solved the time dependent Ginzburg-Landau equation (TDGL), in order to make a detailed analysis of the vortex dynamics in mesoscopic thin films. To solve these equations, we have used the link variables method which is gauge invariant. From this, we obtain the Cooper pair density and the magnetization curves. The vortex dynamics was investigated for three different surfaces of the film (concave, convex, and irregular). We have observed that, with respect to the parabolic geometries, there is a considerable difference for the critical fields, as well as for the behavior of the magnetization compared to a flat film. On the other hand, for a sample with an irregular surface, we have seen that there is a competition between the confinement effect and rugosity with respect to vortex configurations. We also present a table which summarizes the vortex stationary states for the three topologies mentioned above.
Orientador: Paulo Noronha Lisboa Filho
Coorientador: Edson Sardella
Banca: Wilson Aires Ortiz
Banca: Clelio Clemente de Souza Silva
Mestre

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21

Chiron, David. "Etude mathématique de modèles issus de la physique de la matière condensée." Paris 6, 2004. http://www.theses.fr/2004PA066053.

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22

Blockley, Edward William. "Nonlinear solutions of the amplitude equations governing fluid flow in rotating spherical geometries." Thesis, University of Exeter, 2008. http://hdl.handle.net/10036/41950.

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We are interested in the onset of instability of the axisymmetric flow between two concentric spherical shells that differentially rotate about a common axis in the narrow-gap limit. The expected mode of instability takes the form of roughly square axisymmetric Taylor vortices which arise in the vicinity of the equator and are modulated on a latitudinal length scale large compared to the gap width but small compared to the shell radii. At the heart of the difficulties faced is the presence of phase mixing in the system, characterised by a non-zero frequency gradient at the equator and the tendency for vortices located off the equator to oscillate. This mechanism serves to enhance viscous dissipation in the fluid with the effect that the amplitude of any initial disturbance generated at onset is ultimately driven to zero. In this thesis we study a complex Ginzburg-Landau equation derived from the weakly nonlinear analysis of Harris, Bassom and Soward [D. Harris, A. P. Bassom, A. M. Soward, Global bifurcation to travelling waves with application to narrow gap spherical Couette flow, Physica D 177 (2003) p. 122-174] (referred to as HBS) to govern the amplitude modulation of Taylor vortex disturbances in the vicinity of the equator. This equation was developed in a regime that requires the angular velocities of the bounding spheres to be very close. When the spherical shells do not co-rotate, it has the remarkable property that the linearised form of the equation has no non-trivial neutral modes. Furthermore no steady solutions to the nonlinear equation have been found. Despite these challenges Bassom and Soward [A. P. Bassom, A. M. Soward, On finite amplitude subcritical instability in narrow-gap spherical Couette flow, J. Fluid Mech. 499 (2004) p. 277-314] (referred to as BS) identified solutions to the equation in the form of pulse-trains. These pulse-trains consist of oscillatory finite amplitude solutions expressed in terms of a single complex amplitude localised as a pulse about the origin. Each pulse oscillates at a frequency proportional to its distance from the equatorial plane and the whole pulse-train is modulated under an envelope and drifts away from the equator at a relatively slow speed. The survival of the pulse-train depends upon the nonlinear mutual-interaction of close neighbours; as the absence of steady solutions suggests, self-interaction is inadequate. Though we report new solutions to the HBS co-rotation model the primary focus in this work is the physically more interesting case when the shell velocities are far from close. More specifically we concentrate on the investigation of BS-style pulse-train solutions and, in the first part of this thesis, develop a generic framework for the identification and classification of pulse-train solutions. Motivated by relaxation oscillations identified by Cole [S. J. Cole, Nonlinear rapidly rotating spherical convection, Ph.D. thesis, University of Exeter (2004)] whilst studying the related problem of thermal convection in a rapidly rotating self-gravitating sphere, we extend the HBS equation in the second part of this work. A model system is developed which captures many of the essential features exhibited by Cole's, much more complicated, system of equations. We successfully reproduce relaxation oscillations in this extended HBS model and document the solution as it undergoes a series of interesting bifurcations.

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23

MacKenzie, Tony. "Create accurate numerical models of complex spatio-temporal dynamical systems with holistic discretisation." University of Southern Queensland, Faculty of Sciences, 2005. http://eprints.usq.edu.au/archive/00001466/.

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This dissertation focuses on the further development of creating accurate numerical models of complex dynamical systems using the holistic discretisation technique [Roberts, Appl. Num. Model., 37:371-396, 2001]. I extend the application from second to fourth order systems and from only one spatial dimension in all previous work to two dimensions (2D). We see that the holistic technique provides useful and accurate numerical discretisations on coarse grids. We explore techniques to model the evolution of spatial patterns governed by pdes such as the Kuramoto-Sivashinsky equation and the real-valued Ginzburg-Landau equation. We aim towards the simulation of fluid flow and convection in three spatial dimensions. I show that significant steps have been taken in this dissertation towards achieving this aim. Holistic discretisation is based upon centre manifold theory [Carr, Applications of centre manifold theory, 1981] so we are assured that the numerical discretisation accurately models the dynamical system and may be constructed systematically. To apply centre manifold theory the domain is divided into elements and using a homotopy in the coupling parameter, subgrid scale fields are constructed consisting of actual solutions of the governing partial differential equation(pde). These subgrid scale fields interact through the introduction of artificial internal boundary conditions. View the centre manifold (macroscale) as the union of all states of the collection of subgrid fields (microscale) over the physical domain. Here we explore how to extend holistic discretisation to the fourth order Kuramoto-Sivashinsky pde. I show that the holistic models give impressive accuracy for reproducing the steady states and time dependent phenomena of the Kuramoto-Sivashinsky equation on coarse grids. The holistic method based on local dynamics compares favourably to the global methods of approximate inertial manifolds. The excellent performance of the holistic models shown here is strong evidence in support of the holistic discretisation technique. For shear dispersion in a 2D channel a one-dimensional numerical approximation is generated directly from the two-dimensional advection-diffusion dynamics. We find that a low order holistic model contains the shear dispersion term of the Taylor model [Taylor, IMA J. Appl. Math., 225:473-477, 1954]. This new approach does not require the assumption of large x scales, formerly absolutely crucial in deriving the Taylor model. I develop holistic discretisation for two spatial dimensions by applying the technique to the real-valued Ginzburg-Landau equation as a representative example of second order pdes. The techniques will apply quite generally to second order reaction-diffusion equations in 2D. This is the first study implementing holistic discretisation in more than one spatial dimension. The previous applications of holistic discretisation have developed algebraic forms of the subgrid field and its evolution. I develop an algorithm for numerical construction of the subgrid field and its evolution for 1D and 2D pdes and explore various alternatives. This new development greatly extends the class of problems that may be discretised by the holistic technique. This is a vital step for the application of the holistic technique to higher spatial dimensions and towards discretising the Navier-Stokes equations.

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Komninos, Paulo Guilherme. "Análise da dinâmica do funcionamento de lasers de fibra dopada com Érbio sob a óptica da equação de Ginzburg-Landau." Universidade Presbiteriana Mackenzie, 2011. http://tede.mackenzie.br/jspui/handle/tede/1404.

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This work presents a study based on the numerical analysis of Erbium-doped fiber lasers using the technique of passive mode-locking for the laser working in pulsed regime. The equation describing the dynamics of a laser cavity is known as Ginzburg-Landau Equation, that in this work is solved numerically by the Split-Step Fourier Method. By this method, an algorithm was developed which was incorporated into the MATLAB environment so taht numerical calculations were made. The method was validated by comparing the results generated by the program (temporal pulse width due to the gain of the cavity with and without dispersion and nonlinearity) with the results published in literature. After validation of the method an experimental results were reproduced of an Erbium-doped fiber laser using thin films of carbon nanotubes as saturable absorbers. The laser generates a bandwidth of 5.7 nm for a cavity with a total length of 9 m. This experimental result was used as a calibration parameter in the initial simulations. Just by varying the length of the cavity in the simulation, results very close to the experiment were obtained. These results have helped in understanding some of the experimental variables.
Neste trabalho é apresentado um estudo baseado em análise numérica de lasers à fibra dopada com Érbio utilizando a técnica de acoplamento passivo de modos para que o mesmo opere em regime pulsado. A equação que descreve a dinâmica de uma cavidade laser é conhecida como Equação de Ginzburg-Landau, que neste trabalho é resolvida numericamente pelo Método Split-Step Fourier. Por este método, foi desenvolvido um algoritmo que foi incorporado ao ambiente MATLAB para serem feitos os cálculos numéricos. O método foi validado comparando os resultados gerados pelo programa (largura temporal do pulso devido ao ganho da cavidade com e sem dispersão e não-linearidade) com os resultados publicados na literatura. Após a validação do método, foram reproduzidos resultados experimentais de um laser a fibra dopada com Érbio usando como absorvedor saturável filmes finos de nanotubos de carbono. O laser gera uma largura de banda de 5,7 nm para uma cavidade de comprimento total de 9 m. Este resultado experimental foi utilizado como parâmetro de calibração inicial nas simulações. Apenas variando o comprimento da cavidade na simulação, foram obtidos resultados bem próximos ao do experimento. Esses resultados ajudaram na compreensão de algumas variáveis do experimento.

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Risler, Ronan Thomas. "Comportement critique d'oscillateurs couplés : groupe de renormalisation et classe d'universalité." Paris 6, 2003. https://tel.archives-ouvertes.fr/tel-00004449v2.

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Besse, Valentin. "Dynamique spatiale de la lumière et saturation de l’effet Kerr." Thesis, Angers, 2014. http://www.theses.fr/2014ANGE0030/document.

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Nous présentons une étude de la dynamique de la lumière et des mesures des caractéristiques non-linéaires optiques dans le disulfure de carbone.Dans la première partie, nous calculons dans le cadre d’un modèle classique des expressions des susceptibilités non-linéaires jusqu’au cinquième ordre, en tenant compte des corrections de champ local. Nous formulons diﬀérentes hypothèses que nous conﬁrmons ou inﬁrmons par la mesure des indices d’absorption et de réfraction non-linéaires. Celles-ci sont obtenues en combinant deux méthodes de caractérisation des non-linéarités au sein d’un système 4fd’imagerie. L’analyse des données expérimentales utilise une méthode nouvellement développée, qui consiste à inverser numériquement, par la méthode de Newton, les solutions analytiques des équations diﬀérentielles qui décrivent l’évolution du faisceau.Dans la deuxième partie, nous observons la ﬁlamentation d’un faisceau laser à la longueur d’onde de 532 nm et en régime picoseconde. Puis nous procédons à la mesure de l’indice de réfraction non-linéaire eﬀectif du troisième ordre n2,eﬀ en fonction de l’intensité incidente. Par un ajustement de la courbe de saturation de l’eﬀet Kerr,nous développons un nouveau modèle. La résolution numérique de celui-ci reproduit la ﬁlamentation observée.La dernière partie est consacrée à l’étude de la dynamique des solitons dissipatifs au sein de milieux à gains et pertes non-linéaires. La résolution numérique de l’équation complexe de Ginzburg-Landau cubique-quintique est réalisée suivant diﬀérentes conﬁgurations :soliton fondamental, dipôle, quadrupôle,vortex carré et rhombique
We present a study of light dynamics and measurements of the nonlinear optical characteristics of carbon disulphide. In the ﬁrst part, we calculate using the classical model, the nonlinear susceptibilities up to the ﬁfth order taking into account local ﬁeld corrections. We express diﬀerent assumptions that we conﬁrm or refute by measuring the nonlinear absorption coeﬃcient and the nonlinear refractive index. The measurements are performed by means of two nonlinear characterization methods combined with an imaging 4f system. We analyse the experimental data using a newly developed method which numerically inverts the analytical solutions of the diﬀerential equations which describe the evolution of the beam, using Newton’s method. In the second part, we observe light ﬁlamentation at wavelength 532 nm, in the picoseconds regime. Then we measure the eﬀective third order nonlinear refractive index n2,eﬀ versus the incident intensity. By ﬁtting the curve of the Kerr eﬀect saturation, we develop a new model. Numerically solving this model, allows us to reproducethe experimentally observed ﬁlamentation. The last part is dedicated to the study of dissipative solitons dynamics. The complex Ginzburg-Landau equation with cubic-quintic nonlineraties is numerically solved in various conﬁgurations : soliton fundamental dipole, quadrupole, vortex and square rhombic

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Baraket, Sami. "Quelques résultats sur des équations aux dérivées partielles non linéaires provenant de problèmes géométriques." Cachan, Ecole normale supérieure, 1994. http://www.theses.fr/1994DENS0012.

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Dans ce travail on s'intéresse à des solutions de problèmes variationnels intervenant en géométrie ou en physique, minimisantes ou non. Nous avons étudié plus particulièrement les applications harmoniques entre variétés riemanniennes et les solutions du système de Ginzburg-Landau. Nous donnons plusieurs résultats d'analyse asymptotique de ces solutions lorsque l'on fait varier certains paramètres significatifs. Des problèmes analogues aux applications harmoniques provenant de la physique, telle l'équation de Landau-Lifschitz ont été résolus

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Nguyen, Hoang Phuong. "Résultats de compacité et régularité dans un modèle de Ginzburg-Landau non-local issu du micromagnétisme. Lemme de Poincaré et régularité du domaine." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30315.

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Dans cette thèse, nous étudions des problèmes aux limites impliquant le modèle micro-magnétique et les formes différentielles. Dans la première partie, nous considérons un modèle non-local de Ginzburg-Landau apparaissant en micromagnétisme avec une condition au bord de type Dirichlet. Le modèle typique implique une fonctionelle d'énergie définie pour des applications des valeurs dans la sphère S² et qui depend de plusieurs paramètres, qui représentent des quantités physiques. Une première question concerne la compacité des aimantations ayant les énergies de quelques parois de Néel de longueur finie et des défauts topologiques lorsque ces paramètres convergent vers 0. Notre méthode utilise des techniques développées pour les problèmes de type Ginzburg-Landau sur la concentration d'énergie autour des vortex, avec un argument d'approximation des champs de vecteurs dans S² par des champs de vecteurs dans S¹ éloignés des vortex. Nous effectuons également en détail la preuve de la régularité C^infini à l'intérieur et la régularité C(^1,alpha) au bord, pour tous les alpha appartiennent à (0, 1/2 ), des points critiques du modèle. Dans la deuxième partie, nous étudions le lemme de Poincaré qui affirme que sur un domaine simplement connexe chaque forme fermée est exacte. Nous prouvons le lemme de Poincaré sur un domaine avec une condition aux limites de Dirichlet sous une hypothèse naturelle sur la régularité du domaine : une forme fermée ƒ dans l'espace C(^r,alpha) est la différentielle d'une forme C(^r+1,alpha) à condition que le domaine lui-même soit C(^r+1,alpha). La preuve est basée sur une construction par approximation, avec un argument de dualité. Nous établissons également le résultat correspondant dans le cadre d'espaces de Sobolev d'ordre supérieur
In this thesis, we study some boundary value problems involving micromagnetic models and differential forms. In the first part, we consider a nonlocal Ginzburg-Landau model arising in micromagnetics with an imposed Dirichlet boundary condition. The model typically involves S²-valued maps with an energy functional depending on several parameters, which represent physical quantities. A first question concerns the compactness of magnetizations having the energies of several Néel walls of finite length and topo- logical defects when these parameters converge to 0. Our method uses techniques developed for Ginzburg-Landau type problems for the concentration of energy on vortex balls, together with an approximation argument of S²-valued vector fields by S¹-valued vector fields away from the vortex balls. We also carry out in detail the proofs of the C^infinite regularity in the interior and C(^1,alpha) regularity up to the boundary, for all alpha belong to (0, 1/2), of critical points of the model. In the second part, we study the Poincaré lemma, which states that on a simply connected domain every closed form is exact. We prove the Poincaré lemma on a domain with a Dirichlet boundary condition under a natural assumption on the regularity of the domain: a closed form ƒ in the Hölder space C(^r,alpha) is the differential of a C(^r+1,alpha) form, provided that the domain itself is C(^r+1,alpha). The proof is based on a construction by approximation, together with a duality argument. We also establish the corresponding statement in the setting of higher order Sobolev spaces

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29

Kamagaté, Aladji. "Propagation des solitons spatio-temporels dans les milieux dissipatifs." Phd thesis, Université de Bourgogne, 2010. http://tel.archives-ouvertes.fr/tel-00671172.

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Ce mémoire de thèse présente une approche semi-analytique des différentes solutions solitons spatio-temporelles de l'équation cubique quintique de Ginzburg-Landau complexe étendue à (3+1)D (GL3D).La méthode semi-analytique choisie est celle des coordonnées collectives qui permet d'approcher le champ exact, dont l'expression analytique est inconnue, par une fonction d'essai, qui comporte un nombre limité de paramètres physiques.En appliquant cette procédure à l'équation GL3D, nous obtenons un système d'équations variationnelles qui gouverne l'évolution des paramètres de la balle de lumière. Nous montrons que cette approche des coordonnées collectives est incomparablement plus rapide que la procédure de résolution directe de l'équation GL3D. cette rapidité permet d'obtenir, en un temps record, une cartographie générale des comportements dynamiques des balles de lumière. Cette cartographie révèle une riche variété d'états dynamiques faite de balles de lumière stationnaires, oscillantes et rotatives.Finalement, les résultats de cette thèse prédisent l'existence de plusieurs familles de balles de lumière, et précisent les domaines respectifs de leurs paramètres physiques. Cette prédiction constitue un pas en avant dans les efforts entrepris ces dernières années en vue d'une démonstration expérimentale de ce type d'impulsions.

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30

Herbert, Geoffrey M. "Stability analysis of the Fisher and Landau-Ginzburg equations." Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307124.

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Cross, Simon. "Localised solutions of the parametrically driven Ginzburg-Landau and nonlinear Schrӧdinger equations." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/4876.

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Includes bibliographical references.
This thesis deals with localised solutions of the parametrically driven Ginzburg-Landau equation and its nonlinear Schrӧdinger limit. We begin with a detailed analysis of the Faraday Resonance experiment, in which the driven complex Ginzburg-Landau equation (CGLE) arises, and an examination of how the CGLE appears as the amplitude equation for the modes excited near a Hopf bifurcation.

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32

Lam, Chun-kit, and 林晉傑. "The dynamics of wave propagation in an inhomogeneous medium: the complex Ginzburg-Landau model." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40887881.

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Lam, Chun-kit. "The dynamics of wave propagation in an inhomogeneous medium the complex Ginzburg-Landau model /." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40887881.

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Radulescu, Vicentiu. "Analyse de quelques problèmes liés à l'équation de Ginzburg-Landau." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1995. http://tel.archives-ouvertes.fr/tel-00980811.

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35

Carty, James George. "Studies of coated and polycrystalline superconductors using the time dependant Ginzburg-Landau equations." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2656/.

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Time-dependent Ginzburg-Land au equations are used to model 2D and 3D systems containing both superconductors and normal metals, in which both T(_c) and normal-state resistivity are spatially dependent. The equations are solved numerically using an efficient semi-implicit Crank-Nicolson algorithm. The algorithm, is used to model flux entry and exit in homogenous superconductors with metallic coatings of different resistivities. For an abrupt boundary there is a minimum field of initial vortex entry occurring at a kappa-dependent finite ratio of the normal-state resistivities of the superconductor and the normal metal. Highly reversible magnetization characteristics are achieved using a diffusive layer several coherence lengths wide between the superconductor and the normal metal. This work provides the first TD GL simulation in both 2D and 3D of current flow in polycrystalline superconductors, and provides some important new results both qualitative and quantitative. Using a magnetization method we obtain Jc for both 2D and 3D systems, and obtain the correct field and kappa dependences in 3D, given by F = 3.6 x 10-4 B}l (T) (1- b)2. The pre-factor is different (about 3 to 5 times smaller) from that observed in technological superconductors, but evidence is provided showing that this prefactor depends on the details of 1կ effects at the edges of superconducting grains. In 2D, the analytic flux shear calculation developed by Pruymboom in his thin-film work gives good agreement with our computational results.Visualization of Iぜ and dissipation (including movies in the 2D case) shows that in both 2D and 3D, Jc is determined by flux shear along grain boundaries. In 3D the moving fluxons are confined to the grain boundaries, and cut through stationary fluxons which pass through the grains and are almost completely straight.

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36

Haas, Tobias [Verfasser], and Guido [Akademischer Betreuer] Schneider. "Amplitude equations for Boussinesq and Ginzburg-Landau-like models / Tobias Haas ; Betreuer: Guido Schneider." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2019. http://d-nb.info/1211649709/34.

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37

Aydi, Hassen. "Vorticité dans le modèle de Ginzburg-Landau de la supraconductivité." Phd thesis, Université Paris XII Val de Marne, 2004. http://tel.archives-ouvertes.fr/tel-00297136.

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Prenant $\e=\frac{1}{\kappa}$ avec $\kappa>0$ est le paramètre de Ginzburg-Landau, ce mémoire de thèse porte sur l'étude asymptotique dans la limite $\e\ri 0$ des minimiseurs périodiques ainsi que des points critiques de l'énergie de Ginzburg-Landau.
En première partie, on prouve pour des certeins champs magnétiques appliqués $h_{ex}$ à la surface du supraconducteur de l'ordre du premier champ critique $H_{c_1}=\frac{|\log\e|}{2}$ que pour les minimiseurs périodiques de Ginzburg-Landau, le nombre des vortex par période est de l'ordre de $h_{ex}$ et leur répartition est uniforme. En outre, en prenant des champs $h_{ex}$ proches de $H_{c_1}$ de la forme $h_{ex}=H_{c_1}+f(\e)$ où $f(\e)\rightarrow +\infty$ et $f(\e)=o(|\log\e|)$, on montre que le nombre de vortex des minimiseurs périodiques par période est de l'ordre de $f(\e)$ et leur répartition est aussi uniforme.
Dans une deuxième partie, toujours dans le modèle périodique, on construit une suite de points critiques ayant des vortex répartis sur un nombre fini de lignes horizontales.
Dans une troisième partie, on construit dans le cas d'un disque une suite de points critiques telle que les vortex sont répartis sur un nombre fini de cercles concentriques de rayon strictement positif et de centre, le centre du disque. Dans le cas où il y a un seul cercle de vorticité, le rayon est bien caractérisé.
Finalement, dans un modèle de Ginzburg-Landau avec "pinning", on s'intéresse à l'étude du signe des degrés des vortex et on donne des résultats partiels indiquant que les degrés ne sont pas toujours positifs.

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Côte, Delphine. "Vortex et données non bornées pour les équations de Ginzburg-Landau paraboliques." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066002.

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Nous nous intéressons dans ce mémoire à des équations d'évolution associées aux fonctionnelles de Ginzburg-Landau, de nature parabolique. Notre but est de décrire le comportement temporel de la limite des solutions quand un petit paramètre de pénalisation tend vers 0.Dans le premier chapitre, nous retraçons de manière synthétique l'étude remarquable due à Bethuel, Orlandi et Smets sur l'équation de Ginzburg-Landau parabolique en dimension 2 : l'évolution des points vortex est gouvernée par le flot gradient de la fonctionnelle de Kirchoff-Onsager modifié par un terme de drift; elle est régulière hors des temps de collision ou de séparation de vortex ;ces phénomènes sont soumis à la conservation du degré local et à la dissipation d'énergie.Dans le second chapitre, nous considérons le problème de Cauchy pour des systèmes d'équations paraboliques semi-linéaires. Motivés par l'exemple des vortex, nous construisons, pour des nonlinéarités défocalisantes, des solutions globales de l'équation intégrale associée ayant des données initiales non bornées en espace (croissant comme exp(x^2)). Dans le cas de nonlinéarités focalisantes, nous montrons un phénomène d'explosion instantanée.Dans le troisième chapitre, nous revenons à l'équation de Ginzburg-Landau parabolique en dimension quelconque. Nous remplaçons la borne sur l'énergie de Bethuel, Orlandi et Smets, par une borne locale en espace, qui permet de traiter des configurations générales de vortex sans avoir recours aux « vortex évanescents ». Nous étendons leur analyse, et montrons des résultats de décomposition de l'énergie renormalisée, et du mouvement par courbure moyenne de la mesure d'énergie concentrée
We are interested in this thesis in evolution equations related to the Ginzburg-Landau functionals, of parabolic nature. Our goal is to describe the temporal behavior of limiting solutions as a small penalisation parameter tends to 0.In the first chapter, we retrace in a synthetic way the remarkable study by Bethuel, Orlandi and Smets on the parabolic Ginzburg-Landau equation in dimension 2 : the evolution of point vortices is governed by the gradient flow of the Kirchoff-Onsager functionnal modified by a drift term ; it is smooth away from the merging and splitting times ; these phenomenon are subject to conservation of the local degree and energy dissipation.In the second chapter, we consider the Cauchy problem for systems of semi-linear parabolic equations. Motivated by the example of the vortices, we construct, for defocusing nonlinearities, global solutions to the associated integral equation with intial data unbounded in space (allowed to grow like exp(x^2)). In the case of focusing nonlinearities, we show a phenomenon of instantaneous blow-up.In the third chapter, we go back to the parabolic Ginzburg-Landau equation. We replace the energy bound of Bethuel, Orlandi et Smets by a local-in-space bound on the energy. This allows to consider general configurations of vortices without the help of « vanishing vortices ». We extend their analysis, and show various results of decomposition of the renormalized energy, and that the concentrated energy moves according to the mean curvature flow

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39

Jefferson, Daniel Richard. "A numerical and analytical approach to turbulence in a special class of complex Ginzburg Landau equations." Thesis, Heriot-Watt University, 2002. http://hdl.handle.net/10399/412.

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Miranda, Adalberto Gomes de. "Estudo sobre a teoria de Ginzburg-Landau e o conhecimento de mapas conceituais." Universidade Federal do Amazonas, 2013. http://tede.ufam.edu.br/handle/tede/3452.

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Made available in DSpace on 2015-04-22T22:07:21Z (GMT). No. of bitstreams: 1 adalberto.pdf: 2643580 bytes, checksum: e1a556373c92d8f9719b0691629848d1 (MD5) Previous issue date: 2013-02-08
Fundação de Amparo à Pesquisa do Estado do Amazonas
The objective of this work is to present a proposal for a theoretical analysis of the theory of superconductivity together with an analysis of the Ginzburg-Landau equations in this context, in which the superconducting state is characterized by an order parameter, given by constructing a wave function Ψ (r, t) to describe the quantum behavior of particles and to show the knowledge of concept maps as a didactics tool. We will present the theoretical aspects of the phenomenon of superconductivity and its applications, and examples of conceptual maps including some models containing concepts of superconductivity. The specific objective is to use the maps as a conceptual study of physics theory in the academic, they are methodological tools to help in understanding the concepts with the interpretations, through hierarchical diagrams, shown in a conceptual framework. The research methods adopted are the development of the Ginzburg-Landau equations, the research that includes students enrolled in undergraduate courses in Physics, as individual basis and for last the implementation of a short course, with the participation of undergraduate and graduate students in physics and related areas, distributed in groups or individually to analyze the results. The survey instrument adopted for the last two methods, in order to obtain the scores for the students performance, will be a simple questionnaire, using pencil, black ballpoint pen and A4 paper, containing eleven questions in the first method and in the second method (short course) it will be ten conceptual questions (open or closed) about the concepts related to the topics provided by the instructor and finally it will be presented the analyzes of the results.
O objetivo deste trabalho é apresentar uma proposta de análise teórica da teoria da supercondutividade conjuntamente com uma análise das equações de Ginzburg-Landau neste contexto, em que um estado do supercondutor é caracterizado por um parâmetro de ordem, dado pela construção de uma função de onda Ψ(r,t) para descrever o comportamento quântico das partículas e mostrar o conhecimento de mapas conceituais como ferramenta didática. Serão apresentados os aspectos teóricos do fenômeno da supercondutividade e suas aplicações, e exemplos de mapas conceituais incluindo alguns modelos contendo conceitos da Supercondutividade. O objetivo específico é o de utilizar os mapas conceituais como um estudo da teoria Física no âmbito acadêmico, porque são instrumentos metodológicos para ajudar na compreensão dos conceitos com as interpretações, através de diagramas hierárquicos, mostrados em uma estrutura conceitual. Os métodos da pesquisa adotados são os de desenvolvimento das equações de Ginzburg-Landau, os da investigação que contarão com discentes matriculados nos cursos de graduação em Física, de forma individual e por ultimo a aplicação de um minicurso, com a participação de graduandos e graduados em Física e áreas afins, distribuídos em grupos ou individual para análise dos resultados. O instrumento de pesquisa adotado para estes dois últimos métodos, fins de obter os escores referentes ao desempenho dos discentes, será um questionário simples, utilizando lápis, caneta esferográfica preta e papel A4 contendo, no primeiro método onze questões e no segundo método (minicurso) dez questões conceituais (abertas ou fechadas) sobre os conceitos relacionados aos temas fornecidos pelo instrutor e finalmente, serão apresentados as análises dos resultados.

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41

Bochard, Pierre. "Vortex, entropies et énergies de ligne en micromagnétisme." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112119/document.

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Cette thèse traite de questions mathématiques posées par des problèmes issus du micromagnétisme ; un thème central en est les champs de vecteur de rotationnel nul et de norme 1, qu'on voit naturellement apparaître comme configurations minimisant des énergies micromagnétiques.Le premier chapitre est motivé par la question suivante : peut-on, en dimension plus grande que deux, caractériser les champs de vecteur de rotationnel nul et de norme 1 par une formulation cinétique ?Une telle formulation a d'abord été introduite en dimension 2 dans l'article \cite{Jabin_Otto_Perthame_Line_energy_2002} de Jabin, Otto et Perthame où elle apparaît naturellement dans le cadre de la minimisation d'une énergie de type Ginzburg-Landau. Ignat et De Lellis ont ensuite montré dans \cite{DeLellis_Ignat_Regularizing_2014} qu'une telle formulation cinétique caractérise les champs de rotationnel nul et de norme 1 possédant une certaine régularité en dimension 2. Le premier chapitre de cette thèse est consacré à l'étude d'une formulation cinétique similaire en dimension quelconque ; le résultat principal en est qu'en dimension strictement plus grande que 2, cette fomulation cinétique ne caractérise non plus tous les champs de rotationnel nul et de norme 1, mais seulement les champs constants ou les vortex.La caractérsation cinétique des champs de vecteur de rotationnel nul et de norme 1 en dimension 2,prouvée par De Lellis et Ignat et que nous venons de mentionner reposait sur la notion d'entropie.Ayant obtenu une formulation cinétique en dimension quelconque, il était naturel de vouloir l'exploiter un tentant d'étendre également la notion d'entropie aux dimensions supérieures à 2. C'est ce à quoi est consacré le deuxième chapitre de cette thèse ; nous y définissons en particulier une notion d'entropie en dimension quelconque. Le point central en est la caractérisation de ces entropies par un système d'\équations aux dérivées partielles, et leur description complète en dimension 3, ainsi que la preuve pour ces entropies de propriétés tout à fait semblables à celles des entropies deux dimensionnelles.Le troisième chapitre de cette thèse, qui expose les résultats d'un travail en collaboration avec Antonin Monteil, s'intéresse à la minimisation d'\'energies de type Aviles-Giga de la forme $\mathcal_f(m)=\int_f(|m^+-m^-|)$ o\`u $m$ est un champ de rotationnel nul et de norme 1 et où $J(m)$ désigne les lignes de saut de $m$. Deux questions classiques se posent pour ce type d'énergie : la solution de viscosité de l'équation eikonale est-elle un minimiseur et l'énergie est-elle semi-continue inférieurement pour une certaine topologie. Le résutat principal de cette partie est un construction, qui nous permet en particulier de répondre par la négative à ces deux questions dans les cas où $f(t)= t^p$ avec $p \in ]0,1[$ en donnant une condition nécessaire sur $f$ pour que $\mathcal_f$ soit semi-continue inférieurement.Enfin, le dernier chapitre de cette thèse est consacré à l'étude d'une variante de l'énergie de Ginzburg-Landau introduite par Béthuel, Brezis et Helein où on a remplacé la condition de bord par une pénalisation dépendant d'un paramètre. Nous y décrivons le comportement asymptotique de l'énergie minimale qui, suivant la valeur de ce paramètre, soit se comporte comme l'énergie de Ginzburg-Landau classique en privilégiant une configuration vortex, soit privilégie au contraire une configuration singulière suivant une ligne
This thesis is motivated by mathematical questions arising from micromagnetism. One would say that a central topic of this thesis is curl-free vector fields taking value into the sphere. Such fields naturally arise as minimizers of micromagnetic-type energies. The first part of this thesis is motivated by the following question : can we find a kinetic formulation caracterizing curl-free vector fields taking value into the sphere in dimension greater than 2 ? Such a formulation has been found in two dimension by Jabin, Otto and Perthame in \cite. De Lellis and Ignat used this formulation in \cite{DeLellis_Ignat_Regularizing_2014} to caracterize curl-free vector fields taking value into the sphere with a given regularity. The main result of this part is the generalization of their kinetic formulation in any dimension and the proof that if $d>2$, this formulation caracterizes only constant vector fields and vorteces, i. e. vector fields of the form $\pm \frac$. The second part of this thesis is devoted to a generalization of the notion of \textit, which plays a key role in the article of De Lellis and Ignat we talked about above. We give a definition of entropy in any dimension, and prove properties quite similar to those enjoyed by the classical two-dimensional entropy. The third part of this thesis, which is the result of a joint work with Antonin Monteil, is about the study of an Aviles-Giga type energy. The main point of this part is a necessary condition for such an energy to be lower semi continuous. We give in particular an example of energy of this type for which the viscosity solution of the eikonal equation is \textit a minimizer. The last part, finally is devoted to the study of a Ginzburg-Landau type energy where we replace the boundary condition of the classical Ginzburg-Landau energy introduced by Béthuel, Brezis and Helein by a penalization within the energy at the critical scaling depending on a parameter. The core result of this part is the description of the asymptotic of the minimal energy, which, depending on the parameter, favorizes vortices-like configuration like in the classical Ginzburg-Landau case, or configurations singular along a line

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42

Rodiac, Rémy. "Méthodes variationnelles pour des problèmes sous contrainte de degrés prescrits au bord." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1108/document.

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Cette thèse est dédiée à l'analyse mathématique de quelques problèmes variationnels motivés par le modèle de Ginzburg-Landau en théorie de la supraconductivité. Dans la première partie on étudie l'existence de solutions pour les équations de Ginzburg-Landau sans champ magnétique et avec données au bord de type semi-rigides. Ces données consistent à prescrire le module de la fonction sur le bord du domaine ainsi que son degré topologique. C'est un cas particulier de problèmes à bord libre, ou la donnée complète de la fonction sur le bord est une inconnue du problème. L'existence de solutions à ce problème n'est pas assurée. En effet la méthode directe du calcul des variations ne peut pas s'appliquer car le degré sur le bord n'est pas continu pour la convergence faible dans l'espace de Sobolev adapté. On dit que c'est un problème sans compacité. En étudiant le phénomène de "bubbling" qui apparaît dans l'étude de tels problèmes on donne des résultats d'existence et de non existence de solutions. Dans le Chapitre 1 on étudie des conditions qui permettent d'affirmer que la différence entre deux niveaux d'énergie est strictement optimale. Pour cela on adapte une technique due à Brezis-Coron. Ceci nous permet de redémontrer un résultat (précédemment obtenu par Berlaynd Rybalko et Dos Santos) d'existence de solutions stables pour les équations de Ginzburg-Landau dans des domaines multiplement connexes. Dans le Chapitre 2 on considère les applications harmoniques a valeurs dans $R^2$ avec des conditions au bord de type degrés prescrits sur un anneau. On fait un lien entre ce problème et la théorie des surfaces minimales dans $R^3$ grâce à la différentielle quadratique de Hopf. Ceci nous conduit à l'étude des surfaces minimales bordées par deux cercles dans des plans parallèles. On prouve l'existence de telles surfaces qui ne sont pas des catenoides grâce a un résultat de bifurcation. On utilise alors les résultats obtenus pour déduire des théorèmes d'existence et de non existence de minimiseurs de l'énergie de Ginzburg-Landau à degrés prescrits dans un anneau. Dans ce troisième Chapitre on obtient des résultats pour une valeur du paramètre " grand. Le Chapitre 4 a pour objet l'étude des problèmes a degrés prescrits en dimension n3. On y montre la non existence des minimiseurs de la n-énergie de Ginzburg-Landau a degrés prescrits dans un domaine simplement connexe. On étudie ensuite des points critiques de type min-max pour une énergie perturbée. La deuxième partie est consacrée a l'analyse asymptotique des solutions des équations deGinzburg-Landau lorsque " tend vers zero. Sandier et Serfaty ont étudié le comportement asymptotique des mesures de vorticité associées aux équations. Ils ont notamment trouvé des conditions critiques sur les mesures limites dans le cas des équations avec et sans champ magnétique. Nous nous intéressons alors à ces conditions critiques dans le cas sans champ magnétique. Le problème de la régularité locale des mesures limites se ramène ainsi a l'étude de la régularité des fonctions stationnaires harmoniques dont le Laplacien est une mesure. Nous montrons que localement de telles mesures sont supportées par une union de lignes appartenant à l'ensemble des zéros d'une fonction harmonique
This thesis is devoted to the mathematical analysis of some variational problems. These problem sare motivated by the Ginzburg-Landau model related to the super conductivity. In the first part we study existence of solutions of the Ginzburg-Landau equations without magnetic eld but with semi-sti boundary conditions. These conditions are obtained by prescribing the modulus of the function on the boundary of the domain along with its topological degree. This is a particular case of free boundary problems, where the function on the boundary is an unknown of the problem. Existence of solutions of that problem does not necessary hold. Indeed we can not apply the direct method of the calculus of variations since the degree on the boundaryis not continuous with respect to the weak convergence in an appropriated Sobolev space. This is problem with loss of compactness. By studying the bublling" phenomenon which come upin such problems we obtain some existence and non existence results .In Chapter 1 we study conditions under which the dierence between two energy levels is strictly optimal. In order to do that we adapt a technique due to Brezis-Coron. This allow us to recover known existence results (previously obtained by Berlyand and Rybalko and DosSantos) for stable solutions of the Ginzburg-Landau equations in multiply connected domains. In Chapter 2 we are interested in harmonic maps with values in $R^2$ with prescribed degree boundary condition in an annulus. We make a link between this problem and the minimal surface theory in $R^3$ thanks to the so-called Hopf quadratic differential. This leads us to study immersed minimal surfaces bounded by two circles in parallel planes. We prove the existence of such surfaces die rent from catenoids by using a bifurcation argument. We then apply the results obtained to deduce existence and non existence results for minimizers of the Ginzburg-Landau energy with prescribed degrees. This is done in Chapter 3 where the results are obtained for large ".Chapter 4 is devoted to prescribed degree problems in dimension n3 . We prove the non existence of minimizers of the Ginzburg-Landau energy in simply connected domains. We then study min-max critical points of a perturbed energy. The second part is devoted to the asymptotic analysis of solutions of the Ginzburg-Landau equations when "goes to zero. Sandier and Serfaty studied the asymptotic behavior of the vorticity measures associated to these equations. They derived critical conditions on the limiting measures both with and without magnetic Field. We are interested by these conditions when there is no magnetic Field. The problem of the local regularity of the limiting measures is then equivalent to the study of regularity of stationary harmonic functions whose Laplacianis a measure. We show that locally such measures are concentrated on a union of lines which belong to the zero set of an harmonic function

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43

Román, Carlos. "Analysis of singularities in elliptic equations : the Ginzburg-Landau model of superconductivity, the Lin-Ni-Takagi problem, the Keller-Segel model of chemotaxis, and conformal geometry." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066343/document.

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Cette thèse est consacrée à l'analyse des singularités apparaissant dans des équations différentielles partielles elliptiques non linéaires découlant de la physique mathématique, de la biologie mathématique, et de la géométrie conforme. Les thèmes abordés sont le modèle de supraconductivité de Ginzburg-Landau, le problème de Lin-Ni-Takagi, le modèle de Keller-Segel de la chimiotaxie, et le problème de courbure scalaire prescrite. Le modèle de Ginzburg-Landau est une description phénoménologique de la supraconductivité. Une caractéristique essentielle des supraconducteurs de type II est la présence de vortex, qui apparaissent au-dessus d'une certaine valeur de la force du champ magnétique appliqué, appelée premier champ critique. Nous nous intéressons au régime de epsilon petit, où epsilon est l'inverse du paramètre de Ginzburg-Landau (une constante du matériau). Dans ce régime, les vortex sont au premier ordre des singularités topologiques de co-dimension 2. Nous fournissons une construction quantitative par approximation de vortex en dimension trois pour l'énergie de Ginzburg-Landau, ce qui donne une approximation des lignes de vortex ainsi qu'une borne inférieure pour l'énergie, qui est optimale au premier ordre et vérifiée au niveau epsilon. En utilisant ces outils, nous analysons ensuite le comportement des minimiseurs globaux en dessous et proche du premier champ critique. Nous montrons que, en dessous de cette valeur critique, les minimiseurs de l'énergie de Ginzburg-Landau sont des configurations sans vortex et que les minimiseurs, proche de cette valeur, ont une vorticité bornée. Le problème de Lin-Ni-Takagi apparait comme l'ombre (dans la littérature anglaise ``shadow'') du système de Gierer-Meinhardt d'équations de réaction-diffusion qui modélise la formation de motifs biologiques. Ce problème est celui de trouver des solutions positives d'une équation critique dans un domaine régulier et borné de dimension trois, avec une condition de Neumann homogène au bord. Dans cette thèse, nous construisons des solutions à ce problème présentant un comportement explosif en un point du domaine, lorsqu'un certain paramètre converge vers une valeur critique. La chimiotaxie est l'influence de substances chimiques dans un environnement sur le mouvement des organismes. Le modèle de Keller-Segel pour la chimiotaxie est un système de diffusion-advection composé de deux équations paraboliques couplées. Ici, nous nous intéressons aux états stationnaires radiaux de ce système. Nous sommes alors amenés à étudier une équation critique dans la boule unité de dimension 2, avec une condition de Neumann homogène au bord. Dans cette thèse, nous construisons plusieurs familles de solutions radiales qui explosent à l'origine de la boule, et se concentrent sur le bord et/ou sur une sphère intérieure, lorsqu' un certain paramètre converge vers zéro. Enfin, nous étudions le problème de la courbure scalaire prescrite. Étant donnée une variété Riemannienne compacte de dimension n, nous voulons trouver des métriques conformes dont la courbure scalaire soit une fonction prescrite, qui dépend d'un petit paramètre. Nous supposons que cette fonction a un point critique qui satisfait une hypothèse de platitude appropriée. Nous construisons plusieurs métriques, qui explosent lorsque le paramètre converge vers zéro, avec courbure scalaire prescrite
This thesis is devoted to the analysis of singularities in nonlinear elliptic partial differential equations arising in mathematical physics, mathematical biology, and conformal geometry. The topics treated are the Ginzburg-Landau model of superconductivity, the Lin-Ni-Takagi problem, the Keller-Segel model of chemotaxis, and the prescribed scalar curvature problem. The Ginzburg-Landau model is a phenomenological description of superconductivity. An essential feature of type-II superconductors is the presence of vortices, which appear above a certain value of the strength of the applied magnetic field called the first critical field. We are interested in the regime of small epsilon, where epsilon is the inverse of the Ginzburg-Landau parameter (a material constant). In this regime, the vortices are at main order co-dimension 2 topological singularities. We provide a quantitative three-dimensional vortex approximation construction for the Ginzburg-Landau energy, which gives an approximation of vortex lines coupled to a lower bound for the energy, which is optimal to leading order and valid at the epsilon-level. By using these tools we then analyze the behavior of global minimizers below and near the first critical field. We show that below this critical value, minimizers of the Ginzburg-Landau energy are vortex-free configurations and that near this value, minimizers have bounded vorticity. The Lin-Ni-Takagi problem arises as the shadow of the Gierer-Meinhardt system of reaction-diffusion equations that models biological pattern formation. This problem is that of finding positive solutions of a critical equation in a bounded smooth three-dimensional domain, under zero Neumann boundary conditions. In this thesis, we construct solutions to this problem exhibiting single bubbling behavior at one point of the domain, as a certain parameter converges to a critical value. Chemotaxis is the influence of chemical substances in an environment on the movement of organisms. The Keller-Segel model for chemotaxis is an advection-diffusion system consisting of two coupled parabolic equations. Here, we are interested in radial steady states of this system. We are then led to study a critical equation in the two-dimensional unit ball, under zero Neumann boundary conditions. In this thesis, we construct several families of radial solutions which blow up at the origin of the ball and concentrate on the boundary and/or an interior sphere, as a certain parameter converges to zero. Finally, we study the prescribed scalar curvature problem. Given an n-dimensional compact Riemannian manifold, we are interested in finding bubbling metrics whose scalar curvature is a prescribed function, depending on a small parameter. We assume that this function has a critical point which satisfies a suitable flatness assumption. We construct several metrics, which blow-up as the parameter goes to zero, with prescribed scalar curvature

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44

Martelli, Pierre-William. "Modélisation et simulations numériques de la formation de domaines ferroélectriques dans des nanostructures 3D." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0119/document.

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Dans cette thèse, nous étudions la formation de domaines ferroélectriques dans des nanostructures, à partir d'une modélisation faisant intervenir les équations de Ginzburg-Landau et d’Électrostatique, ainsi que des conditions aux limites d'application potentielle. Dans la première partie de la thèse, les nanostructures sont constituées d'une couche ferroélectrique entièrement enclavée dans un environnement paraélectrique. Nous introduisons un modèle depuis un couplage de ces équations et élaborons, pour son investigation, un schéma numérique faisant usage d’Éléments Finis. Des simulations numériques montrent l'efficacité de ce schéma, qui permet d'établir, par exemple, l'existence de cycles d'hystérésis sous l'influence de paramètres aussi bien physiques que géométriques. Dans la seconde partie, les nanostructures sont constituées d'une couche ferroélectrique partiellement enclavée qui s'intercale entre deux couches paraélectriques. Deux modèles sont proposés à partir d'une variante du couplage réalisé dans la première partie, et se distinguent dans la prescription des conditions aux limites. Des conditions de type Neumann interviennent dans le premier modèle, pour lequel un schéma numérique aussi basé sur des approximations par Eléments Finis est introduit. Dans le second modèle, des conditions périodiques sont prises en considération ; un schéma numérique s'appuyant ici sur une hybridation des méthodes de Différences Finies et d'Eléments Finis est présenté. Les simulations numériques basées sur ces deux schémas permettent de renseigner sur les permittivités dites effectives, des nanostructures, ou encore sur la constitution des parois de domaines ferroélectriques
In this thesis, we study the formation of ferroelectric domains in nanostructures by modeling based on the Ginzburg-Landau and Electrostatics equations, together with boundary conditions that are suitable for real applications. In the first part of the thesis, the nanostructures are made up of a ferroelectric layer, fully enclosed in a paraelectric environment. We introduce a model based on the coupled system of equations and then develop, for its investigation, a numerical scheme using Finite Elements. Numerical simulations show the efficiency of this scheme, which allows us to establish, for instance, the existence of hysteresis cycles under the influence of physical or geometric parameters. In the second part, the nanostructures are made up of a partially enclosed ferroelectric layer that lies between two paraelectric layers. Two models are introduced from a variant of the coupling performed in the first part, and differ in the prescription of the boundary conditions. Neumann type conditions are prescribed in the first model, for which a numerical scheme also based on Finite Element approximations is developed. In the second model, periodic conditions are taken into account; a numerical scheme based on a combination of Finite Difference and Finite Element methods is presented. Numerical simulations from these schemes allow us, for instance, to investigate the so-called effective permittivities, of the nanostructures, or the formation of ferroelectric domain walls

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45

Metikas, Georgios. "Aspects of thermal field theory with applications to superconductivity." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312156.

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46

Duerinckx, Mitia. "Topics in the mathematics of disordered media." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/262390.

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Cette thèse est consacrée à l’étude mathématique des effets de désordre dans divers systèmes physiques. On commence par trois problèmes d’homogénéisation stochastique en lien avec des questions statiques de physique classique. Premièrement, en vue de la déduction rigoureuse de l’élasticité non-linéaire à partir de la physique statistique de réseaux de chaînes de polymères, on établit l’existence de propriétés effectives pour des matériaux hyperélastiques hétérogènes aléatoires sous des hypothèses générales de croissance. Deuxièmement, dans un cadre linéarisé simplifié, on étudie les formules de Clausius-Mossotti pour les propriétés effectives d’alliages binaires dilués: on donne la première preuve générale et rigoureuse de ces formules, ainsi qu’une extension aux ordres supérieurs. Troisièmement, encore pour des systèmes linéarisés, on propose d’étudier les déviations par rapport aux propriétés effectives et on établit la première théorie générale des fluctuations en homogénéisation stochastique. Dans la seconde partie de cette thèse, on se focalise sur la compétition entre désordre et interactions, et on étudie plus particulièrement la dynamique des vortex de Ginzburg-Landau dans des supraconducteurs 2D de type II en présence d’impuretés. Bien que la compréhension mathématique des propriétés vitreuses complexes de ces systèmes semble hors de portée, on établit rigoureusement la limite de champ moyen pour la dynamique d’un grand nombre de vortex, et on étudie l’homogénéisation de ces équations limites et leurs propriétés.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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47

Thorel, Alexandre. "Équation de diffusion généralisée pour un modèle de croissance et de dispersion d'une population incluant des comportements individuels à la frontière des divers habitats." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMLH07/document.

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Le but de ce travail est l'étude d'un problème de transmission en dynamique de population entre deux habitats juxtaposés. Dans chacun des habitats, on considère une équation aux dérivées partielles, modélisant la dispersion généralisée, formée par une combinaison linéaire du laplacien et du bilaplacien. On commence d'abord par étudier et résoudre la même équation avec diverses conditions aux limites posée dans un seul habitat. Cette étude est effectuée grâce à une formulation opérationnelle du problème: on réécrit cette EDP sous forme d'équation différentielle, posée dans un espace de Banach construit sur les espaces Lp avec 1 < p < +∞, où les coefficients sont des opérateurs linéaires non bornés. Grâce au calcul fonctionnel, à la théorie des semi-groupes analytiques et à la théorie de l'interpolation, on obtient des résultats optimaux d'existence, d'unicité et de régularité maximale de la solution classique si et seulement si les données sont dans certains espaces d'interpolation
The aim of this work is the study of a transmission problem in population dynamics between two juxtaposed habitats. In each habitat, we consider a partial differential equation, modeling the generalized dispersion, made up of a linear combination of Laplacian and Bilaplacian operators. We begin by studying and solving the same equation with various boundary conditions in a single habitat. This study is carried out using an operational formulation of the problem: we rewrite this PDE as a differential equation, set in a Banach space built on the spaces Lp with 1 < p < +∞, where the coefficients are unbounded linear operators. Thanks to functional calculus, analytic semigroup theory and interpolation theory, we obtain optimal results of existence, uniqueness and maximum regularity of the classical solution if and only if the data are in some interpolation spaces

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Salhi, Mohamed. "Etude des lasers à fibre en régime verrouillé en phase par rotation non-linéaire de la polarisation." Angers, 2004. http://www.theses.fr/2004ANGE0018.

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Les lasers à fibre dopée sont de très bons candidats pour la réalisation de lasers à impulsions courtes. En effet, les largeurs spectrales sont relativement importantes et de plus, plusieurs techniques existent pour verrouiller en phase de manière passive. Dans ce travail, nous avons étudié théoriquement un laser à fibre verrouillé en phase par la technique de rotation non linéaire de la polarisation. La configuration comprend un polariseur placé entre deux contrôleurs de polarisation dans une cavité en anneau unidirectionnelle. Le modèle développé se réduit à une équation de type Ginzburg-Landau complexe et permet d'obtenir des solutions analytiques dans le cas des régimes continu et à impulsions courtes. Le passage d'un régime à l'autre se fait en tournant les contrôleurs de polarisation. Ce modèle est en très bon accord avec les résultats obtenus avec un laser à fibre dopée ytterbium. L'étude a aussi portée sur le laser erbium ainsi que sur le laser à impulsions étirées
Rare-earth doped fibers are very good candidates to develop short-pulses lasers. Indeed, they exhibit very large optical spectra and, in addition, various methods to achieve passively mode-locking can be used. In this work, we have theoretically investigated a fiber laser passively mode-locked through nonlinear polarization rotation. The laser contains a polarizer placed between two polarization controllers in a unidirectional ring cavity. The model reduces to a complex Ginzburg-Landau equation and allows obtaining analytic solutions in the continuous or mode-lock regimes. Unstable regime is also obtained. The orientation of the polarization controllers allows switching from one regime to the other. The model is in very good agreement with the experimental results obtained in the case of the ytterbium-doped double-clad fiber laser. Both the cases of the erbium-doped and the stretched-pulse lasers have been investigated

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49

Yu, Haofeng. "A Numerical Investigation Of The Canonical Duality Method For Non-Convex Variational Problems." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/29095.

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This thesis represents a theoretical and numerical investigation of the canonical duality theory, which has been recently proposed as an alternative to the classic and direct methods for non-convex variational problems. These non-convex variational problems arise in a wide range of scientific and engineering applications, such as phase transitions, post-buckling of large deformed beam models, nonlinear field theory, and superconductivity. The numerical discretization of these non-convex variational problems leads to global minimization problems in a finite dimensional space. The primary goal of this thesis is to apply the newly developed canonical duality theory to two non-convex variational problems: a modified version of Ericksen's bar and a problem of Landau-Ginzburg type. The canonical duality theory is investigated numerically and compared with classic methods of numerical nature. Both advantages and shortcomings of the canonical duality theory are discussed. A major component of this critical numerical investigation is a careful sensitivity study of the various approaches with respect to changes in parameters, boundary conditions and initial conditions.
Ph. D.

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Odasso, Cyril. "Méthodes de couplage pour des équations stochastiques de type Navier-Stokes et Schrödinger." Phd thesis, Université Rennes 1, 2005. http://tel.archives-ouvertes.fr/tel-00011214.

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Nous nous intéresserons d'abord aux équations stochastiques de Navier-Stokes bidimensionnelles (NS), de Ginzburg-Landau Complexes (CGL) et de Schrödinger non-linéaires (NLS) munies d'un bruit blanc en temps et régulier pour la variable spatiale. En nous appuyant sur des méthodes de couplages, nous établirons le caractère exponentiellement (resp polynomialement) mélangeant de NS et CGL (resp NLS) lorseque le bruit recouvre un nombre suffisant de bas modes. Deux des innovations majeures de ces résultats sont le fait que l'on s'autorise à traiter des équations non-dissipatives telles que NLS et que l'on considère des bruits non additifs.
Dans un deuxième temps, nous considérerons les équations de Navier-Stokes stochastiques tridimensionnelles (NS3D). Nous établirons la régularité Hp et Gevrey des solutions stationnaires de NS3D et nous en déduirons des informations sur l'échelle de dissipation de Kolmogorov (K41). Puis, nous établirons le caractère exponentiellement mélangeant des solutions de NS3D lorsque le bruit est à la fois suffisament régulier et non-dégénéré.

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Dissertations / Theses on the topic 'Ginzburg-Landau equation'

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