Teses / dissertações sobre o tema "Disordered and aperiodic systems"
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Karevski, Dragi. "Ising Quantum Chains". Habilitation à diriger des recherches, Université Henri Poincaré - Nancy I, 2005. http://tel.archives-ouvertes.fr/hal-00113500.
Texto completo da fonteVieira, Andre de Pinho. "Efeitos de desordem ou aperiodicidade sobre o comportamento de sistemas magnéticos". Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-23022012-155648/.
Texto completo da fonteWe consider effects of disorder or aperiodicity on three different magnetic systems. First, we present a phenomenological model to describe the thermal dependence of the dilution-induced remanent magnetization in a class of quasi-one-dimensional antiferromagnets. The model treats correlations along the dominant direction in an exact way, while including the remaining inte-. i ractions via an effective field. Then, we use a self-consistent Bethe-Peierls ~ j .. approximation to gauge the effects of a random crystal field on the phase diagram of a mixed-spin Ising mode!. We show that disorder may have profound effects on the multicritical behavior associated with the uniform limit of the mo de!. Finally, we study effects of random or aperiodic interactions on the behavior of the quantum XX chain at low temperatures, by performing numerical calculations based on a mapping of the system onto a free-fermion mo de!. . We present evidence that, at zero temperature, there exists a single, universal fixed-point, associated with a random-singlet phase, which governs the behavior of the model in the presence of disordered interactions. In the case of aperiodic interactions, our results are consistent with renormalizationgroup predictions, indicating, for a certain class of substitution sequences, a behavior similar to the one induced by disorder.
Bishnani, Zahir. "Safety criteria for aperiodic dynamical systems". Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/57617/.
Texto completo da fonteLenz, Daniel. "Aspects of aperiodic order: spectral theory via dynamical systems". Doctoral thesis, [S.l.] : [s.n.], 2005. http://archiv.tu-chemnitz.de/pub/2005/0079.
Texto completo da fonteGao, Yulong. "Stochastic Invariance and Aperiodic Control for Uncertain Constrained Systems". Licentiate thesis, KTH, Reglerteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-236072.
Texto completo da fonteQC 20181016
Motakpalli, Sankalpanand. "Aperiodic Job Handling in Cache-Based Real-Time Systems". OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1474.
Texto completo da fonteVispa, Alessandro. "Dynamics of disordered systems". Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404444.
Texto completo da fonteLos sistemas desordenados son ubicuos en la naturaleza y su estudio es complicado y con frecuencia conduce a resultados controvertidos. En cualquier caso, el papel importante de este tipo de sistemas en aplicaciones científicas y tecnológicas no debe ser ignorada. Las propiedades características de tales sistemas parecen estar impulsadas por una característica fundamental, los grados de libertad. Aunque muchos problemas siguen siendo materia de debate, el desafío planteado en las últimas décadas en el entendimiento del impacto del desorden en el comportamiento físico de los materiales es de considerable interés científico. Una descripción exacta de una fase desordenada no es posible, ya que es un problema de muchos cuerpos difícil de modelar. Sin embargo, para algunos materiales, es posible, tras el enfriamiento, conservar la estructura desordenada del líquido con un estado de alta regularidad. Por lo tanto, para los denominados glass-formers, es posible congelar algunos grados de libertad obteniendo un vidrio que presenta la irregularidad de un líquido con la alta viscosidad de un sólido por debajo de la temperatura de fusión Tm. El objetivo de la presente tesis doctoral es presentar nuestra comprensión del desorden en los enfoques experimentales relacionados utilizando tres diferentes compuestos puros: dos cristales de plástico (1-Chloroadamantane y Freon113) y un líquido (Glycerol). Para entender el comportamiento de este tipo de materiales se han utilizado scattering de neutrones y espectroscopía dieléctrica. Estas dos técnicas nos permiten investigar la dinámica de las fases desordenadas en una escala de tiempo de picosegundos. Por otra parte, dada la complejidad de estas fases desordenadas, análisis de datos y la selección del modelo se han realizado con un enfoque bayesiano que proporciona una sólida base estadística basada sobre las funciones de distribución de probabilidad. Tales métodos se han aplicado al estudio de la dinámica de los compuestos antes mencionados con el fin de dar una explicación de algunas preguntas abiertas: el origen microscópico de la transición plástico-plástico en 1-chloroadamantane (C10H15Cl), la alta fragilidad y la correlación entre la fragilidad cinética y termodinámica en freon113 (Cl2FC-CClF2) y la dinámica, acompañada por una robusta selección de modelo, de uno de los compuestos más estudiados, glycerol (C3H8O3). Los resultados, presentados en este trabajo de tesis, representan un pequeño paso para una comprensión más profunda de la dinámica de las fases desordenadas, dando una base para futuras investigaciones.
Gorokhov, Denis A. "Dynamics of disordered systems /". [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13070.
Texto completo da fonteHashimoto, Kazumune. "Distributed Aperiodic Model Predictive Control for perturbed multi-agent systems". Thesis, KTH, Reglerteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-138441.
Texto completo da fonteRomanini, Michela. "Relaxation dynamics in disordered systems". Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/317384.
Texto completo da fonteLa naturaleza de la transición vítrea es un problema fundamental y aún no resuelto de la física de la materia condensada. Muchos líquidos pueden ser superenfriados por debajo de su temperatura de fusión sin que cristalicen, es decir, sin que adquieran orden traslacional y orientacional. Cuando la temperatura de un líquido superenfriado baja, el tiempo característico de los movimientos moleculares, llamado tiempo de relajación, aumenta hasta llegar a tiempos comparables con el tiempo característico de los experimentos y de la observación humana. Esto ocurre a una temperatura llamada temperatura de transición vítrea y lleva a un estado de non-equilibrio del material llamado ¿vidrio estructural¿, en el que la ausencia de orden de largo alcance típica del estado líquido se combina con las propiedades elásticas propias de un sólido ordenado. Las transiciones vítreas se pueden observar también en sistemas caracterizados por desorden exclusivamente orientacional, como en los cristales orientacionalmente desordenados (OD) o cristales plásticos. Estos son sólidos traslacionalmente ordenados en los que las moléculas tienen movimientos de reorientación alrededor de sus centros de masa, que están fijos. Superenfriando un cristal OD se obtiene un ¿vidrio orientacional¿ en el cual este desorden orientacional está congelado. El proceso dinámico más importante que caracteriza los materiales moleculares que forman vidrios estructurales u orientacionales es el movimiento cooperativo de las moléculas conocido como relajación primaria. Su congelamiento marca la transición al estado vítreo caracterizado por un desorden estático. La diferencia principal entre los vidrios orientacionales y estructurales es que en los primeros el congelamiento involucra sólo los grados de libertad de rotación, mientras que en los segundos todos los seis grados de libertad moleculares (orientacionales y traslacionales) están congelados. Por tanto, los vidrios orientacionales son sistemas con menos grados de libertad respecto los vidrios estructurales y pueden considerarse como sistemas modelo para investigar la transición vítrea, ya que además muchas fases OD están caracterizadas por redes cristalinas de alta simetría. Además de la relajación primaria, existen también relajaciones secundarias caracterizadas por tiempos de relajación más cortos con respecto al proceso primario. Estas relajaciones secundarias pueden tener diferentes orígenes: por ejemplo, pueden ser debidas a fluctuaciones de la conformación molecular o a vibraciones de enlaces intramoleculares; en muchos casos se observa una relajación secundaria que es considerada como la precursora del proceso primario (relajación Johari-Goldstein). Esta tesis está enfocada en el estudio de los efectos de la presión y de la temperatura sobre la dinámica de algunos compuestos puros y mezclas binarias, los cuales forman vidrios estructurales u orientacionales. Se presenta un estudio comparativo entre dos vidrios estructurales (ternidazole y la mezcla de m-fluoroanilina con m-xileno), un cristal plástico binario (formado por neopenthyl alcohol y neopentyl glycol), y dos materiales que presentan desorden estadístico (2-adamantanona y pentacloronitrobenceno). En todos los casos se observa una relajación primaria asociada a los movimientos colectivos de las moléculas y en la mayoría de los casos se observa también relajaciones secundarias. Para cada material se analiza la dependencia de diferentes relajaciones con la temperatura y con la presión y se discute el origen de los procesos secundarios. Uno de los resultados importantes de la tesis es que en sistemas con desorden de baja dimensionalidad, pueden aparecer relajaciones secundarias que obecen a patrones similares a las encontradas en vidrios estructurales
Rodgers, Geoffrey John. "Topics in disordered systems theory". Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329087.
Texto completo da fonteSobiesierski, Z. "Optical spectroscopy of disordered systems". Thesis, University of Exeter, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374944.
Texto completo da fonteNahm, In Hyun. "Two dimensional disordered electron systems". Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330179.
Texto completo da fonteScheffler, Falk. "Spin dynamics in disordered systems". Konstanz Hartung-Gorre, 2006. http://d-nb.info/990499073/04.
Texto completo da fonteSales, Pardo Marta. "Large Scale Excitations in Disordered Systems". Doctoral thesis, Universitat de Barcelona, 2002. http://hdl.handle.net/10803/1786.
Texto completo da fonteThe existence of these large excitations brings about large fluctuations of the order parameter, and we have shown in these theses that this feature can be exploited to study the transition of any spin glass model. Moreover, we have shown that the information about these excitations can be extracted from the statistics of the lowest lying excitations. This is because due to the random nature of spin glasses, the physics obtained from averaging over the whole spectrum of excitations of an infinite sample is equivalent to averaging over many finite systems where only the ground state and the first excitation are considered. The novelty of this approach is that we do not need to make any assumption on what are typical excitations like because we can compute them exactly using numerical methods. Finally, we have investigated the dynamics and more specifically the link between the problem of chaos and the rejuvenation phenomena observed experimentally. Rejuvenation means that when lowering the temperature the aging process restarts again from scratch. This is potentially linked with the chaos assumption which states that equilibrium configurations at two different properties are not correlated. Chaos is a large scale phenomenon possible if entropy fluctuations are large. However, in this thesis we have shown that the response to temperature changes can be large in the absence of chaos close to a localization transition where the Boltzmann weight condenses in a few states. This has been observed in simulation of the Sinai model in which this localization is realized dynamically. In this model, since at low temperatures the system gets trapped in the very deep states, the dynamics is only local, so that only small excitations contribute to the rejuvenation signal that we have been able to observe. Thus, in agreement with the hierarchical picture, rejuvenation is possible even in the absence of chaos and reflects the start of the aging process of small length scales.
Castellana, Michele. "The renormalization group for disordered systems". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00694469.
Texto completo da fonteChen, Leiming. "Tilt phase transitions in disordered systems /". view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1251884301&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
Texto completo da fonteTypescript. Includes vita and abstract. Includes bibliographical references (leaves 126-128). Also available for download via the World Wide Web; free to University of Oregon users.
Meier, Hannes. "Superfluid Phase Transitions in Disordered Systems". Licentiate thesis, KTH, Statistisk fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50051.
Texto completo da fonteQC 20111206
Passingham, Catherine. "The characterization of some disordered systems". Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236406.
Texto completo da fonteRussell, Matthew. "Transport processes in spatially disordered systems". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/transport-processes-in-spatially-disordered-systems(c4d3e5f6-681e-4403-bb47-65de4a9b2c5a).html.
Texto completo da fonteFerone, Raffaello. "Thermoelectric transport in disordered mesoscopic systems". Université Joseph Fourier (Grenoble), 2006. http://www.theses.fr/2006GRE10036.
Texto completo da fonteLa théorie de Landau des liquides de Fermi prévoit que la charge et la chaleur sont transportées par les mêmes objets: les quasi-particules fermionics de Landau. De façon très général, ceci est vrai, si l'écrantage parmi les particules dans le système est assez fort pour pouvoir continuer à considérer le système comme composé de particules indépendantes. C'est le cas, par exemple, pour la mer d'électrons dans un métal ordinaire. L'existence d'un même responsable pour le transport de la charge et de la chaleur est exprimé par la lois de Wiedemann-Franz (WF) qui affirme que le rapport entre la conductivité thermique et électrique dépend de la température par une constante qui est plus au moins la même pour plusieurs métaux. La constante de proportionnalité est appelé nombre de Lorenz. Que se passe-t-il si les conditions concernant l'écrantage que nous avons mentionnées ne sont plus satisfaites, comme par exemple dans les systèmes à dimensionalité réduite, ou des système à basse densité électronique ? Le travail de thèse est divisé en deux parties. Dans la première partie, nous avons étudié le transport thermique et électrique dans un fil quantique désordonné; dans la deuxième, l'influence des fluctuations supraconductives sur la conductivité thermique dans un métal granulaire
Kropf, Chahan [Verfasser], e Andreas [Akademischer Betreuer] Buchleitner. "Effective dynamics of disordered quantum systems". Freiburg : Universität, 2017. http://d-nb.info/1138922528/34.
Texto completo da fonteWoo, Jung Min. "Two mathematical problems in disordered systems". Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289124.
Texto completo da fonteUrbani, Pierfrancesco. "Theory of fluctuations in disordered systems". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112019.
Texto completo da fonteIn this thesis we have studied many aspects of the physics of disordered and glassy systems. The first part of the work is about the theory of dynamical fluctuations in the beta regime. When a system undergoes a dynamical arrest, it can be studied by introducing an appropriate dynamical correlation function that plays the role of the order parameter of the transition. To understand the collective effects underlying the glass transition we have studied the fluctuations of the order parameter on a time scale where the system is relaxed in a typical metastable glassy state. To do this we have seen that coming from the glass phase the system develops critical fluctuations with a diverging correlation length at the mean field level. We have thus derived an effective field theory by focusing only on them. This field theory can be used firstly to derive the mode-coupling exponent parameter that controls the relaxation of the dynamical correlation function when the system relaxes in a metastable glassy state. Moreover we can give a Ginzburg Criterion that can be used to determine the region of validity of the Gaussian approximation. These considerations are valid in the beta regime. To clarify what happens in the alpha regime we have studied a quasi-equilibrium construction, called Boltzmann-Pseudodynamics, recently introduced in order to describe with static techniques the long time regime of glassy dynamics. We have extended this formalism to structural glasses by producing a new set of dynamical equations. We have done this in the simplest approximation scheme that is called Hypernetted Chain. Two results have been obtained : firstly, we have computed the mode-coupling exponent parameter and we have shown that it coincides with the one obtained with the formalism of the first part of the thesis ; secondly we have studied the aging regime and we have derived that the condition that determines the fluctuation-dissipation ratio is a marginal stability one. In the third part of the thesis we have studied the theory of amorphous states of hard spheres in high dimensions. Hard spheres provide simple models of glasses and they are extensively studied for the jamming transition. In our framework jammed states can be thought as infinite pressure limit of metastable glassy states. During the last years it has been derived a mean field theory of hard spheres based on the 1RSB assumption on the structure of the free energy landscape. However it has been realized that this construction is inconsistent for what concerns the property of the packings at jamming. In the present work we have firstly investigated the possibility of an instability of the 1RSB solution and we have actually found that the 1RSB solution is unstable in the jamming part of the phase diagram. At the same time we have been able to compute the mode-coupling exponent parameter for this system. In order to go beyond the 1RSB solution we have first tried a 2RSB ansatz and then a fullRSB solution. We have derived a set of variational equations that are very close to the ones that have been derived in the Sherrington-Kirkpatrick model. We have solved numerically the equations and we have shown that the fullRSB solution seems to predict that the plateau value of the mean square displacement scale as the pressure to a power close to 3/2 as it seems to be predicted by scaling arguments and in contrast with the 1RSB predictions that show a scaling with the inverse of the pressure. The last chapter of the thesis is on the mode-coupling theory when the glass transition is becoming continuous. We have been able to show that in such a situation a detailed characterization of the solution of the equations can be obtained in the long time regime
Pukhraj, Jain Vardhman Jain. "Cache-Related Delay Server for Aperiodic Job Handling in Real-Time Systems". OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/379.
Texto completo da fonteLarson, Derek A. "Monte Carlo studies of disordered spin systems /". Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
Texto completo da fonteTreiber, Maximilian. "Dephasing in disordered systems at low temperatures". Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-157822.
Texto completo da fontePerondi, Leonel Fernando. "Theoretical studies of diffusion in disordered systems". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334896.
Texto completo da fonteHesselbo, Bobby. "Statistical properties of glassy and disordered systems". Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260771.
Texto completo da fonteBlackburn, Roger Michael. "The statistical mechanics of dilute, disordered systems". Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291289.
Texto completo da fonteWojtas, David Heinrich. "Structure and Diffraction Properties of Disordered Systems". Thesis, University of Canterbury. Electrical and Computer Engineering, 2011. http://hdl.handle.net/10092/5569.
Texto completo da fonteGuy, Carlo Alessandro. "Neutron scattering investigations of some disordered systems". Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240699.
Texto completo da fonteSiak, Selina Chin Yoke. "Localisation and interactions in disordered electron systems". Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292495.
Texto completo da fontePUERTAS, LUIS ALBERTO PECHE. "PHYSICS OF STRONGLY CORRELATED AND DISORDERED SYSTEMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6580@1.
Texto completo da fonteNesta tese estudamos as propriedades físicas de materiais fortemente correlacionados e desordenados, usando Hamiltonianos modelos para descrevê-los. A tese está dividida em duas partes. Na primeira, estudamos o modelo de Anderson periódico para descrever as propriedades de um isolante Kondo. Em particular tomamos o composto de Ce3Bi4Pt3 como paradigma deste tipo de materiais caracterizados por apresentar um pequeno gap(da ordem dos meV ). Na presença de pequenas concentrações de impurezas metálicas como íons de La substituindo os de Ce, como é o caso da liga (Ce1-xLax)Bi4Pt3, sofre uma transição metal-isolante. O Hamiltoniano de Anderson periódico é resolvido a partir da solução de um único sítio atômico que logo é embebido numa rede de Bethe. Este modelo consegue explicar qualitativamente os resultados experimentais como a resistividade em função da temperatura para diferentes concentrações de íons de La, assim como as propriedades óticas do sistema puro. A influência da localização de Anderson nesta transição é analisada a partir do estudo da condutividade elétrica do sistema. A segunda parte está dedicada ao estudo das propriedades de sistemas descritos pelo Hamiltoniano de Falicov- Kimball, largamente utilizado para estudar fenômenos como a transição de valência e metal- isolante, também em compostos de Metais de Transição e Terras Raras. Neste modelo, o caráter destas transições ainda não está bem estabelecido já que o resultado é muito dependente da aproximação utilizada. Utilizamos o Hamiltoniano de Falicov-Kimball sem spin onde a banda de condução é tratada de forma exata já que mostramos a sua equivalência com o problema de uma liga. Os estados f são resolvidos em forma aproximada a partir da equação de movimento, aproximação que chamamos de Aproximação do Estreitamento Dinâmico(AED). Estudamos as propriedades eletrônicas como a ocupação dos estados localizados em função da energia local. Também neste caso, analisamos um sistema desordenado estudando o contraponto entre a correlação eletrônica e a desordem. As diferentes fases que aparecem no sistema como, metálica, isolante de Anderson e de Mott são investigadas em função dos parâmetros que definem o sistema.
In this thesis we study the properties of strongly correlated and disordered materials, using model Hamiltonians to describe them. The thesis is divided in two parts. The first one studies the periodic Anderson model used to describe the properties of a Kondo insulator. In particular we take Ce3Bi4Pt3 as a paradigmatic compound, characterized by a small gap(of the order of meV ). For small concentration of metallic impurities, ions of La substituting Ce, the alloy (Ce1-xLax)Bi4Pt3 suffers a metal- insulator transition. The periodic Anderson Hamiltonian is solved using the atomic solution that is embedded into a Bethe lattice. This model explains the experimental results as the resistivity as a function of temperature for different concentrations of ions of La, as well as, the optical properties of the pure system. The Anderson localization is analyzed studying the electric conductivity of the system. The second part of the thesis is dedicated to study the property of a system described by the Falicov- Kimball Hamiltonian. This Hamiltonian has been used to study the valence and metal-insulator transitions in Transitions Metal and Rare Earth compounds. In this model, the character of these transitions is still not well understood, since it is very dependent of the approximation used. We study the Falicov-Kimball Hamiltonian without spin. The conduction band is exactly described since we show its equivalence with the problem of an alloy. The f states are studied using the equation of motion for the Green functions, decoupling them in a way defined as the Dynamic Narrowing Approximation(DNA). We study the occupation of the local states as a function of energy and other electronic properties. For an alloy the interplay between the electronic correlation and disorder is analized. The different phases that appear in the system, as metallic and Anderson and Mott insulating, are investigated as a function of the parameters that define the system.
Paga, Pierre Andre. "Applications of large deviations in disordered systems". Thesis, King's College London (University of London), 2017. https://kclpure.kcl.ac.uk/portal/en/theses/applications-of-large-deviations-in-disordered-systems(17394a18-1abc-4cd6-90b7-d3fd5a3a9cf5).html.
Texto completo da fonteHiggins, Stewart A. "Neutron scattering studies of disordered magnetic systems". Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/14065.
Texto completo da fonteDobramysl, Ulrich. "On the Relaxation Dynamics of Disordered Systems". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23757.
Texto completo da fontePh. D.
Lindner, John Florian Simon Barry. "Spectral gaps from ordered to disordered systems /". Diss., Pasadena, Calif. : California Institute of Technology, 1989. http://resolver.caltech.edu/CaltechETD:etd-08172005-161212.
Texto completo da fonteMukhopadhyay, Ranjan Goodstein David L. "Quantum phase transitions in disordered Bose systems /". Diss., Pasadena, Calif. : California Institute of Technology, 1998. http://resolver.caltech.edu/CaltechETD:etd-02022007-104407.
Texto completo da fonteArnold, Wolfram Till. "Theory of electron localization in disordered systems /". view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9986736.
Texto completo da fonteTypescript. Includes vita and abstract. Includes bibliographical references (leaves 199-204). Also available for download via the World Wide Web; free to UO users.
Schwab, David Jason. "Topics in biophysics and disordered quantum systems". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1971489301&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Texto completo da fonteKearney, Michael John. "Electron transport in low dimensional disordered systems". Thesis, University of Warwick, 1988. http://wrap.warwick.ac.uk/91877/.
Texto completo da fonteBattistoni, Andrea. "Broad band acoustic spectroscopy in disordered systems". Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/10942.
Texto completo da fonteThe present work of thesis is situated within the framework of the study of disordered systems as liquids and glasses. A liquid is a system characterized by long range translational invariance and by a short range ordered structure. In the liquid state, contrarily to the crystalline one, there is not structural periodicity and all we learnt from solid state physics (Block’s theorem, phonons, Brillouin’s zones, eigen-states of plane waves, etc.) must be fully revised. The macroscopic collective properties of condensed matter are the result of inter and intra-molecular interactions that are typified by characteristic time and space scales. A longstanding and powerful tool to investigate the collective nature of the microscopic processes inside the system is the acoustic spectroscopy. While in the case of crystalline phase we could take advantage of the periodical structure of the system, limiting our investigation to the so called first Brillouin zone, in order to characterize a disordered system we need to explore a widest as possible spectral range to access the all time and space scales in which the dynamical phenomena occur. This approach can be called Broad Band Acoustic Spectroscopy . My PhD activity was devoted to the development of new experimental methods and techniques allowing the exploration with continuity of dynamics evolving with timescales from tenth’s of ns’s to ps’s. I could test such Broad Band Acoustic Spectroscopy on a prototypical sample: acetonitrile, the liquid with highest dipole moment, known for its many different inter- and intra-molecular dynamics. Using several experimental and computational approaches I could characterize the main dynamical processes for such compound in its whole liquid phase. Thanks to the crossing of the all acquired information, it was possible to identify a mutual influence between different relaxations whose behaviour otherwise was not possible to correctly understand. After a brief introduction to contextualize the Broad Band Acoustic Spectroscopy in disordered systems, in Chapter 1 is presented an overview of the experimental techniques used to perform the measurements within this work. In this chapter, the first my original contribution to the extension of acoustic spectral range finds the place. Thanks to the design and realization of particular spatial filters it is now possible to perform Brillouin Light Scattering experiments with angle tunabil- ity without incurring in annoying spurious contributions issues. In the chapter are also recalled the main physical principles at the ground of every presented tech- nique, in particular stressing the complementarity of the energy and time resolved spectroscopies. Because all the information from the inner dynamics of the sample are mediated by the acoustic modes interaction, Chapter 2 is dedicated to the formalism of the density fluctuations, highlighting the differences between the hydrodynamic model, valid at macroscopic length-scales, and the memory functions approach, necessary to describe the mesoscopic region where the characteristic length-scales of the acoustic modes are comparable to the inter-particles distances. In Chapter 3 are shown the experimental results obtained thanks to the Broad Band Spectroscopy in the whole temperature range of the liquid phase of acetoni- trile. We could first measure some thermodynamical quantities by a non linear spectroscopy named Transient Grating, shedding light on the literature debate on them. Among the obtained results, we appreciated a temperature dependency of the heat capacity ratio which is usually considered a constant. Starting from these results and using the filtering approach introduced in Chapter 1, we could profitably study the vibrational relaxation of acetonitrile discovering some relevant discrepan- cies with previous studies. In this way we demonstrated the importance to avoid eventual spurious contributions and to have complementary information from dif- ferent spectral domains. Then there will be shown the results for the so called structural relaxation, obtained in the high energy domain by Inelastic X-ray Scat- tering. A really interesting correlation has been found with the result obtained by the ultrafast response of the Transient Grating method. Once again, to obtain such comparison was necessary to combine the information arising from many different spectral ranges, fact that highlights the utility and endorses the multi-techniques broad band acoustic spectroscopy method. The temperature dependence of the aforementioned relaxation processes sug- gested to evaluate if any coupling there exist between the two. This is exactly what we were able to appreciate in the deep-UV domain and we proposed a phenomeno- logical model to give a picture of the occurring interaction. To further investigate such dynamics coupling effect, could be extremely useful to explore the soft-UV spectral range but so far any technique was able to access such energy domain. In Chapter 4 we thus present our innovative solution to the problem: a novel table top Fabry-Perot interferometer conceived to operate with UV laser source and with only reflecting optics. The last chapters of the thesis describe my contribution to the forthcoming Free Electron Laser (FEL) based experiment to further increase the accessible spectral range to the acoustic spectroscopy: the TIMER project. In particular I will show the result obtained with the pilot experiment named “mini-TIMER” in which we could demonstrate the feasibility of a Transient Grating experiment in the Extreme Ultra Violet (EUV) domain. When TIMER will be operative it will be the first experimental setup able to probe the EUV mesoscopic region of crucial importance for the study of glasses and nano-structures. This result paves the way to a new class of intriguing experiments only matter of theoretical considerations so far: the so called four wave mixing experiments with elemental selectivity.
Il presente lavoro di tesi si colloca nell’ambito dello studio dei sistemi disordi- nati quali liquidi e vetri. Un liquido ´e un sistema caratterizzato da invarianza traslazionale a lungo raggio e da una struttura ordinata a corto raggio. Lo stato liquido, a differenza di quello cristallino, non gode di una periodicit`a strutturale e tutto ci`o che avevamo imparato dalla fisica dello stato solido (teorema di Block, fononi, zone di Brillouin, autostati di onde piane, etc.) deve essere completamente rivisto. Le propriet`a collettive della materia sono il risultato di interazioni a livello inter- e intra-molecolare identificate da caratteristiche scale temporali e spaziali. Uno strumento ormai affermato e utile per lo studio della natura collettiva dei processi microscopici attivi all’interno del sistema ´e la spettroscopia acustica. Mentre nel caso della fase cristallina si poteva sfruttare la natura periodica della struttura del sistema, limitando lo studio alla cosiddetta prima zona di Brillouin, per caratteriz- zare un sistema disordinato ´e necessario esplorare un intervallo spettrale il pi`u ampio possibile cosí da poter aver accesso alle scale spazio-temporali in cui le dinamiche avvengo. Questo tipo di approccio pu`o essere chiamato Spettroscopia Acustica ad Ampia Banda Spettrale . Il mio dottorato ´e stato dedicato allo sviluppo di nuovi metodi e tecniche speri- mentali per esplorare con continuit`a i processi dinamici la cui evoluzione avviene su scale di tempi tra le decine di ns e i ps. Tale Spettroscopia Acustica ad Ampia Banda Spettrale ´e stata testata su un campione prototipo di acetonitrile, il liquido con il pi´u alto momento di dipolo esistente, noto per le sue molteplici dinamiche di orgine inter- e intra-molecolare. Usando diversi approcci sperimentali e computazionali ´e stato possibile caratterizzare i principali processi di rilassamento per tale composto in tutta la sua fase liquida. Combinando poi tutte le informazioni acquisite, ´e stato possibile indentificare una mutua influenza tra i diversi processi di rilassamento il cui comportamento altrimenti sarebbe rimasto incompreso. Dopo una breve introduzione per contestualizzare la Spettroscopia Acustica ad Ampia Banda Spettrale nell’ambito dei sistemi disordinati, nel Capitolo 1 viene offerta una panoramica delle tecniche sperimentali usate per effettuare le misure nel corso di questo lavoro. Trova posto in questo capitolo la descrizione del mio primo originale contributo all’estensione dell’intervallo spettrale acustico. Grazie alla progettazione e realizzazione di particolari filtri spaziali ´e ora possibile effet- tuare esperimenti di diffusione di luce Brillouin con angolo di scattering variabile senza dover incorrere in fastidiosi problemi di contributi spuri. Nel capitolo vengono anche richiamati i principali elementi di fisica alla base di ogni tecnica, marcando in particolare la caratteristica di complementariet`a tra esperimenti risolti in tempo e in energia. Siccome tutte le informazioni a proposito delle dinamiche interne del campione sono mediate dall’interazione coi modi acustici, il Capitolo 2´e dedicato al formalismo delle fluttuazioni di densit`a, evidenziando le differenze tra il modello idrodinamico, valido per scale spaziali macroscopiche, e l’approccio delle funzioni memoria, nec- essario per descrivere la regione mesoscopica dove le dimensioni caratteristiche dei modi acustici diventano confrontabili con le distanze tra le particelle. Nel Capitolo 3 sono riportati i risultati sperimentali ottenuti mediante la Spet- troscopia Acustica ad Ampio Intervallo Spettrale nell’intero range di temperature in cui l’acetonitrile permane allo stato liquido. Per prima cosa, attraverso un tecnica fotonica di spettroscopia non lineare (Transient Grating) ´e stato possibile misurare alcune variabili termodinamiche, potendo fare chiarezza tra i vari contributi presenti in letteratura. Tra i risultati ottenuti, la dipendenza in temperatura del rapporto tra i calori specifici laddove usualmente viene considerata costante. Partendo da questi risultati e usando l’approccio di filtraggio introdotto nel Capitolo 1, ´e stato possibile studiare il rilassamento vibrazionale dell’acetonitrile scoprendo alcune ril- evanti discrepanze con i precedenti lavori riportati in letteratura. Abbiamo cosí dimostrato l’importanza di eliminare eventuali contributi spuri e di poter attingere a informazioni complementari da diversi domini spettrali. Verr`a inoltre mostrato il risultato dello studio del cosiddetto rilassamento strutturale effettuato nel range di alte energie grazie allo Scattering di raggi X. Una interessante correlazione si ´e po- tuta riscontrare tra i risultati di questo esperimento e quelli ottenuti con la tecnica Transient Grating nella sua risposta ultraveloce. Ancora una volta, per ottenere tale risultato ´e stato necessario combinare informazioni provenienti da molti inter- valli spettrali diversi, confermando la validit`a di un approccio multi-tecnica come quello della spettroscopia acustica a larga banda spettrale. L’andamento in tem- peratura dei suddetti processi di rilassamento suggerivano di valutare la presenza di un eventuale accoppiamento tra i due fenomeni. ´E esattamente ci`o che abbiamo osservato esplorando il dominio del profondo ultravioletto e per il quale abbiamo proposto un modello fenomenologico in grado di fornire una rappresentazione delle interazioni in gioco. Per poter approfondire tale fenomeno di accoppiamento sarebbe estremamente utile poter esplorare l’intervallo spettrale degli UV soffici, ma fino ad oggi nessuna tecnica era in grado accedere a tale range. Nel Capitolo 4 mostriamo la nostra innovativa soluzione al problema: un nuovo interferometro Farby-Perot “table-top”, concepito per lavorare con una sorgente UV laser e con sole ottiche riflettive. Gli ultimi capitoli della tesi descrivono il mio contributo al prossimo esperi- mento avente come sorgente di luce un laser ad elettroni liberi: il progetto TIMER, destinato ad aumentare ulteriormente il range spettrale sperimentalmente acces- sibile con la spettroscopia acustica. In particolare, mostrer`o i risultati ottenuti nell’esperimentopilotachiamato“mini-TIMER”graziealqualedimostratolapossibilit`a di effettuare un esperimento Transient Grating anche nel range spettrale dell’estremo UV (EUV). Quando TIMER sar`a operativo sar`a il primo setup sperimentale in grado di sondare la regione mesoscopica nell’EUV, zona di cruciale importanza per lo studio dei vetri e delle nanostrutture. Questo risultato apre inoltre la strada ad una nuova classe di interessanti esperimenti ad oggi oggetto solo di considerazioni teoriche: i cosiddetti esperimenti di “four wave mixing” combinati con la selettivit`a elementale che la radiazione EUV pu`o fornire.
XXVI Ciclo
1985
Chalaev, Oleg. "Nonequilibrium persistent currents in mesoscopic disordered systems". Doctoral thesis, SISSA, 2003. http://hdl.handle.net/20.500.11767/4247.
Texto completo da fonteLennvall, Tomas. "Handling aperiodic tasks and overload in distributed off-line scheduled real-time systems /". Västerås : Mälardalen University, 2003. http://www.mrtc.mdh.se/publications/0541.pdf.
Texto completo da fonteSmyth, M. "Aspects of localisation in off-diagonally disordered systems". Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382663.
Texto completo da fonteSkantzos, Nikolaos Stavrou. "Statistical mechanical analysis of (1 + ∞) dimensional disordered systems". Thesis, King's College London (University of London), 2001. https://kclpure.kcl.ac.uk/portal/en/theses/statistical-mechanical-analysis-of-1--infinity-dimensional-disordered-systems(b16e7dd9-85df-4e71-b8c6-0c6c28062961).html.
Texto completo da fonteLaughton, Stephen Nicholas. "Dynamics of neural networks and disordered spin systems". Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:5531cef6-4682-4750-9c5c-cb69e5e72d64.
Texto completo da fonteGoldbart, P. M. "The statistical mechanics of disordered and frustrated systems". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37707.
Texto completo da fonteThiery, Thimothée. "Analytical methods and field theory for disordered systems". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE017/document.
Texto completo da fonteThis thesis presents several aspects of the physics of disordered elastic systems and of the analytical methods used for their study.On one hand we will be interested in universal properties of avalanche processes in the statics and dynamics (at the depinning transition) of elastic interfaces of arbitrary dimension in disordered media at zero temperature. To study these questions we will use the functional renormalization group. After a review of these aspects we will more particularly present the results obtained during the thesis on (i) the spatial structure of avalanches and (ii) the correlations between avalanches.On the other hand we will be interested in static properties of directed polymers in 1+1 dimension, and in particular in observables related to the KPZ universality class. In this context the study of exactly solvable models has recently led to important progress. After a review of these aspects we will be more particularly interested in exactly solvable models of directed polymer on the square lattice and present the results obtained during the thesis in this direction: (i) classification ofBethe ansatz exactly solvable models of directed polymer at finite temperature on the square lattice; (ii) KPZ universality for the Log-Gamma and Inverse-Beta models; (iii) KPZ universality and non-universality for the Beta model; (iv) stationary measures of the Inverse- Beta model and of related zero temperature models