Дисертації з теми "Random walk processses"
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Jones, Elinor Mair. "Large deviations of random walks and levy processes." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491853.
Повний текст джерелаBuckley, Stephen Philip. "Problems in random walks in random environments." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:06a12be2-b831-4c2a-87b1-f0abccfb9b8b.
Повний текст джерелаOosthuizen, Joubert. "Random walks on graphs." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86244.
Повний текст джерелаENGLISH ABSTRACT: We study random walks on nite graphs. The reader is introduced to general Markov chains before we move on more specifically to random walks on graphs. A random walk on a graph is just a Markov chain that is time-reversible. The main parameters we study are the hitting time, commute time and cover time. We nd novel formulas for the cover time of the subdivided star graph and broom graph before looking at the trees with extremal cover times. Lastly we look at a connection between random walks on graphs and electrical networks, where the hitting time between two vertices of a graph is expressed in terms of a weighted sum of e ective resistances. This expression in turn proves useful when we study the cover cost, a parameter related to the cover time.
AFRIKAANSE OPSOMMING: Ons bestudeer toevallige wandelings op eindige gra eke in hierdie tesis. Eers word algemene Markov kettings beskou voordat ons meer spesi ek aanbeweeg na toevallige wandelings op gra eke. 'n Toevallige wandeling is net 'n Markov ketting wat tyd herleibaar is. Die hoof paramaters wat ons bestudeer is die treftyd, pendeltyd en dektyd. Ons vind oorspronklike formules vir die dektyd van die verdeelde stergra ek sowel as die besemgra ek en kyk daarna na die twee bome met uiterste dektye. Laastens kyk ons na 'n verband tussen toevallige wandelings op gra eke en elektriese netwerke, waar die treftyd tussen twee punte op 'n gra ek uitgedruk word in terme van 'n geweegde som van e ektiewe weerstande. Hierdie uitdrukking is op sy beurt weer nuttig wanneer ons die dekkoste bestudeer, waar die dekkoste 'n paramater is wat verwant is aan die dektyd.
Jones, Owen Dafydd. "Random walks on pre-fractals and branching processes." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388440.
Повний текст джерелаBoutaud, Pierre. "Branching random walk : limit cases and minimal hypothesis." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASM025.
Повний текст джерелаThe branching random walk is a particle system on the real line starting at time 0 with an initial particle at position 0, then each particle living at time n proceeds to die at time n+1 and give birth, independently from the other particles of generation n, to a random number of particles at random positions. In a first chapter, we define in details the branching random walk model and some key elements of the scientific research on this model, including the study of the additive martingale. This martingale can be stuided through its convergence towards a limit that may be trivial, raising the question of an appropriate scaling, called Seneta-Heyde sclaing, in the case the limit is trivial. The additive martingale can also be studied with stochastic recursive equations lezading to fixed points equations in law. This latter question is adressed in some unpublished works from the first year of PhD, in continuioty with works from the masters thesis. The second chapter is a translation in english of some sections of the preivous chapter so that every reader can grasp the key elements and goals of this manuscript.In a third chapter, we present a new proof developed with Pascal Maillard for Aîdékon and Shi's theorem on the Seneta-Heyde scaling of the critical additive martingale in the finite variance case. This new proof no longer need a peeling lemma and the use of second moment arguments and prefers studying the conditional Laplace transform. the properties of some renewal functions allow a much more general approach without the need to foucs to much on the derivative martingale. This is also illustrated in a fourth chapter where in new works with Pascal Maillard, we find the Seneta-Heyde scaling for the critical additive martingale in the case where the spinal random walk is in the attraction domain of a stable law. We then observe that the renewal functions provide us with a better suited candidate for this study than the derivative artingale, which is no longer always a martingale in this context.Finally, the fifth chapter focus on the question of the optimality of the assumptions made in the preivous chapter concerning the non-triviality of the limit obtained with the Seneta-Heyde scaling
Tokushige, Yuki. "Random Walks on random trees and hyperbolic groups: trace processes on boundaries at infinity and the speed of biased random walks." Kyoto University, 2019. http://hdl.handle.net/2433/242580.
Повний текст джерелаDe, Bacco Caterina. "Decentralized network control, optimization and random walks on networks." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112164/document.
Повний текст джерелаIn the last years several problems been studied at the interface between statistical physics and computer science. The reason being that often these problems can be reinterpreted in the language of physics of disordered systems, where a big number of variables interacts through local fields dependent on the state of the surrounding neighborhood. Among the numerous applications of combinatorial optimisation the optimal routing on communication networks is the subject of the first part of the thesis. We will exploit the cavity method to formulate efficient algorithms of type message-passing and thus solve several variants of the problem through its numerical implementation. At a second stage, we will describe a model to approximate the dynamic version of the cavity method, which allows to decrease the complexity of the problem from exponential to polynomial in time. This will be obtained by using the Matrix Product State formalism of quantum mechanics. Another topic that has attracted much interest in statistical physics of dynamic processes is the random walk on networks. The theory has been developed since many years in the case the underneath topology is a d-dimensional lattice. On the contrary the case of random networks has been tackled only in the past decade, leaving many questions still open for answers. Unravelling several aspects of this topic will be the subject of the second part of the thesis. In particular we will study the average number of distinct sites visited during a random walk and characterize its behaviour as a function of the graph topology. Finally, we will address the rare events statistics associated to random walks on networks by using the large-deviations formalism. Two types of dynamic phase transitions will arise from numerical simulations, unveiling important aspects of these problems. We will conclude outlining the main results of an independent work developed in the context of out-of-equilibrium physics. A solvable system made of two Brownian particles surrounded by a thermal bath will be studied providing details about a bath-mediated interaction arising for the presence of the bath
Maddalena, Daniela. "Stationary states in random walks on networks." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10170/.
Повний текст джерелаGabrysch, Katja. "On Directed Random Graphs and Greedy Walks on Point Processes." Doctoral thesis, Uppsala universitet, Analys och sannolikhetsteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305859.
Повний текст джерелаBernergård, Zandra. "Connection between discrete time random walks and stochastic processes by Donsker's Theorem." Thesis, Mälardalens högskola, Akademin för utbildning, kultur och kommunikation, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-48719.
Повний текст джерелаRocha, Josué Macario de Figueirêdo. "Passeio aleatório unidimensional com ramificação em um meio aleatório K-periódico." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-19042014-222336/.
Повний текст джерелаWe study a \"supercritical\" branching random walk on Z+ in a one-dimensional non i.i.d. random environment, which considers both the branching mechanism and the step transition. Criteria of (strong) recurrence and transience are presented for this model.
Eberz-Wagner, Dorothea M. "Discrete growth models /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/5797.
Повний текст джерелаAbdel-Rehim, Entsar Ahmed Addalla. "Modelling and simulating of classical and non-classical diffusion processes by random walks." [S.l.] : [s.n.], 2004. http://www.diss.fu-berlin.de/2004/168/index.html.
Повний текст джерелаAbdel-Rehim, Entsar A. "Modelling and simulating of classical and non-classical diffusion processes by random walks." [S.l. : s.n.], 2004. http://www.diss.fu-berlin.de/2004/168/index.html.
Повний текст джерелаLacroix-A-Chez-Toine, Bertrand. "Extreme value statistics of strongly correlated systems : fermions, random matrices and random walks." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS122/document.
Повний текст джерелаPredicting the occurrence of extreme events is a crucial issue in many contexts, ranging from meteorology to finance. For independent and identically distributed (i.i.d.) random variables, three universality classes were identified (Gumbel, Fréchet and Weibull) for the distribution of the maximum. While modelling disordered systems by i.i.d. random variables has been successful with Derrida's random energy model, this hypothesis fail for many physical systems which display strong correlations. In this thesis, we study three physically relevant models of strongly correlated random variables: trapped fermions, random matrices and random walks.In the first part, we show several exact mappings between the ground state of a trapped Fermi gas and ensembles of random matrix theory. The Fermi gas is inhomogeneous in the trapping potential and in particular there is a finite edge beyond which its density vanishes. Going beyond standard semi-classical techniques (such as local density approximation), we develop a precise description of the spatial statistics close to the edge. This description holds for a large universality class of hard edge potentials. We apply these results to compute the statistics of the position of the fermion the farthest away from the centre of the trap, the number of fermions in a given domain (full counting statistics) and the related bipartite entanglement entropy. Our analysis also provides solutions to open problems of extreme value statistics in random matrix theory. We obtain for instance a complete description of the fluctuations of the largest eigenvalue in the complex Ginibre ensemble.In the second part of the thesis, we study extreme value questions for random walks. We consider the gap statistics, which requires to take explicitly into account the discreteness of the process. This question cannot be solved using the convergence of the process to its continuous counterpart, the Brownian motion. We obtain explicit analytical results for the gap statistics of the walk with a Laplace distribution of jumps and provide numerical evidence suggesting the universality of these results
Vásquez, Mercedes Claudia Edith 1989. "Limite superior sobre a probabilidade de confinamento de passeio aleatório em meio aleatório." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306837.
Повний текст джерелаDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica
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Mestrado
Estatistica
Mestra em Estatística
Schmid, Patrick. "Random processes in truncated and ordinary Weyl chambers." Doctoral thesis, Universitätsbibliothek Leipzig, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-66394.
Повний текст джерелаBorrello, Davide. "Interacting particle systems : stochastic order, attractiveness and random walk on small world grahs." Rouen, 2009. http://www.theses.fr/2009ROUES032.
Повний текст джерелаThe main subject of the thesis is concerned with interacting particle systems, which are classes of spatio-temporal stochastic processes describing the evolution of particles in interaction with each other on a finite or infinite discrete space. In part I we investigate the stochastic order in a particle system with multiple births, deaths and jumps on the d-dimensional lattice. We give applications on biological models of spread of epidemics and metapopulations dynamics systems. In part II we analyse the coalescing random walk in a class of finite random graphs modeling social networks, the small world graphs
Lima, Marcelo Felisberto de. "Processos estocásticos não-markovianos em difusão anômala." Universidade Federal de Alagoas, 2010. http://repositorio.ufal.br/handle/riufal/1017.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
Um clássico problema em física consiste em difusão normal versus anômala. Análise fractal de caminhadas aleatórias com memória, sugere descrever quantitativamente uma fenomenologia complexa observada em economia, ecologia, biologia, e física. Processos Markovianos estão representados em caminhadas aleatórias com memória de curto alcance. Em contraste, memória de longo alcance surge tipicamente em caminhadas não-Markovianas. O caso mais extremo de uma caminhada não-Markoviana corresponde a um processo estocástico com dependência em sua história completa. Estudamos uma proposta recente de caminhada não-Markoviana caracterizada por perda de memória do passado recente e persistência induzida amnesicamente. Apresento resultados analíticos mostrando um diagrama de fase completo, consistindo de 4 fases. (i) não-persistente clássico, (ii) persistente clássico controlado por feedback positivo, (iii) não-persistente log-periódico e (iv) persistente log-periódico controlado por feedback negativo. As primeiras duas fases apresentam invariância de escala em simetria contínua. Em compensação, movimento log-periódico apresenta invariância de escala em simetria discreta, com dimensão complexa maior do que a dimensão fractal real. É mostrado evidências de persistência log-periódica não somente estatísticas, mas devido também a auto-similaridade geométrica. Obtivemos os resultados numéricos e analíticos para seis expoentes críticos, que juntos caracterizam completamente as propriedades das transições.
Chupeau, Marie. "Différentes propriétés de marches aléatoires avec contraintes géométriques et dynamiques." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066167/document.
Повний текст джерелаWe first determine the impact of an infinite reflecting wall on the space occupied by a planar Brownian motion at a fixed observation time. We characterize it by the mean perimeter of its convex hull, defined as the minimal convex polygon enclosing the whole trajectory. We also determine the mean length of the visited portion of the wall, and the survival probability of a Brownian walker in an absorbing wedge.We then study the time needed for a lattice random walker to visit every site of a confined volume, or a fraction of them. We calculate the mean value of this so-called cover time in one dimension for a persistant random walk. We also determine the distribution of the cover time and related observables for the class of non compact processes, which describes a wide range of random searches.After that, we calculate and analyze the splitting probability of a one-dimensional Brownian walker evolving in an expanding or contracting interval.Last, we study several aspects of the model of starving random walk, where the walker starves if its visits to new sites, from which it collects resources, are not regular enough. We develop a mean-field treatment of this model in two dimensions, then determine the impact of regeneration of resources on the survival properties of the walker. We finally consider a model of exploitation of food patches taking explicitly into account the displacement of the walker in the patches, which can be mapped onto the starving random walk model
Strandlund, Henrik. "Simulation of diffusional processes in alloys : techniques and applications." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-399.
Повний текст джерелаMallein, Bastien. "Marches aléatoires branchantes, temps inhomogène, sélection." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066104/document.
Повний текст джерелаIn this thesis, we take interest in the branching random walk, a particles system, in which particles move and reproduce independently. The aim is to study the rhythm at which these particles invade their environment, a quantity which often reveals information on the past of the extremal individuals. We take care of two particular variants of branching random walk, that we describe below.In the first variant, the way individuals behave evolves with time. This model has been introduced by Fang and Zeitouni in 2010. This time-dependence can be a slow evolution of the reproduction mechanism of individuals, at macroscopic scale, in which case the maximal displacement is obtained through the resolution of a convex optimization problem. A second kind of time-dependence is to sample at random, at each generation, the way individuals behave. This model has been introduced and studied in an article in collaboration with Piotr Mi\l{}os.In the second variant, individuals endure a Darwinian selection mechanism. The position of an individual is understood as its fitness, and the displacement of a child with respect to its parent is associated to the process of heredity. In such a process, the total size of the population is fixed to some integer N, and at each step, only the N fittest individuals survive. This model was introduced by Brunet, Derrida, Mueller and Munier. In a first time, we took interest in a mechanism of reproduction which authorises some large jumps. In the second model we considered, the total size N of the population may depend on time
Nava-Sedeño, Josue Manik, Haralampos Hatzikirou, Rainer Klages, and Andreas Deutsch. "Cellular automaton models for time-correlated random walks: derivation and analysis." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-231568.
Повний текст джерелаTejedor, Vincent. "Random walks and first-passage properties : trajectory analysis and search optimization." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00721294.
Повний текст джерелаWang, Hanyang. "Two Examples of Ratchet Processes in Microfluidics." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37649.
Повний текст джерелаNava-Sedeño, Josue Manik, Haralampos Hatzikirou, Rainer Klages, and Andreas Deutsch. "Cellular automaton models for time-correlated random walks: derivation and analysis." Nature Publishing Group, 2017. https://tud.qucosa.de/id/qucosa%3A30690.
Повний текст джерелаMallmann-Trenn, Frederik. "Analyse probabiliste de processus distribués axés sur les processus de consensus." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE058/document.
Повний текст джерелаThis thesis is devoted to the study of stochastic decentralized processes. Typical examples in the real world include the dynamics of weather and temperature, of traffic, the way we meet our friends, etc. We take the rich tool set from probability theoryfor the analysis of Markov Chains and employ it to study a wide range of such distributed processes: Forest Fire Model (social networks), Balls-into-Bins with Deleting Bins, and fundamental consensus dynamics and protocols such as the Voter Model, 2-Choices, and 3-Majority
Dionigi, Pierfrancesco. "A random matrix theory approach to complex networks." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18513/.
Повний текст джерелаBuck, Micha Matthäus Verfasser], Frank [Akademischer Betreuer] Aurzada, and Thomas [Akademischer Betreuer] [Simon. "Exit problems for fractional processes, random walks and an insurance model / Micha Matthäus Buck ; Frank Aurzada, Thomas Simon." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1211478068/34.
Повний текст джерелаBuck, Micha Matthäus [Verfasser], Frank [Akademischer Betreuer] Aurzada, and Thomas [Akademischer Betreuer] Simon. "Exit problems for fractional processes, random walks and an insurance model / Micha Matthäus Buck ; Frank Aurzada, Thomas Simon." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1211478068/34.
Повний текст джерелаNeto, Milton Miranda. "Abordagem de martingais para análise assintótica do passeio aleatório do elefante." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/104/104131/tde-13112018-133355/.
Повний текст джерелаIn this work we study the elephant random walk introduced in (SCHUTZ; TRIMPER, 2004), a discrete time, non-Markovian stochastic process with unlimited range memory that presents phase transition. Our objective is to proof the almost sure convergence for the subcritical and critical regimes of the model. We also present a demonstration of the Central Limit Theorem for both regimes. For the supercritical regime we proof the convergence of the elephant random walk to a non-normal random variable based on the articles (BAUR; BERTOIN, 2016), (BERCU, 2018) and (COLETTI; GAVA; SCHUTZ, 2017b).
Sisto, Alessandro. "Geometric and probabilistic aspects of groups with hyperbolic features." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:bcf456c4-eef0-4fe8-bb7d-8b15f9cf7b18.
Повний текст джерелаKlumpp, Stefan. "Movements of molecular motors : diffusion and directed walks." Phd thesis, [S.l. : s.n.], 2003. http://pub.ub.uni-potsdam.de/2003/0020/klumpp.pdf.
Повний текст джерелаThomine, Damien. "Théorèmes limites pour les sommes de Birkhoff de fonctions d'intégrale nulle en théorie ergodique en mesure infinie." Thesis, Rennes 1, 2013. http://www.theses.fr/2013REN1S194/document.
Повний текст джерелаThis work is focused on some classes of ergodic dynamical systems endowed with an infinite invariant measure, such as transformations of the interval with a neutral fixed point or random walks. The asymptotic behavior of the Birkhoff sums of observables with a non-zero integral is well known, as long as the system shows some kind of hyperbolicity. The towers over a Gibbs-Markov map are especially interesting. In this context, we aim to study the case of observables whose integral is zero. We get the equivalent of a central limit theorem for some dynamical systems endowed with an infinite measure. After we introduce the necessary definitions, we adapt some results by E. Csáki and A. Földes on random walks to the case of Gibbs-Markov maps. We derive a theorem on the asymptotic independence of Birhoff sums, which is the core of this thesis, and from this point we work out a generalised central limit theorem. We also prove a few variations on this generalised central limit theorem. Then, we study dynamical systems in continuous time, such as semi-flows and flows. We first work on the asymptotic properties of the first return time and the local time for extensions of dynamical systems; this is done by spectral methods. Finally, step by step, we extend our generalised central limit theorem to cover some periodic flows, and in particular the geodesic flow on the unitary tangent bundle of some hyperbolic periodic manifolds
Albers, Tony. "Weak nonergodicity in anomalous diffusion processes." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-214327.
Повний текст джерелаAnomalous diffusion is a widespread transport mechanism, which is usually experimentally investigated by ensemble-based methods. Motivated by the progress in single-particle tracking, where time averages are typically determined, the question of ergodicity arises. Do ensemble-averaged quantities and time-averaged quantities coincide, and if not, in what way do they differ? In this thesis, we study different stochastic models for anomalous diffusion with respect to their ergodic or nonergodic behavior concerning the mean-squared displacement. We start our study with integrated Brownian motion, which is of high importance for all systems showing momentum diffusion. For this process, we contrast the ensemble-averaged squared displacement with the time-averaged squared displacement and, in particular, characterize the randomness of the latter. In the second part, we map integrated Brownian motion to other models in order to get a deeper insight into the origin of the nonergodic behavior. In doing so, we are led to a generalized Lévy walk. The latter reveals interesting phenomena, which have never been observed in the literature before. Finally, we introduce a new tool for analyzing anomalous diffusion processes, the distribution of generalized diffusivities, which goes beyond the mean-squared displacement, and we analyze with this tool an often used model of anomalous diffusion, the subdiffusive continuous time random walk
Triampo, Wannapong. "Non-Equilibrium Disordering Processes In binary Systems Due to an Active Agent." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26738.
Повний текст джерелаPh. D.
Maier, Benjamin F. "Spreading Processes in Human Systems." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/20950.
Повний текст джерелаHuman systems have been modeled and analyzed on the basis of complex networks theory in recent time. This abstraction allows for thorough quantitative analyses to investigate which structural and temporal features of a system influence the evolution of spreading processes, such as the passage of information or of infectious diseases. The first part of this work investigates how the ubiquitous modular hierarchical structure of static real-world networks allows for fast delivery of messages. New heuristics are developed to evaluate random walk mean first passage times and cover times on locally clustered networks. A comparison to average medium approximations shows that the emergence of these minima are pure network phenomena. It is further found that not all modular hierarchical network models provide optimal message delivery structure. In the second part, temporally varying face-to-face contact networks are investigated for their susceptibility to infection. Several studies have shown that people tend to spend time in small, densely-connected groups or in isolation, and that their connection behavior follows a circadian rhythm. To what extent both of these features influence the spread of diseases is as yet unclear. Therefore, a new temporal network model is devised here. Based on this model, circadially varying networks can for the first time be interpreted as following trajectories through a newly defined systemic state space. It is further revealed that in many temporally varying networks the system becomes less susceptible to infection when the time-scale of the disease approaches the time-scale of the network variation. This is in direct conflict with findings of other studies that predict increasing susceptibility of temporal networks, a discrepancy which is attributed to the invalidity of a widely applied approximation. The results presented here imply that new theoretical advances are necessary to study the spread of diseases in temporally varying networks.
Bringuier, Hugo. "Marches quantiques ouvertes." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30064/document.
Повний текст джерелаThis thesis is devoted to the study of stochastic models derived from open quantum systems. In particular, this work deals with open quantum walks that are the quantum analogues of classical random walks. The first part consists in giving a general presentation of open quantum walks. The mathematical tools necessary to study open quan- tum systems are presented, then the discrete and continuous time models of open quantum walks are exposed. These walks are respectively governed by quantum channels and Lindblad operators. The associated quantum trajectories are given by Markov chains and stochastic differential equations with jumps. The first part concludes with discussions over some of the research topics such as the Dirichlet problem for open quantum walks and the asymptotic theorems for quantum non demolition measurements. The second part collects the articles written within the framework of this thesis. These papers deal with the topics associated to the irreducibility, the recurrence-transience duality, the central limit theorem and the large deviations principle for continuous time open quantum walks
Faustino, Caio Leite. "Aspectos estatísticos em dinâmica de busca em ambientes escassos." Universidade Federal de Alagoas, 2009. http://repositorio.ufal.br/handle/riufal/1001.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
Neste trabalho, analisamos a dinâmica de busca e propriedades estatísticas de um organismo buscador ( searcher ) à procura de um alvo de interesse ( target ). De forma geral, muitos são os aspectos de interesse nesse tipo de estudo. Por exemplo, se pensarmos no contexto biológico, temos que na natureza constantemente organismos interagem uns com os outros, tanto dentro da mesma como entre diferentes espécies. Os objetivos gerais da busca aleatória são os mais variados, indo desde busca de alimentos, parceiro para reprodução etc, em seres vivos, até processos de interesse socio-econômicos, como busca por crianças desaparecidas, terroristas fugitivos ou então busca por petróleo. Em nosso modelo específico, consideramos o buscador e o alvo caminhando aleatoriamente numa rede unidimensional de tamanho e com condições periódicas de contorno. O tipo de difusão no sistema é determinado pela escolha da função de distribuição de probabilidade para os passos individuais dos indivíduos. Assumimos uma distribuição tipo lei de potência, característica de processos de Lévy . Considerando uma energia inicial do buscador , um gasto energético de caminhada e um ganho de energia g cada vez que o buscador encontra o alvo, discutimos algumas quantidades físicas relevantes, como flutuação energética, fração de buscadores sobreviventes e energia acumulada para N passos realizados - tempo de busca - como função de diferentes parâmetros, por exemplo, o comprimento de rede . Constatamos que o processo de busca com difusão balística é mais eficiente do que a Browniana, ocasionando a sobrevivência do organismo buscador em situações de densidade de alvos muito baixas. Este comportamento extremo garante a relativa sobrevivência do buscador. Também verificamos fortes evidências de uma transição contínua, para a qual numa dada fase temos sobrevivênvia e em outra temos extinção. Calculamos as densidades críticas que dependem dos parâmetros de difusão adotados pelos organismos. Também obtemos os expoentes críticos relacionados a tal transição. Nossos resultados sugerem uma universalidade dos expoentes críticos, que independente do tipo de difusão seguida pelos organismos.
Lauvergnat, Ronan. "Théorèmes limites pour des marches aléatoires markoviennes conditionnées à rester positives." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS451/document.
Повний текст джерелаWe consider a real random walk whose increments are constructed by a Markov chain definedon an abstract space. We suppose that the random walk is centred and that the dependence of the Markov walk in its past decreases exponentially fast (due to the spectral gap property). We study the first time when the random walk exits the positive half-line and prove that the asymptotic behaviour of the survey probability is inversely proportional to the square root of the time. We extend also to our Markovian model the following result of random walks with independent increments: the asymptotic law of the random walk renormalized and conditioned to stay positive is the Rayleigh law. Subsequently, we restrict our model to the cases when the Markov chain defining the increments of the random walk takes its values on a finite state space. Under this assumption and the condition that the walk is non-lattice, we complete our results giving local theorems for the random walk conditioned to stay positive. Finally, we apply these developments to branching processes under a random environment defined by a Markov chain taking its values on a finite state space. We give the asymptotic behaviour of the survey probability of the process in the critical case and the three subcritical cases (strongly, intermediate and weakly)
Levernier, Nicolas. "Temps de premier passage de processus non-markoviens." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066118/document.
Повний текст джерелаThe aim of this thesis is the evaluation of the first-passage time (FPT) of a non-markovian walker over a target. The first part is devoted to the computation of the mean first-passage time (MFPT) for different non-markovien confined processes, for which hidden variables are explicitly known. Our methodology, which adapts an existing formalism, relies on the determination of the distribution of the hidden variables at the instant of FPT. Then, we extend these ideas to the case of general non-markovian confined processes, without introducing the -often unkown- hidden variables. We show that the MFPT is entirely determined by the position of the walker in the future of the FPT. For gaussian walks with stationary increments, this position can be accurately described by a gaussian process, which enable to determine it self-consistently, and thus to find the MFPT. We apply this theory on many examples, in various dimensions. We show moreover that this theory is exact perturbatively around markovian processes. In the third part, we explore the influence of aging properties on the the FPT in confinement, and we predict the dependence of its statistic on geometric parameters. We verify these predictions on many examples. We show in particular that the non-linearity of the MFPT with the confinement is a hallmark of aging. Finally, we study some links between confined and unconfined problems. Our work suggests a promising way to evaluate the persistence exponent of non-markovian gaussian aging processes
Sales, Ludmilla Oliveira Ambrosi. "Testando a hipótese de passeio aleatório no mercado de ações brasileiro." reponame:Repositório Institucional do FGV, 2017. http://hdl.handle.net/10438/17960.
Повний текст джерелаRejected by Renata de Souza Nascimento (renata.souza@fgv.br), reason: Trabalho submetido duas vezes. on 2017-02-20T16:33:52Z (GMT)
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This paper revisits the theory of market efficiency and analyzes the Brazilian capital market for a more recent period in order to verify if the improvement pointed out in the study by Bonomo (2002) persists, that is, if the reduction of inefficiency in the course of the Time is robust. The existence of autocorrelation may be an indication of abnormal returns if the strategies adopted exploit this correlation and generate an abnormal return. The autocorrelation tests adopted in the random walk literature, for the most part, do not take into account the Heteroscedasticity characteristic of financial assets and, therefore, this work seeks to apply Bartlett’s formula for non-linear processes in order to verify if existence Of autocorrelation between the Brazilian papers analyzed and if this is enough to generate an extraordinary return. Traditional statistical and correlation tests were applied together with random walk tests to verify if the Brazilian capital market is efficient in its weak form.
Este trabalho revisita a teoria de eficiência de mercado e analisa o mercado de capitais brasileiros para um período mais recente a fim de verificar se a melhora apontada no estudo feito por Bonomo (2002) persiste, ou seja, se a redução da ineficiência no decorrer do tempo é robusta. Foram selecionadas 15 ações brasileiras que compunham o IBOVESPA de Maio 2016 e o período de análise compreende Janeiro de 2000 a Maio 2016. A existência de autocorrelação pode ser um indício de retornos anormais caso as estratégias adotadas explorem essa correlação e consigam gerar um retorno anormal. Os testes de autocorrelação adotados na literatura de passeio aleatório, em sua maioria, não levam em conta a característica de Heterocedasticidade dos ativos financeiros e, por isso, este trabalho busca aplicar a fórmula de Bartlett para processos não lineares a fim de verificar se a existência de autocorrelação entre os papéis brasileiros analisados e se esta é suficiente para gerar um retorno extraordinário. Testes estatísticos tradicionais e de correlação foram aplicados juntamente a testes de random walk para verificar se o mercado de capitais brasileiro é eficiente na sua forma fraca.
Wu, Tung-Lung Jr. "Linear and non-linear boundary crossing probabilities for Brownian motion and related processes." Applied Probability Trust - Journal of Applied Probability, 2010. http://hdl.handle.net/1993/8123.
Повний текст джерелаUtria, Valdes Jaime Antonio 1988. "Transição de fase para um modelo de percolação dirigida na árvore homogênea." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/307034.
Повний текст джерелаDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
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Abstract: The Abstract is available with the full electronic digital document
Mestrado
Estatistica
Mestre em Estatística
Moser, Martin [Verfasser], Robert [Akademischer Betreuer] Stelzer, Nina [Akademischer Betreuer] Gantert, and Gennady [Akademischer Betreuer] Samorodnitsky. "Extremal Behavior of Multivariate Mixed Moving Average Processes and of Random Walks with Dependent Increments / Martin Moser. Gutachter: Nina Gantert ; Gennady Samorodnitsky. Betreuer: Robert Stelzer." München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/1021499099/34.
Повний текст джерелаLam, Hoang Chuong. "Les théorèmes limites pour des processus stationnaires." Phd thesis, Université François Rabelais - Tours, 2012. http://tel.archives-ouvertes.fr/tel-00712572.
Повний текст джерелаLeichsenring, Alexandre Ribeiro. "Não monotonicidade do parâmetro crítico no modelo dos sapos." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-06042013-173920/.
Повний текст джерелаWe study a system of simple random walks on graphs, known as frog model. This model can be described generally speaking as follows: there are active and sleeping particles living on some graph G. Each particle performs a simple random walk with discrete time and at each moment it may disappear with probability 1 - p. When an active particle hits a sleeping particle, the latter becomes active and starts to perform, independently, a simple random walk on the graph. We present lower and upper bounds for the surviving critical parameter on the tree, and we show that this parameter is not a monotonic function of the graph it is defined on.
Duvernet, Laurent. "Analyse statistique des processus de marche aléatoire multifractale." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00567397.
Повний текст джерелаChiffaudel, Yann. "Etude de la diffusion des processus déterministes et faiblement aléatoires en environnement aléatoire." Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7083.
Повний текст джерелаThis thesis studies the diffusion in the mirrors model, a physics-based model introduced in 1988 by Ruijgrok and Cohen. This model is deterministic and reversible. To treat this difficult model, initially defined only in dimension 2, we first generalized it to a model valid in any dimension. Initial numerical studies suggested that the model is diffusive in dimensions greater than or equal to 3. We then explored a perturbative diffusion coefficient approach based on the lace expansion technique developed by Gordon Slade for the study of self-avoiding random walk. Faced with the difficulty of the calculations, we slightly simplified the model by giving up the reversibility constraint. We thus obtained a new model that we call the permutations model. We then transformed these two models into random walks in random environment using a systematic and general approach. Thanks to these modifications, we were able to push the perturbative approach to obtain a satisfactory approximation of the value of the diffusion coefficient in the permutations model. The main result is the existence of a series in which all terms are well defined and the first terms provide the desired approximation. The convergence of this series remains an open problem. The analytical results are supported by a numerical approach to these models, which shows that the lace expansion gives quality results. Many questions remain open, including the calculation of the following terms of perturbative development and the generalization of this approach to the mirrors model -which should not be a problem- and then to a broader class of models
De, Raphélis-Soissan Loïc. "Étude de marches aléatoires sur un arbre de Galton-Watson." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066056.
Повний текст джерелаThis work is devoted to the study of scaling limits of different functionals of random walks on a Galton-Watson tree, potentially in random environment. The randow walk we consider is a null recurrent nearest-neigbout random walk, the probability transition of which depend on the environment. More precisely, we study the trace of the walk, that is the sub-tree made up of the vertices visited by the walk. We first consider the case where in a certain sense the environment has finite variance, and we show that when well-renormalised, the trace converges towards the Brownian forest. We then consider hypotheses of regular variation on the environement, and we show that the height function of the walk (that is the sequence of heights in the tree of the walk) converges towards the continuous time height process of a spectrally positive strictly stable Lévy process, and that the trace of the walk converges towards the real tree coded by this very process. The strategy used to prove these two results is based on the study of a certain kind of trees that we introduce in this thesis: they are Galton-Watson trees with two types, one of which being sterile, and with edge lengths. Our main result about these trees states that their height functions satisfies an invariance principle, similar to that verified by simple Galton-Watson trees. These trees also find a direct application in multitype Galton-Watson trees with infinitely many types, as an explicit link between these two kind of trees allow us to show that they satisfy also the same invariance principle