Дисертації з теми "Systèmes désordonnés et apériodiques"
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Triozon, François. "Diffusion quantique et conductivité dans les systèmes apériodiques." Phd thesis, Université Joseph Fourier (Grenoble), 2002. http://tel.archives-ouvertes.fr/tel-00002292.
Voliotis, Dimitrios. "Contribution à l’étude des chaînes de spin quantique avec une perturbation aléatoire ou apériodique." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0253/document.
In the present thesis, the critical and off-critical behaviors of quantum spin chains in presence of a random or an aperiodic perturbation of the couplings is studied. The critical behavior of the Ising and Potts random quantum chains is known to be governed by the same Infinite-Disorder Fixed Point. We have implemented a numerical version of the Strong-Disorder Renormalization Group (SDRG) to test this prediction. We then studied the quantum random Ashkin-Teller chain by Density Matrix Renormalization Group. The phase diagram, previously obtained by SDRG, is confirmed by estimating the location of the peaks of the integrated autocorrelation times of both the spin-spin and polarization-polarization autocorrelation functions and of the disorder fluctuations of magnetization and polarization. Finally, the existence of a double-Griffiths phase is shown by a detailed study of the decay of the off-critical autocorrelation functions. As expected, a divergence of the dynamical exponent is observed along the two transition lines. In the aperiodic case, we studied both the Ising and Potts quantum chains. Using numerical SDRG, we confirmed the known analytical results for the Ising chains and proposed a new estimate of the magnetic scaling dimension.For the quantum q-state Potts chain, we estimated the magnetic scaling dimension for various aperiodic sequences and showed that it is independent of q for all sequences with a vanishing wandering exponent. However, we observed that the dynamical exponent is finite and increases with the number of states q. In contrast, for the Rudin-Shapiro sequence, the results are compatible with an Infinite-Disorder Fixed Point with a diverging dynamical exponent, equipe de renormalization
Pujol, Pierre. "Théories conformes et systèmes désordonnés." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1996. http://tel.archives-ouvertes.fr/tel-00001167.
Luck, Jean-Marc. "Propriétés critiques de systèmes désordonnés." Paris 6, 1986. http://www.theses.fr/1986PA066122.
Carvalho, Bezerra Sérgio de. "Étude asymptotique de certains systèmes désordonnés." Thesis, Nancy 1, 2007. http://www.theses.fr/2007NAN10053/document.
This thesis basically study two kinds of disorder systems. The first one the spin glasses and second one the directed polymers into a random environment. These two research themes can be solved by the utilization of the same tools. Although they are strongly different by the nature of the interactions and the geometry structure that they create. In few words, we give a summary: For the Sherrington-Kirkpatrick Spin Glasses model, we make an asymptotic study of the multiple overlap function which generalizes the typical two configuration overlap function. Afterward, we develop a central limit theorem for the partition function of a localized Sherrigton-Kirkpatrick model. At the end, we obtain a study of the partition function and a result of super-diffusivity for a brownien directed polymer model into an random gaussian environment
Tissier, Matthieu. "Une approche non perturbative de systèmes frustrés et de systèmes désordonnés." Phd thesis, Université Paris-Diderot - Paris VII, 2001. http://tel.archives-ouvertes.fr/tel-00001045.
Gueudré, Thomas. "Physique statistique des systèmes désordonnés." Thesis, Paris, Ecole normale supérieure, 2014. http://www.theses.fr/2014ENSU0009/document.
This Thesis presents several aspects of the stochastic growth, through its most paradig-matic model, the Kardar-Parisi-Zhang equation (KPZ). Albeit very simple, this equa-tion shows a rich behaviour and has been extensively studied for decades. The existenceof a new universality class is now well established, containing numerous growth modelslike the Eden model or the Polynuclear Growth Model. The KPZ equation is closelyrelated to optimisation problems (the Directed Polymer) or turbulence of uids (theBurgers equation), a feature that underlines its importance. Nonetheless, the bound-aries of this universality class are still vague. The focus of this Thesis is to probe thoselimits through various modifications of the models. It is divided in four chapters:i) First, we present theoretical tools, borrowed from integrable systems, that allowto characterize in great details the evolution of the interface. Those tools exhibitconsiderable exibility due to the large corpus of work on integrable systems, and weillustrate it by tackling the case of confined geometry (growth close to a hard wall).ii) We investigate the inuence of the disorder distribution, and more specificallythe importance of large events, with heavy-tailed distributions. Those extreme eventsstretch the interface and notably modify the main scaling exponents. The consequenceson optimization strategies in disorder landscapes are emphasized.iii) The presence of correlations in the disorder is of natural experimental interest.Although they do not impact the KPZ class, they greatly inuence the average speed ofgrowth. The latter quantity is often overlooked because it is non-universal and ratherill-defined. Nonetheless, we show that a generic optimal average speed exists in presenceof time correlations, due to a competition between exploration and exploitation.iv) Finally, we consider a set of experiments about chemical front growth in porousmedium. While this growth process is not related to KPZ in an immediate way, wepresent different tools that effciently reproduce the observations.Along that work, the consequences of each Chapter in various domains, like opti-misation strategies, turbulence, population dynamics or finance, are detailed
Bocquet, Marc. "Chaînes de Spins, Fermions de Dirac, et Systèmes Désordonnés." Phd thesis, Ecole Polytechnique X, 2000. http://tel.archives-ouvertes.fr/tel-00001560.
Schehr, Grégory. "Thermodynamique et dynamique hors d'équilibre de systèmes élastiques désordonnés." Paris 6, 2003. http://www.theses.fr/2003PA066482.
Delorme, Mathieu. "Processus stochastiques et systèmes désordonnés : autour du mouvement Brownien." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE058/document.
In this thesis, we study stochastic processes appearing in different areas of statistical physics: Firstly, fractional Brownian motion is a generalization of the well-known Brownian motion to include memory. Memory effects appear for example in complex systems and anomalous diffusion, and are difficult to treat analytically, due to the absence of the Markov property. We develop a perturbative expansion around standard Brownian motion to obtain new results for this case. We focus on observables related to extreme-value statistics, with links to mathematical objects: Levy’s arcsine laws and Pickands’ constant. Secondly, the model of elastic interfaces in disordered media is investigated. We consider the case of a Brownian random disorder force. We study avalanches, i.e. the response of the system to a kick, for which several distributions of observables are calculated analytically. To do so, the initial stochastic equation is solved using a deterministic non-linear instanton equation. Avalanche observables are characterized by power-law distributions at small-scale with universal exponents, for which we give new results
Caldara, Gaëtan. "Effets des interactions sur les systèmes 2d désordonnés." Toulouse 3, 2002. http://www.theses.fr/2002TOU30215.
Schreiber, Georg R. "Systèmes désordonnés et frustrés: modèles champ moyen et problèmes d'optimisation combinatoire." Phd thesis, Université Paris Sud - Paris XI, 1997. http://tel.archives-ouvertes.fr/tel-00000825.
Razo, López Luis Alberto. "Localisation des ondes électromagnétiques au-delà d'Anderson : rôle des corrélations, des symétries et de la topologie." Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ5013.
In a broad sense, the term wave localization refers to a phenomenon where waves are spatially confined in small regions of the space without any bounding material barriers.In this Thesis, we investigate (analytically, numerically and experimentally) different physical collective mechanisms to spatially localize, and therefore, to control electromagnetic waves. Specifically, we focus on the role of uncorrelated and correlated potentials, as well as of topological effects to achieve wave confinement. Analytical and numerical studies are accomplished in the framework of a recent approach in the modeling of Anderson localization called localization landscape theory. On the other hand, experiments are performed using a microwave platform composed by small dielectric cylinders placed inside a cavity made of two metallic plates. The cavity implements a propagative wave system, where we can efficiently control the local permittivity by means of the cylinders acting as scatterers, or as an analogic tight-binding system, where, in this case, the dielectric cylinders play the role of resonators.First, we extend the scope of the localization landscape approach to a wide class of one and two dimensional tight-binding systems in the presence of uncorrelated disorder, where localized eigenfunctions appear in both band-edges. We demonstrate how the landscape theory is able to predict accurately not only the locations, but also the energies of localized eigenfunctions in the low- and high-energy regimes. Later, by using our experimental cavity as a propagative system, we perform microwave transport experiments in two dimensional planar arrays. Experiments are carried out on a disordered lattice and on an aperiodic Vogel spiral from where we characterize the electromagnetic modal structures in real space. Our results reveals that aperiodic systems can carry a rich variety of long-lived modes—with Gaussian, exponential, and power law spatial decays—which are able to survive even in a three-dimensional environment. This is supported by different transport quantities such as the density of states, the characteristic decay time, and the Thouless conductance that are also experimentally accessible. On the contrary, we show that the eigenstates in traditional disordered media are always limited to exponential radial decays with leaking features beyond two-dimensions.Finally, we use the experimental tight-binding configuration to investigate the propagation of topological helical states. Particularly, we experimentally analyze a set of honeycomb-like structures built using a triangular lattice with an hexagonal unit cell, which are characterized by the Z_2 topological invariant. By recovering the modal structure in real space and the density of states, our results reveal the possibility to open a topological gap, dwelt by edge states that lives in the border of the structure.We demonstrate the unidirectional counterpropagative features of such helical edge states.Taken together, our results demonstrate that it is possible to model, control and localize electromagnetic waves not only within, but beyond Anderson's conception. Thanks to the crossroads we have taken, we have mapped out an itinerary that brings us closer to the main avenue leading perhaps to Anderson localization of three dimensional electromagnetic waves
Pautrat, Alain. "Etude des réseaux de vortex supraconducteurs et de systèmes électroniques désordonnés." Habilitation à diriger des recherches, Université de Caen, 2009. http://tel.archives-ouvertes.fr/tel-00431683.
Van, Den Berg Tineke. "Conductivité de spin et effets magnétiques dans les systèmes quantiques désordonnés." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4812/document.
Spintronics is a research area that is concerned with the storage and transfer of information by means of electron spins. In the first part we investigated the intrinsic spin Hall effect in the presence of disordered magnetic impurities in a paramagnetic state in a two dimensional electron gas with Rashba spin-orbit coupling. In the presence of weak magnetic disorder the spin Hall conductivity stays close to its universal (clean system) value, as shown by analytical linear response calculations and numerical simulations. Heavy spin conductivity fluctuations are observed, that increase with disorder strength. To investigate the spreading of a wavepacket on a lattice we measure the wavepacket width, the inverse participation ratio and the (2)-fractal dimension. It is shown the system undergoes a localization transition at a critical disorder strength. In the localized regime the local density of states is not uniform anymore. An anti-ferromagnetic correlation between electron spins and impurity magnetic moments is observed. Beyond the localization transition the spin conductivity increases significantly. The first quantum (Cooperon) corrections in the linear response formalism are shown to contribute positively to the spin Hall conductivity. In the second part the double exchange Hubbard model for correlated electron systems is studied using dynamical mean field theory (DMFT) with the non-crossing approximation (NCA). Around quarter filling an orbital polaron is observed, numerically and in an effective Hamiltonian. Double exchange in dilute magnetic semiconductors is studied using the coherent potential approximation (CPA)
Van, Den Berg Tineke. "Conductivité de spin et effets magnétiques dans les systèmes quantiques désordonnés." Electronic Thesis or Diss., Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4812.
Spintronics is a research area that is concerned with the storage and transfer of information by means of electron spins. In the first part we investigated the intrinsic spin Hall effect in the presence of disordered magnetic impurities in a paramagnetic state in a two dimensional electron gas with Rashba spin-orbit coupling. In the presence of weak magnetic disorder the spin Hall conductivity stays close to its universal (clean system) value, as shown by analytical linear response calculations and numerical simulations. Heavy spin conductivity fluctuations are observed, that increase with disorder strength. To investigate the spreading of a wavepacket on a lattice we measure the wavepacket width, the inverse participation ratio and the (2)-fractal dimension. It is shown the system undergoes a localization transition at a critical disorder strength. In the localized regime the local density of states is not uniform anymore. An anti-ferromagnetic correlation between electron spins and impurity magnetic moments is observed. Beyond the localization transition the spin conductivity increases significantly. The first quantum (Cooperon) corrections in the linear response formalism are shown to contribute positively to the spin Hall conductivity. In the second part the double exchange Hubbard model for correlated electron systems is studied using dynamical mean field theory (DMFT) with the non-crossing approximation (NCA). Around quarter filling an orbital polaron is observed, numerically and in an effective Hamiltonian. Double exchange in dilute magnetic semiconductors is studied using the coherent potential approximation (CPA)
Aliste, Prieto José Eduardo. "Contribution à l'étude des pavages apériodiques : théorie de translation et propriétés statistiques." Nice, 2009. http://www.theses.fr/2009NICE4033.
Sciolla, Bruno. "Dynamique quantique hors-équilibre et systèmes désordonnés pour des atomes ultrafroids bosoniques." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00734641.
Girard, Guillaume. "Caractérisation structurale de systèmes désordonnés par RMN de l’état solide et calculs DFT." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10081.
The combination of solid-state NMR spectroscopy with GIAO/GIPAW-DFT calculations is nowadays a well-established method to characterize the atomic structure of simple molecular and crystalline compounds. The present work is dedicated to the application of this methodology to more complex systems, in particular those with local disorder. In a first part, this manuscript is dedicated to the structural characterization of niobiophosphate based materials by 31P/93Nb solid-state NMR and DFT-GIPAW calculations. The cationic disorder of one of these phases has been identified and characterized by the use of a combinatory approach associating 31P solid-state NMR and DFT-GIPAW calculations. In parallel, a new methodology combining 17O solid-state NMR and DFT-GIAO calculations has been proposed in order to characterize the structure of one oxo-tungsten based precatalyst supported on amorphous silica. This approach was initially validated by studying molecular oxo-tungsten based molecular compounds. The 17O-NMR response of each oxo group is, in fact, specific to the studied compound and the related anisotropic NMR parameters can be reproduced with high accuracy by DFT-GIAO calculation. Finally, this methodology allowed us to verify the nature and structure of the supported species by taking into account different grafting pathways
Romain, Vasseur. "Indecomposabilité dans les théories des champs et applications aux systèmes désordonnés et aux problèmes géométriques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00876155.
Dubouchet, Thomas. "Spectroscopie locale à basse température dans des systèmes supraconducteurs désordonnés." Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENY036.
This thesis presents a study combining tunneling spectroscopy, point-contact Andreev spectroscopy and electronic transport on disordered superconducting indium oxide samples. Transport measurements reveal a diverging resistivity from room temperature shortcut by superconductivity at low temperature. This behavior shows that our samples are in the vicinity of the metal-insulator Anderson transition. Tunneling spectroscopy highlights a rather unusual superconducting state with a pseudogap regime above the critical temperature. It evolves at low temperature into an inhomogeneous system composed of both superconducting Cooper pairs and Cooper pairs without phase coherence, localized by the disorder. Comparison between different samples shows that incoherent Cooper pairs proliferate with increasing level of disorder, what indicates that superconductor-insulator transition in indium oxide is governed by the progressive localization of Cooper pairs. Besides, using our STM, we have continuously analyzed the local conductance between tunneling regime and contact regime. Andreev spectroscopy thus reveals a new energy scale related to the superconducting phase coherence and independent from spatial fluctuations of the density of states measured in tunneling regime. This shows that disorder induces a dichotomy between the pairing energy characterizing the binding of electrons into pairs and the coherence energy specific to macroscopic superconductivity
Dubouchet, Thomas. "Spectroscopie locale à basse température dans des systèmes supraconducteurs désordonnés." Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00576226.
Hainaut, Clément. "Effets des symétries sur la localisation dans des systèmes quantiques désordonnés." Electronic Thesis or Diss., Lille 1, 2017. http://www.theses.fr/2017LIL10082.
In this thesis, we use the Kicked Rotor, paradigm of quantum chaos, to study new physical aspects of disordered systems.We thus present the first experimental observation with atomic matter wave of a phenomenon directly linked to weak localization which is the Enhanced Return to the Origin. We show that this effect can be used as a tool to measure accuratly the decoherence in the system. We present a novel, outstandingly simple, experimental method to control symmetry properties of the Kicked Rotor. This allows us to study a disordered system in presence of a non-trivial artificial Aharonov-Bohm flux in a synthetic dimension. This gives us the opportunity to break the time reversal symmetry and then to study the physics of Anderson localization in two different symmetry classes : the orthogonal class and the unitary class. We have investigated the effect of this symmetry breaking on physical properties of 1D disordered systems by looking two signatures of quantum transport. We observe thus experimentally, for the first time, the Coherent Forward Scattering effect, predicted recently and which represents a novel genuine signature of Anderson localization. We show its distinctive signatures and a good agreement with theoretical predictions. Finally, we realise the first experimental measurements of the (G) scaling function, characteristic of transport in disordered medium, in two symmetry classes and we demonstrate their universality
Bitane, Rehab. "Transport et Fluctuations de Densité dans les Systèmes Désordonnés: Appliations à la Dispersion Atmophérique." Phd thesis, Université Nice Sophia Antipolis, 2012. http://tel.archives-ouvertes.fr/tel-00944511.
Hainaut, Clément. "Effets des symétries sur la localisation dans des systèmes quantiques désordonnés." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10082/document.
In this thesis, we use the Kicked Rotor, paradigm of quantum chaos, to study new physical aspects of disordered systems.We thus present the first experimental observation with atomic matter wave of a phenomenon directly linked to weak localization which is the Enhanced Return to the Origin. We show that this effect can be used as a tool to measure accuratly the decoherence in the system. We present a novel, outstandingly simple, experimental method to control symmetry properties of the Kicked Rotor. This allows us to study a disordered system in presence of a non-trivial artificial Aharonov-Bohm flux in a synthetic dimension. This gives us the opportunity to break the time reversal symmetry and then to study the physics of Anderson localization in two different symmetry classes : the orthogonal class and the unitary class. We have investigated the effect of this symmetry breaking on physical properties of 1D disordered systems by looking two signatures of quantum transport. We observe thus experimentally, for the first time, the Coherent Forward Scattering effect, predicted recently and which represents a novel genuine signature of Anderson localization. We show its distinctive signatures and a good agreement with theoretical predictions. Finally, we realise the first experimental measurements of the (G) scaling function, characteristic of transport in disordered medium, in two symmetry classes and we demonstrate their universality
Couëdo, François. "Transitions de phase quantiques dans les systèmes désordonnés de basse dimension." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00990782.
Chatelain, Christophe. "Modèles de Potts désordonnés et hors de l'équilibre." Habilitation à diriger des recherches, Université de Lorraine, 2012. http://tel.archives-ouvertes.fr/tel-00959733.
Hagendorf, Christian. "Evolutions de Schramm-Loewner et théories conformes : deux exemples de systèmes désordonnés de basse dimension." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00422366.
Le sujet de la seconde partie est l'étude de deux exemples de systèmes désordonnés de basse dimension. D'un coté nous établissons les propriétés de localisation et spectrales d'un hamiltonien aléatoire unidimensionnel qui interpole entre les cas du modèle de Halperin et le modèle supersymétrique désordonné. Un lien avec la diffusion unidimensionnelle dans un potentiel aléatoire permet d'étudier la modification de la dynamique ultra-lente de Sinai en présence d'absorbeurs. De l'autre côté nous analysons la transition vitreuse d'ARN pour des séquences aléatoires à l'aide de la théorie des champs de Lässig-Wiese-David. L'application au cas d'ARN soumis à une force extérieure conduit à la prédiction de la caractéristique force-extension pour des séquences hétérogènes. L'étude de la phase vitreuse nous amène à considérer un modèle hiérarchique combinatoire dont nous déterminons les exposants et lois d'échelle exactes ainsi que les corrections de taille finie.
Vetel, Jérôme. "Dynamique des systèmes magnétiques désordonnés de type Ising Fe0. 35Mg0. 65Br2 et Fe0. 8Mg0. 2Cl2." Toulouse, INSA, 1990. http://www.theses.fr/1990ISAT0005.
Nadal, Jean-Pierre. "Deux applications de la physique des systèmes désordonnés : croissance de structures et réseaux de neurones." Paris 11, 1987. http://www.theses.fr/1987PA112029.
Mayou, Didier. "Contribution à l'étude de la structure électronique et du transport dans les systèmes métalliques désordonnés." Grenoble 1, 1987. http://www.theses.fr/1987GRE10167.
Gambetti-Césare, Elise. "Effet de corrélations électroniques et du spin sur les courants permanents dans des anneaux unidimensionnels désordonnés." Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/GAMBETTI-CESARE_Elise_2004.pdf.
Boué, Laurent. "Vers une physique statistique du pliage et du froissage de structures élastiques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00391409.
Goetschy, Arthur. "Lumière dans les milieux atomiques désordonnés : théorie des matrices euclidiennes et lasers aléatoires." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00676988.
El, Yamani El Mustapha. "Étude de certaines propriétés de systèmes spinelles magnétiquement désordonnés et comparaison au comportement des petites particules." Paris 11, 1988. http://www.theses.fr/1988PA112221.
Anfray, Valentin. "Étude numérique du point critique de systèmes quantiques de spin désordonnés en dimensions élevées." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0127.
Several random quantum spin models have been numerically studied in dimension D>1 by Strong Disorder Renormalisation Group (SDRG). We have implemented an efficient algorithm to be able to consider a system with up to a billion spins independently of its spatial dimension. Critical properties of the 2D and 3D random quantum Potts model with q=2,3,5,10,20 and 50 states are shown to be governed by an infinite disorder fixed point. We have computed the correlation-length exponent u, the magnetization exponent d_f and the energy gap exponent psi. Using finite-size scaling and taking into account finite-size corrections, critical properties of the Potts model are shown to be q-independent. Random quantum Clock models with q=2,3,5,8 and 10 states have been also studied in 2D and 3D. A minimum amount of initial disorder strength is required to flow to an infinite disorder fixed point. Despite large error bars on psi exponent, our estimates for the critical exponents u and psi for all q are compatible with those of the random transverse-field Ising model. Our estimates for the critical exponent d_f are incompatible within error bar but very close. Lastly, the tricritical point of the random quantum Ashkin-Teller model has been studied in dimension two and three. We have shown that the correlation-length exponent associated with one of the two unstable directions does not belong to the university class of the random transverse-field Ising model
Cherrier, Raphaël. "Etude de systèmes de spins complexes ou désordonnés : analogies avec la transition vitreuse structurelle." Toulouse 3, 2003. http://www.theses.fr/2003TOU30136.
Cherrier, Raphaël. "Étude de systèmes de spins complexes ou désordonnés : analogies avec la transition vitreuse structurelle." Phd thesis, Université Paul Sabatier - Toulouse III, 2003. http://tel.archives-ouvertes.fr/tel-00840704.
Sinton, Antoine. "Modèles probabilistes avec structure spatiale en physique statistique et en informatique." Paris 6, 2009. http://www.theses.fr/2009PA066690.
Mari, Romain. "TRANSITION VITREUSE ET TRANSITION DE BLOCAGE: LES SOLIDES DÉSORDONNÉS ENTRE CHAMP MOYEN ET DIMENSION FINIE." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://pastel.archives-ouvertes.fr/pastel-00601408.
Berche, Pierre-Emmanuel. "Systèmes modèles et systèmes magnétiques : étude par simulations Monte Carlo." Habilitation à diriger des recherches, Université de Rouen, 2009. http://tel.archives-ouvertes.fr/tel-00437483.
Correia, Sebastiao. "Diffusion multiple dans les systèmes désordonnés composés de diffuseurs de taille finie et approche du groupe de renormalisation pour la description des systèmes d'électrons en interaction." Phd thesis, Université Louis Pasteur - Strasbourg I, 2000. http://tel.archives-ouvertes.fr/tel-00001525.
d'un électron dans des systèmes désordonnés sont étudiées au moyen
d'un développement perturbatif utilisant la série de Watson.
L'utilisation de potentiels de taille finie répartis de façon
aléatoire pour modéliser le désordre nécessite l'introduction de
matrices de diffusion hors couche d'énergie, qui permettent ensuite de
calculer analytiquement chaque élément de la série de Watson. Des
corrections au libre parcours moyen élastique de Boltzmann, en
dimensions 2 et 3, sont obtenues à l'aide de la moyenne d'ensemble du
propagateur de l'électron. La taille du diffuseur y joue un rôle
important.
La resommation exacte de la série de Watson sous forme matricielle
permet une étude numérique de la section efficace totale de diffusion
du système désordonné. Celle-ci montre un comportement inattendu lors
du passage du régime balistique au régime diffusif.
La deuxième partie concerne le transport d'électrons en interaction
dans les systèmes désordonnés. Le désordre y est modélisé par un
champ d'impuretés statiques. L'utilisation d'outils de la théorie des
champs permet d'envisager une approche non perturbative de ces
systèmes désordonnés dans lesquels l'interaction entre électrons peut
être à l'origine d'une transition entre le régime métallique et le régime
isolant.
Une nouvelle approche s'inspirant du groupe de renormalisation est
ensuite appliquée au calcul d'équations de flot décrivant l'évolution
des constantes de couplage d'un système d'électrons en interaction.
L'approximation à l'ordre d'une boucle permet de vérifier que ces
équations de flot conduisent aux résultats donnés par la théorie des
perturbations (RPA).
Lesueur, Jérôme. "Transition métal-isolant dans les systèmes désordonnés : étude de Al x Ge ₁ -x ultra trempé (conductivité, effet tunnel, supraconductivité)." Paris 11, 1985. http://www.theses.fr/1985PA112085.
This thesis is devoted to the study of the Mott-Anderson transition in amorphous quench-condensed (5 K) AlₓGe₁₋ₓ mixtures and in situ measurements down to 0,25 K. At xc ≈ 0,5 this system shows a Metal-Insulator Transition, superconductivity disappears and the one particule density of states at the Fermi level breaks down (as the tunneling conductivity) because of the enhancement of Coulomb interactions with disorder. The Metal insulator Transition is also obtained with similar behaviour by weak annealing (20 K to 200 K) of metallic samples initially close to the transition (0,55 ≥ x ≥ 0,5). These experiments give a good illustration of the scaling theories of localization and show the crucial part of the Coulomb repulsion near the transition as the microscopic nature of disorder in such systems
Fillaux, Clara. "Etude structurale et vibrationnelle du chlorure de zinc à hautes pressions et hautes températures." Paris 6, 2004. https://tel.archives-ouvertes.fr/tel-00007985.
Bouzerar, Richard. "Théorie pour les systèmes désordonnés de spins localisés en interaction avec des porteurs itinérants : les semiconducteurs magnétiques dilués." Phd thesis, Université de Picardie Jules Verne, 2008. http://tel.archives-ouvertes.fr/tel-00367282.
Sá, Leandro de. "Etude des propriétés des systèmes désordonnés à basses températures : mesures de chaleur spécifique dans des quartz irradiés aux neutrons." Grenoble 1, 1987. http://www.theses.fr/1987GRE10095.
Caure, Hélianthe. "Canons rythmiques et pavages modulaires." Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066126.
This thesis is a contribution to the study of modulo p tiling. Many mathematical and computational tools were used for the study of rhythmic tiling canons. Recent research has mainly focused in finding tiling without inner periodicity, being called Vuza canons. Those canons are a constructive basis for all rhythmic tiling canons, however, they are really difficult to obtain. Best current method is a brut force exploration that, despite a few recent enhancements, is exponential. Many technics have been used, hoping to understand Vuza canons better or to generate them faster. Hence, this thesis presents a completely new way to study aperiodic tiling
Poquet, Christophe. "MODÈLES STOCHASTIQUES INTERAGISSANTS : SYNCHRONISATION ET RÉDUCTION À UN SYSTÈME DE PHASES." Phd thesis, Université Paris-Diderot - Paris VII, 2013. http://tel.archives-ouvertes.fr/tel-00966053.
Luçon, Eric. "Oscillateurs couplés, désordre et synchronisation." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00709998.
Caure, Hélianthe. "Canons rythmiques et pavages modulaires." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066126/document.
This thesis is a contribution to the study of modulo p tiling. Many mathematical and computational tools were used for the study of rhythmic tiling canons. Recent research has mainly focused in finding tiling without inner periodicity, being called Vuza canons. Those canons are a constructive basis for all rhythmic tiling canons, however, they are really difficult to obtain. Best current method is a brut force exploration that, despite a few recent enhancements, is exponential. Many technics have been used, hoping to understand Vuza canons better or to generate them faster. Hence, this thesis presents a completely new way to study aperiodic tiling