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Dissertations / Theses on the topic 'Equation de Langevin généralisé'

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Published: 18 May 2024

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1

Malhado, Joaô Pedro Bettencourt Cepêda. "Etudes théoriques de la dynamique impliquant des intersections coniques." Paris 6, 2009. http://www.theses.fr/2009PA066352.

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En chimie moléculaire, l'approximation de Born-Oppenheimer permet d'utiliser le concept de surface d'énergie potentielle à l'échelle atomique. Les intersections coniques (ICs) correspondent aux points où ces surfaces sont dégénérées, et où cette approximation n'est plus valable; les concepts de la dynamique classique y voient leur application réduite et les transitions non-adiabatiques entre ces surfaces deviennent importantes. Les ICs sont particulièrement d'intérêt en photochimie, puisque elles sont responsables de la relaxation électronique non-radiative du premier état excité vers l'état f
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2

Borgman, Jacob. "Fluctuations of the expansion : the Langevin-Raychaudhuri equation /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2004.

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Thesis (Ph.D.)--Tufts University, 2004.<br>Adviser: Larry H. Ford. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 117-120). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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3

Sachs, Matthias Ernst. "The Generalised Langevin Equation : asymptotic properties and numerical analysis." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29566.

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In this thesis we concentrate on instances of the GLE which can be represented in a Markovian form in an extended phase space. We extend previous results on the geometric ergodicity of this class of GLEs using Lyapunov techniques, which allows us to conclude ergodicity for a large class of GLEs relevant to molecular dynamics applications. The main body of this thesis concerns the numerical discretisation of the GLE in the extended phase space representation. We generalise numerical discretisation schemes which have been previously proposed for the underdamped Langevin equation and which are ba
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4

Birrell, Jeremiah, Scott Hottovy, Giovanni Volpe, and Jan Wehr. "Small Mass Limit of a Langevin Equation on a Manifold." SPRINGER BASEL AG, 2016. http://hdl.handle.net/10150/622782.

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12 month embargo; First Online: 11 July 2016<br>We study damped geodesic motion of a particle of mass m on a Riemannian manifold, in the presence of an external force and noise. Lifting the resulting stochastic differential equation to the orthogonal frame bundle, we prove that, as , its solutions converge to solutions of a limiting equation which includes a noise-induced drift term. A very special case of the main result presents Brownian motion on the manifold as a limit of inertial systems.
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5

Schaudinnus, Norbert [Verfasser], and Gerhard [Akademischer Betreuer] Stock. "Stochastic modeling of biomolecular systems using the data-driven Langevin equation." Freiburg : Universität, 2015. http://d-nb.info/1122646887/34.

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6

Siegle, Peter [Verfasser]. "Markovian Embedding of Superdiffusion within a Generalized Langevin Equation Approach / Peter Siegle." München : Verlag Dr. Hut, 2011. http://d-nb.info/1011441683/34.

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7

Caballero-Manrique, Esther. "Langevin Equation approach to bridge different timescales of relaxion in protein dynamics /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1276397961&sid=3&Fmt=2&clientId=11238&RQT=309&VName=PQD.

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Thesis (Ph. D.)--University of Oregon, 2006.<br>Typescript. Includes vita and abstract. Includes bibliographical references (leaves 90-99). Also available for download via the World Wide Web; free to University of Oregon users.
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8

Song, XiaoGeng Ph D. Massachusetts Institute of Technology. "Nonadiabatic electron transfer in the condensed phase, via semiclassical and Langevin equation approach." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/49751.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.<br>Includes bibliographical references (leaves 127-137).<br>In this dissertation, we discuss two methods developed during my PhD study to simulate electron transfer systems. The first method, the semi-classical approximation, is derived from the stationary phase approximation to the path integral in the spin-coherent representation. The resulting equation of motion is a classical-like ordinary differential equation subject to a two-ended boundary condition. The boundary value problem is solved using the "near rea
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9

Pedchenko, B. O., A. S. Yermolenko, Stanislav Ivanovych Denisov, Станіслав Іванович Денисов, and Станислав Иванович Денисов. "Langevin equations for suspended magnetic particles drifting under the Magnus force." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/63757.

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The Magnus effect, i.e., dependence of the trajectory of a body on its rotation, is widely used in sport, science and technical applications. Recently we have shown [1, 2] that due to the Magnus force the single-domain ferromagnetic particles, which are suspended in a viscous fluid and subjected to a harmonic driving force and a non-uniformly rotating magnetic field, can perform drift in a preferred direction. This result has been obtained within the deterministic approach when thermal fluctuations, leading to translational and rotational Brownian motion of particles, are ignored. Our estimati
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10

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)<br>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
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11

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<br>Banca: Raquel Santos Marques de Carvalho<br>Banca: Ricardo D'Elia Matheus<br>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 quant
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12

Bauke, Francisco Conti [UNESP]. "Portadores quentes: modelo browniano." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/91881.

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Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T20:14:03Z : No. of bitstreams: 1 bauke_fc_me_rcla.pdf: 1413465 bytes, checksum: 5695187aaf8a438767e3a8684e26c073 (MD5)<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Neste trabalho estudamos o modelo do movimento Browniano de uma partícula carregada sob a ação de campos elétrico e magnético, externos e homogêneos, no formalismo de Langevin. Calculamos a energia cinética média através do teorema da flutuação-dissipação e obtivemo
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13

Sposini, Vittoria. "A numerical study of fractional diffusion through a Langevin approach in random media." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12494/.

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The study of Brownian motion has a long history and involves many different formulations. All these formulations show two fundamental common results: the mean square displacement of a diffusing particle scales linearly with time and the probability density function is a Guassian distribution. However standard diffusion is not universal. In literature there are numerous experimental measurements showing non linear diffusion in many fields including physics, biology, chemistry, engineering, astrophysics and others. This behavior can have different physical origins and has been found to occur f
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14

Townsend, Peter Stephen Morris. "Diffusion of light adsorbates on transition metal surfaces." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274001.

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Helium-3 surface spin echo spectroscopy (HeSE) has been used to measure the diffusive dynamics of adsorbates on close-packed metal surfaces, namely hydrogen on Cu(111), Pd(111) and Ru(0001), carbon and oxygen on Ru(0001), and oxygen on Cu(111). Chapter 2 reviews the HeSE technique and describes the relevant dynamical models and statistical methods used to interpret data in later chapters. The performance of the ionizing detector is analysed, with a focus on the signal-to-noise ratio. In Chapter 3 expressions for the classical intermediate scattering function (ISF) are introduced for open and c
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15

MARTINS, FERNANDO R. "Medidas de parametros nucleares de um reator de potencia zero aplicando a tecnica de analise de ruidos." reponame:Repositório Institucional do IPEN, 1992. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10294.

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Made available in DSpace on 2014-10-09T12:36:59Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T13:56:23Z (GMT). No. of bitstreams: 1 04494.pdf: 2472493 bytes, checksum: e31b80c363eb669eee7447da1d53b0d6 (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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16

Simand, Catherine. "Etude de la turbulence inhomogène au voisinage d'un tourbillon." Lyon, École normale supérieure (sciences), 2002. http://www.theses.fr/2002ENSL0236.

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Les écoulements fermés entre deux disques coaxiaux corotatifs créés facilement en laboratoire sont turbulents, à hauts Reynolds, et tourbillonnaires à grande échelle, avec une stabilité contrôlée : nous pouvons donc examiner l'interaction entre la vorticité et la turbulence, sur toute la gamme d'échelles de la cascade d'énergie. A grande échelle, des visualisations à l'aide de bulles, de billes et des mesures de vitesse par vélocimétries laser Doppler et à film chaud, permettent la distinction de deux écoulements moyens. Si les disques tournent à la même vitesse, l'écoulement est en rotation g
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17

Zeren, Zafer. "Lagrangian stochastic modeling of turbulent gas-solid flows with two-way coupling in homogeneous isotropic turbulence." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0106/document.

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Dans ce travail de thèse, réalisé à l'IMFT, nous nous sommes intéressés aux écoulements turbulents diphasiques gaz-solides et plus particulièrement au phénomène de couplage inverse qui correspond à la modulation de la turbulence par la phase dispersée. Ce mécanisme est crucial pour les écoulements à forts chargements massiques. Dans cette thèse, nous avons considéré une turbulence homogène isotrope stationnaire sans gravité dans laquelle des particules sont suivies individuellement d'une façon Lagrangienne. La turbulence du fluide porteur est obtenue par des simulations directes (DNS). Les par
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18

Bauke, Francisco Conti. "Portadores quentes : modelo browniano /." Rio Claro : [s.n.], 2011. http://hdl.handle.net/11449/91881.

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Orientador: Roberto E. Lagos Monaco<br>Banca: José Antonio Roversi<br>Banca: Bernardo Laks<br>Resumo: Neste trabalho estudamos o modelo do movimento Browniano de uma partícula carregada sob a ação de campos elétrico e magnético, externos e homogêneos, no formalismo de Langevin. Calculamos a energia cinética média através do teorema da flutuação-dissipação e obtivemos uma expressão para a temperatura efetiva das partículas Brownianas em função da temperatura do reservatório e dos campos externos. Esta temperatura efetiva mostrou-se sempre maior que a temperatura do reservatório, o que explica a
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19

Miserocchi, Andrea. "The Fokker-Planck equation as model for the stochastic gradient descent in deep learning." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18290/.

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La discesa stocastica del gradiente (SGD) è alla base degli algoritmi di ottimizzazione di reti di Deep Learning più usati in AI, dal riconoscimento delle immagini all’elaborazione del linguaggio naturale. Questa tesi si propone di descrivere un modello basato sull’equazione di Fokker-Planck della dinamica del SGD. Si introduce la teoria dei processi stocastici, con particolare enfasi sulle equazioni di Langevin e sull’equazione di Fokker-Planck. Si mostra come il SGD minimizzi un funzionale sulla densità di probabilità dei pesi, non dipendente direttamente dalla funzione di costo. Infine si
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20

Brännlund, Niklas. "Modeling and implementation of dense gas effects in a Lagrangian dispersion model." Thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105203.

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The use of hazardous toxic substances is very common in the industrial sector. The substances are often stored in tanks in storage compartments or transported between industrial premises. In case of an accident involving these substances, severe harm can affect both population and the environment. This leaves a demand for an accurate prediction of the substance concentration distribution to mitigate the risks as much as possible and in advance create suitable safety measures. Toxic gases and vapors are often denser than air making it affected by negative buoyancy forces. This will make the gas
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21

Dangerfield, C. E. "Stochastic models of ion channel dynamics and their role in short-term repolarisation variability in cardiac cells." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:cd0be850-1ff0-4792-8171-438ff8fc0161.

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Sudden cardiac death due to the development of lethal arrhythmias is the dominant cause of mortality in the UK, yet the mechanisms underlying their onset, maintenance and termination are still poorly understood. Therefore biomarkers are used to determine arrhythmic risk within patients and of new drug compounds. In recent years, the magnitude of variations in the length of successive beats, measured over a short period of time, has been shown to be a powerful predictor of arrhythmic risk. This beat-to-beat variability is thought to be the manifestation of the random opening and closing dynamic
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22

Денисов, Станіслав Іванович, Станислав Иванович Денисов, Stanislav Ivanovych Denysov та ін. "Эффективная система уравнений Ланжевена для вращательного движения однодоменных ферромагнитных частиц". Thesis, Сумский государственный университет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39677.

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При описании открытых систем влияние внешней среды часто моделируется гауссовским белым шумом. Если в уравнениях Ланжевена, описывающих такие системы, шум мультипликативный, тогда возникает проблема выбора его интерпретации, поскольку от этого могут зависеть статистические свойства изучаемой системы. С этой проблемой тесно связана и другая – нахождение приведенных уравнений Ланжевена, которые гораздо проще исходных, но имеют эквивалентные (в статистическом смысле) решения. В данной работе отмеченные выше проблемы решены для векторного уравнения Ланжевена.
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23

Wu, Yong. "Relaxation Effects in Magnetic Nanoparticle Physics: MPI and MPS Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1370865200.

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24

Mélykúti, Bence. "Theoretical advances in the modelling and interrogation of biochemical reaction systems : alternative formulations of the chemical Langevin equation and optimal experiment design for model discrimination." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:d368c04c-b611-41b2-8866-cde16b283b0d.

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This thesis is concerned with methodologies for the accurate quantitative modelling of molecular biological systems. The first part is devoted to the chemical Langevin equation (CLE), a stochastic differential equation driven by a multidimensional Wiener process. The CLE is an approximation to the standard discrete Markov jump process model of chemical reaction kinetics. It is valid in the regime where molecular populations are abundant enough to assume their concentrations change continuously, but stochastic fluctuations still play a major role. We observe that the CLE is not a single equatio
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25

Evola, Salvatore. "Modelling of the sedimentation phenomenon of solid particles immersed in a turbulent fluid." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20077/.

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Settling phenomenon of solid particles immersed in a turbulent fluid has been investigated, in a condition of free-stream turbulence. Since structures formed onto this condition are complex, it is difficult to predict exactly how particles move. It is thus appropriate to conduct deepen studies of the phenomenon and carry out simulations to describe particles’ settling velocity. In order to define a new correlation for the evaluation of particles’ settling velocity, different literature correlations and parameters have been exploited. Langevin dynamics has been used to describe fluid’s mo
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Lagache, Thibault. "Modeling the early steps of viral infection : a stochastic approach." Paris 6, 2009. http://www.theses.fr/2009PA066470.

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27

Kopec, Marie. "Quelques contributions à l'analyse numérique d'équations stochastiques." Electronic Thesis or Diss., Rennes, École normale supérieure, 2014. http://www.theses.fr/2014ENSR0002.

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Ce travail présente quelques résultats concernant le comportement en temps fini et en temps long de méthodes numériques pour des équations stochastiques. On s'intéresse d'abord aux équations différentielles stochastiques de Langevin et de Langevin amorti. On montre un résultat concernant l'analyse d'erreur faible rétrograde de ses équations par des schémas numériques implicites. En particulier, on montre que l'erreur entre le générateur associé au schéma numérique et la solution d'une équation de Kolmogorov modifiée est d'ordre élevé par rapport au pas de discrétisation. On montre aussi que la
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Angeletti, Andrea. "Collective dynamics of active particles." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16772/.

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Il nostro scopo è lo studio e il confronto della dinamica di particelle passive e attive in un fluido. Vengono inoltre introdotti i modelli matematici che permettono di simulare il loro comportamento. Sono studiate le propietà e la soluzione numerica dell'equazione di Langevin nella sua approsimazione in regime 'overdamped'. Mostriamo come lo spostamento quadratico medio delle particelle passive sia diffusivo, i.e. lineare nel tempo, e proporzionale al coefficiente di diffusione lineare, mentre quello di particelle attive quadratico per un tempo minore dell'inverso del coefficiente di diffusi
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Ющенко, Ольга Володимирівна, Ольга Владимировна Ющенко, Olha Volodymyrivna Yushchenko та М. А. Руденко. "Дослідження колективних ефектів при обертальному русі наночастинок". Thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/67932.

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Останнім часом увагу вчених все частіше привертають проблеми, пов’язані з описом руху наночастинок. Це пов’язано з новітніми технологічними розробками із застосуванням наночастинок. Завдяки контрольованому руху наночастинок можна створювати нові матеріали із заданими властивостями та архітектурою, збирати мікро- та нано-пристрої, контролювати різні каталітичні реакції, організовувати доставку ліків в конкретні точки живих організмів.
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Garofalo, Marco. "Dynamics of numerical stochastic perturbation theory." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31086.

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Numerical Stochastic Perturbation theory is a powerful tool for estimating high-order perturbative expansions in lattice quantum field theory. The standard algorithm based on the Langevin equation, however, suffers from several limitations which in practice restrict the potential of this technique: first of all it is not exact, a sequence of simulations with finer and finer discretization of the relevant equations have to be performed in order to extrapolate away the systematic errors in the results; and, secondly, the numerical simulations suffer from critical slowing down as the continuum li
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Radtke, Paul Kaspar. "Mesoscopic Models of Stochastic Transport." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19152.

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Transportphänomene treten in biologischen und künstlichen Systemen auf allen Längenskalen auf. In dieser Arbeit untersuchen wir sie für verschiedene Systeme aus einer mesoskopischen Perspektive, in der Fluktuationen physikalischer Größen um ihre Mittelwerte eine wichtige Rolle spielen. Im ersten Teil untersuchen wir die persistente Bewegung aktiver Brownscher Teilchen mit zusätzlichem Drehmoment, wie sie z.B. für Spermien oder Janus Teilchen auftritt. Wird ihre Bewegung auf einen Tunnel variierender Breite beschränkt, so setzt im thermischen Nichtgleichgewicht Transport ein; ungericht
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Jen, Hsiang-Hua. "Theory of light-matter interactions in cascade and diamond type atomic ensembles." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37288.

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In this thesis, we investigate the quantum mechanical interaction of light with matter in the form of a gas of ultracold atoms: the atomic ensemble. We present a theoretical analysis of two problems, which involve the interaction of quantized electromagnetic fields (called signal and idler) with the atomic ensemble (i) cascade two-photon emission in an atomic ladder configuration, and (ii) photon frequency conversion in an atomic diamond configuration. The motivation of these studies comes from potential applications in long-distance quantum communication where it is desirable to generate qu
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Katz, Roland. "A quantum approach to dynamical quarkonia suppression in high energy heavy ion collisions." Thesis, Nantes, Ecole des Mines, 2015. http://www.theses.fr/2015EMNA0227/document.

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La chromodynamique quantique (QCD) prédit l'existence d'un nouvel état de la matière : le plasma de quarks et de gluons (PQG). Celui-ci aurait existé dans les premiers instants suivant le Big Bang et peut en principe être produit sous les conditions extrêmes de température et de densité atteintes lors de collisions d'ions lourds à haute énergie (au LHC par exemple). Un des marqueurs de sa présence est la suppression des quarkonia (états liés de quark/antiquark lourds), caractérisée par une production inférieure de ces états dans les collisions d'ions lourds relativement aux collisions proton-p
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Silva, Leandro Alexandre da. "Processos estocásticos em teoria de campos e aplicação ao universo inflacionário." Universidade do Estado do Rio de Janeiro, 2009. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7006.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>É conhecido que derivações microscópicas obtidas através de métodos de teoria quântica de campos (TQC) podem conduzir a complicadas equações de movimento (EdM) que possuem um termo dissipativo com memória e um termo de ruído colorido. Um caso particularmente interessante é o modelo que escreve a interação entre um sistema e um banho térmico a temperatura T. Motivado por isso, usamos uma prescrição que nos permite reescrever EdMs não-markovianas semelhantes as obtidas em TQC em termos de um sistema de equações locais, para então c
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Alves, Claudia Marins. "Stochastic models for the treatment of dispersion in the atmosphere." Laboratório Nacional de Computação Científica, 2006. http://www.lncc.br/tdmc/tde_busca/arquivo.php?codArquivo=135.

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Lagrangian stochastic models are a largely used tool in the study of passive substances dispersion inside the Atmospheric Boundary Layer. Its application is related to the trajectory computation of thousands of particles, that numerically simulate the dispersion of suspense substances in the atmosphere. In this study, the basic concepts related to the Lagrangian stochastic modelling are presented and discussed together with its main characteristics and its computational implementation, to the study of particles dispersion in the atmosphere. In a computational experiment, the obtained result
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Francisquini, Elton. "Caracterização das propriedades morfológicas, estruturais e magnéticas de nanopartículas Fe3O4 e Fe2CoO4 em matriz orgânica." reponame:Repositório Institucional da UFABC, 2013.

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37

Heidernätsch, Mario. "On the diffusion in inhomogeneous systems." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-169979.

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Ziel dieser Arbeit ist die Untersuchung des Einflusses der stochastischen Interpretation der Langevin Gleichung mit zustandsabhängigen Diffusionskoeffizienten auf den Propagator des zugehörigen stochastischen Prozesses bzw. dessen Mittelwerte. Dies dient dem besseren Verständnis und der Interpretation von Messdaten von Diffusion in inhomogenen Systemen und geht einher mit der Frage der Form der Diffusionsgleichung in solchen Systemen. Zur Vereinfachung der Fragestellung werden in dieser Arbeit nur Systeme untersucht die vollständig durch einen ortsabhängigen Diffusionskoeffizienten und Angabe
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38

Hannay, Jonathan David. "Computational simulations of thermally activated magnetisation dynamics at high frequencies." Thesis, Bangor University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367315.

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39

Cohen, Jack Andrew. "Active colloids and polymer translocation." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:e8fd2e5d-f96f-4f75-8be8-fc506155aa0f.

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This thesis considers two areas of research in non-equilibrium soft matter at the mesoscale. In the first part we introduce active colloids in the context of active matter and focus on the particular case of phoretic colloids. The general theory of phoresis is presented along with an expression for the phoretic velocity of a colloid and its rotational diffusion in two and three dimensions. We introduce a model for thermally active colloids that absorb light and emit heat and propel through thermophoresis. Using this model we develop the equations of motion for their collective dynamics and con
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Вітренко, Андрій Миколайович, Андрей Николаевич Витренко та Andrii Mykolaiovych Vitrenko. "Стабилизация равновесного состояния динамической системы при воздействии взаимно-коррелированных шумов". Thesis, Сумский государственный университет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/67928.

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Рассматривается стохастическая динамическая система, которая описывается уравнением Ланжевена с линейной возвращающей силой и двумя взаимно-коррелированными гауссовскими белыми шумами, один из которых – аддитивный, другой – мультипликативный. Система имеет равновесное состояние в x = 0. При отрицательной взаимной корреляции каждый из шумов характеризуется критической амплитудой, при которой в системе индуцируется унимодальный-бимодальный переход.
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41

Arenas, Zochil González. "Formulação supersimétrica de processos estocásticos com ruído multiplicativo." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=4684.

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Centro Latino-Americano de Física<br>Os processos estocásticos com ruído branco multiplicativo são objeto de atenção constante em uma grande área da pesquisa científica. A variedade de prescrições possíveis para definir matematicamente estes processos oferece um obstáculo ao desenvolvimento de ferramentas gerais para seu tratamento. Na presente tese, estudamos propriedades de equilíbrio de processos markovianos com ruído branco multiplicativo. Para conseguirmos isto, definimos uma transformação de reversão temporal de tais processos levando em conta que a distribuição estacionária de probabili
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Alves, Claudia Marins. "Modelos estocásticos para tratamento da dispersão de material particulado na atmosfera." Laboratório Nacional de Computação Científica, 2006. https://tede.lncc.br/handle/tede/62.

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Made available in DSpace on 2015-03-04T18:50:49Z (GMT). No. of bitstreams: 1 tese.pdf: 5590910 bytes, checksum: a89ccd96ade2b696f0e5b9163dc31bf5 (MD5) Previous issue date: 2006-11-13<br>Lagrangian stochastic models are a largely used tool in the study of passive substances dispersion inside the Atmospheric Boundary Layer. Its application is related to the trajectory computation of thousands of particles, that numerically simulate the dispersion of suspense substances in the atmosphere. In this study, the basic concepts related to the Lagrangian stochastic modelling are presented and discu
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Yilmaz, Bulent. "Stochastic Approach To Fusion Dynamics." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608517/index.pdf.

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This doctoral study consists of two parts. In the first part, the quantum statistical effects on the formation process of the heavy ion fusion reactions have been investigated by using the c-number quantum Langevin equation approach. It has been shown that the quantum effects enhance the over-passing probability at low temperatures. In the second part, we have developed a simulation technique for the quantum noises which can be approximated by two-term exponential colored noise.
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Mostefai, Mohamed Sadek. "Déduction rigoureuse de l'équation de Reynolds à partir d'un système modélisant l'écoulement à faible épaisseur d'un fluide micropolaire, et étude de deux problèmes à frontière libre : Hele-Shaw généralisé et Stephan à deux phases pour un fluide non newtonien." Saint-Etienne, 1997. http://www.theses.fr/1997STET4019.

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Dans le chapitre 1, on considère le modèle micropolaire de Navier-Stokes avec conditions de bords de type Dirichlet non homogènes en dimension deux. On donnera un résultat d'existence d'une solution faible en utilisant le théorème du point fixe de Leray-Schauder, puis on prouvera l'unicité de la solution faible du problème sous certaines hypothèses. On établiera une justification mathématique de l’équation de Reynolds généralisé à partir de ce modèle là. On étudiera ensuite la forme de l'équation de Reynolds suivant le choix de la viscosité et des données initiales. Dans le chapitre 2, nous co
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Santos, Joao Rafael Lucio dos. "Tópicos em defeitos deformados e o movimento Browniano." Universidade Federal da Paraí­ba, 2013. http://tede.biblioteca.ufpb.br:8080/handle/tede/5748.

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Made available in DSpace on 2015-05-14T12:14:12Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3660633 bytes, checksum: 7309d28729d29dd071bc87f7c5609ebc (MD5) Previous issue date: 2013-11-20<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>The non-linear science is a central topic covering several investigation areas, such as biology, chemistry, mathematics and physics. In the first part of this thesis, we studied the non-linearity in the scope of classical field theory. The discussions are based on static solutions in (1, 1) space-time dimensions, and they are
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Le, Thanh Binh. "Sur le problème de coefficient et la multifractalité de whole-plane SLE." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2028/document.

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Le point de départ de cette thèse est la conjecture de Bieberbach : sa démonstration par De Branges utilise deux ingrédients, à savoir la théorie de Loewner des domaines plans croissants et une inégalité de Milin qui concerne les coefficients logarithmiques. Nous commençons par étudier les coefficients logarithmiques du whole-plane SLE en utilisant une méthode combinatoire, assistée par ordinateur. Nous retrouvons les résultats en utilisant une équation aux dérivées partielles analogue à celle obtenue par Beliaev et Smirnov. Nous généralisons ces résultats en définissant le spectre généralisé
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Ceccato, Alessandro. "Approaches to dimensionality reduction and model simplification of dynamics in the chemical context." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426709.

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Much of the effort in the modern chemical and physical sciences is devoted to the study of complex dynamical phenomena. Such a study is often hampered by the considerable complexity (i.e., the high dimensionality) exhibited by the systems of interest. In this research project, of theoretical and methodological character, we explore some facets of the topics of model reduction and simplification of complex dynamics, both deterministic and stochastic. In particular, in the first part of the work (chs. 2-5), we focus on deterministic systems. In chapter 2, starting from the findings of two
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48

Weiß, Richard Gregor. "The role of water in the kinetics of hydrophobic molecular recognition investigated by stochastic modeling and molecular simulations." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18814.

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Die Assoziation kleiner Moleküle (Liganden) in hydrophobe Bindungstaschen spielt eine fundamentale Rolle in der Biomolekularerkennung und den Selbstassemblierungsprozessen der physikalischen Chemie wässriger Lösungen. Während der Einfluss des Wassers auf die freie Energie der Bindung (die Bindungsaffinität) im thermischen Gleichgewicht in den letzten Jahren auf immer stärkere Aufmerksamkeit stößt, ist die Rolle des Wassers in der Kinetik und der Bestimmung der Bindungsraten noch weitestgehend unverstanden. Welche nanoskaligen Effekte des Wassers beeinflussen die Dynamik des Liganden in der Näh
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49

Pereira, Mike. "Champs aléatoires généralisés définis sur des variétés riemanniennes : théorie et pratique." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM055.

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La géostatistique est la branche des statistiques s’intéressant à la modélisation des phénomènes ancrés dans l’espace au travers de modèles probabilistes. En particulier, le phénomène en question est décrit par un champ aléatoire (généralement gaussien) et les données observées sont considérées comme résultant d’une réalisation particulière de ce champ aléatoire. Afin de faciliter la modélisation et les traitements géostatistiques qui en découlent, il est d’usage de supposer ce champ comme stationnaire et donc de supposer que la structuration spatiale des données se répète dans le domaine d’ét
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50

Schlichting, André. "The Eyring-Kramers formula for Poincaré and logarithmic Sobolev inequalities." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-97965.

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The topic of this thesis is a diffusion process on a potential landscape which is given by a smooth Hamiltonian function in the regime of small noise. The work provides a new proof of the Eyring-Kramers formula for the Poincaré inequality of the associated generator of the diffusion. The Poincaré inequality characterizes the spectral gap of the generator and establishes the exponential rate of convergence towards equilibrium in the L²-distance. This result was first obtained by Bovier et. al. in 2004 relying on potential theory. The presented approach in the thesis generalizes to obtain also a
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