L'objet de cette thèse est l'étude de l'auto-organisation dans les automates cellulaires unidimensionnels.Les automates cellulaires sont un système dynamique discret ainsi qu'un modèle de calcul massivement parallèle, ces deux aspects s'influençant mutuellement. L'auto-organisation est un phénomène où un comportement organisé est observé asymptotiquement, indépendamment de la configuration initiale. Typiquement, nous considérons que le point initial est tiré aléatoirement: étant donnée une mesure de probabilité décrivant une distribution de configurations initiales, nous étudions son évolution sous l'action de l'automate, le comportement asymptotique étant décrit par la(les) mesure(s) limite(s).Notre étude présente deux aspects. D'abord, nous caractérisons les mesures qui peuvent être atteintes à la limite par les automates cellulaires; ceci correspond aux différents comportements asymptotiques pouvant apparaître en simulation. Cette approche rejoint divers résultats récents caractérisant des paramètres de systèmes dynamiques par des conditions de calculabilité, utilisant des outils d'analyse calculable. Il s'agit également d'une description de la puissance de calcul des automates cellulaires sur les mesures.Ensuite, nous proposons des outils pour létude de l'auto-organisation dans des classes restreintes. Nous introduisons un cadre d'étude d'automates pouvant être vus comme un ensemble de particules en interaction, afin d'en déduire des propriétés sur leur comportement asymptotique. Une dernière direction de recherche concerne les automates convergeant vers la mesure uniforme sur une large classe de mesures initiales (phénomène de randomisation). / The subject of this thesis is the study of self-organization in one-dimensional cellular automata.Cellular automata are a discrete dynamical system as well as a massively parallel model of computation, both theseaspects influencing each other. Self-organisation is a phenomenon where an organised behaviour is observed asymptotically, regardless of the initial configuration. Typically, we consider that the initial point is sampled at random; that is, we consider a probability measure describing the distribution of theinitial configurations, and we study its evolution under the action of the automaton, the asymptoticbehaviour being described by the limit measure(s).Our work is two-sided. On the one hand, we characterise measures that can bereached as limit measures by cellular automata; this corresponds to the possible kinds of asymptoticbehaviours that can arise in simulations. This approach is similar to several recent results characterising someparameters of dynamical systems by computability conditions, using tools from computable analysis. Thisresult is also a description of the measure-theoretical computational power of cellular automata.On the other hand, we provided tools for the practical study of self-organization in restricted classes of cellularautomata. We introduced a frameworkfor cellular automata that can be seen as a set of interacting particles, in order todeduce properties concerning their asymptotic behaviour. Another ongoing research direction focus on cellular automata that converge to the uniform measurefor a wide class of initial measures (randomization phenomenon).

[pt] Provamos que campos de vetores C1- genéricos em uma variedade compacta não possuem probabilidades invariantes absolutamente contínuas em relação a uma medida de volume. Este trabalho estende ao caso de tempo contínuo um resultado de Avila e Bochi. / [en] We prove that C1-generic vector fields in a compact manifold do not have absolutely continuous invariant probabilities. This extends a result of Avila and Bochi to the continuous time case.

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Thermostated time evolutions are on a firm ground and widely used in classical molecular dynamics (MD) simulations. Hamilton´s equations of motion are supplemented by time-dependent pseudofriction terms that convert the microcanonical isoenergetic time evolution into a canonical isothermal time evolution, thus permitting the calculation of canonical ensemble averages by time averaging. However, similar methods for quantum MD schemes are still lacking. Given the rich dynamical behavior of ultracold trapped quantum gases depending on the value of the s-wave scattering length, it is timely to investigate how classical thermostating methods can be combined with powerful approximate quantum dynamics schemes to deal with interacting quantum systems at finite temperature. In this work, the popular method of Nose and Hoover to create canonically distributed positions and momenta in classical MD simulations is generalized to a genuine quantum system of infinite dimensionality. We show that for the quantum harmonic oscillator, the equations of motion in terms of coherent states may be modified in a Nose-Hoover manner to mimic the coupling of the system to a thermal bath and create a quantum canonical ensemble. The method is developed initially for a single particle and then generalized to the case of an arbitrary number of identical quantum particles, involving entangled distribution functions. The resulting isothermal equations of motion for bosons and fermions contain additional terms leading to Bose-attraction and Pauli-blocking, respectively. Questions of ergodicity are discussed for different coupling schemes. In the many-particle case, the superiority of the Nose-Hoover technique to a Langevin approach is demonstrated. In addition, the work contains an investigation of the Grilli-Tosatti thermostating method applied to the harmonic oscillator, and calculations for quantum wavefunctions moving with a time-invariant shape in a harmonic potential.

Les jeux stochastiques à somme nulle possèdent une structure récursive qui s'exprime dans leur opérateur de programmation dynamique, appelé opérateur de Shapley. Ce dernier permet d'étudier le comportement asymptotique de la moyenne des paiements par unité de temps. En particulier, le paiement moyen existe et ne dépend pas de l'état initial si l'équation ergodique - une équation non-linéaire aux valeurs propres faisant intervenir l'opérateur de Shapley - admet une solution. Comprendre sous quelles conditions cette équation admet une solution est un problème central de la théorie de Perron-Frobenius non-linéaire, et constitue le principal thème d'étude de cette thèse. Diverses classes connues d'opérateur de Shapley peuvent être caractérisées par des propriétés basées entièrement sur la relation d'ordre ou la structure métrique de l'espace. Nous étendons tout d'abord cette caractérisation aux opérateurs de Shapley "sans paiements", qui proviennent de jeux sans paiements instantanés. Pour cela, nous établissons une expression sous forme minimax des fonctions homogènes de degré un et non-expansives par rapport à une norme faible de Minkowski. Nous nous intéressons ensuite au problème de savoir si l'équation ergodique a une solution pour toute perturbation additive des paiements, problème qui étend la notion d'ergodicité des chaînes de Markov. Quand les paiements sont bornés, cette propriété d'"ergodicité" est caractérisée par l'unicité, à une constante additive près, du point fixe d'un opérateur de Shapley sans paiement. Nous donnons une solution combinatoire s'exprimant au moyen d'hypergraphes à ce problème, ainsi qu'à des problèmes voisins d'existence de points fixes. Puis, nous en déduisons des résultats de complexité. En utilisant la théorie des opérateurs accrétifs, nous généralisons ensuite la condition d'hypergraphes à tous types d'opérateurs de Shapley, y compris ceux provenant de jeux dont les paiements ne sont pas bornés. Dans un troisième temps, nous considérons le problème de l'unicité, à une constante additive près, du vecteur propre. Nous montrons d'abord que l'unicité a lieu pour une perturbation générique des paiements. Puis, dans le cadre des jeux à information parfaite avec un nombre fini d'actions, nous précisons la nature géométrique de l'ensemble des perturbations où se produit l'unicité. Nous en déduisons un schéma de perturbations qui permet de résoudre les instances dégénérées pour l'itération sur les politiques. / Zero-sum stochastic games have a recursive structure encompassed in their dynamic programming operator, so-called Shapley operator. The latter is a useful tool to study the asymptotic behavior of the average payoff per time unit. Particularly, the mean payoff exists and is independent of the initial state as soon as the ergodic equation - a nonlinear eigenvalue equation involving the Shapley operator - has a solution. The solvability of the latter equation in finite dimension is a central question in nonlinear Perron-Frobenius theory, and the main focus of the present thesis. Several known classes of Shapley operators can be characterized by properties based entirely on the order structure or the metric structure of the space. We first extend this characterization to "payment-free" Shapley operators, that is, operators arising from games without stage payments. This is derived from a general minimax formula for functions homogeneous of degree one and nonexpansive with respect to a given weak Minkowski norm. Next, we address the problem of the solvability of the ergodic equation for all additive perturbations of the payment function. This problem extends the notion of ergodicity for finite Markov chains. With bounded payment function, this "ergodicity" property is characterized by the uniqueness, up to the addition by a constant, of the fixed point of a payment-free Shapley operator. We give a combinatorial solution in terms of hypergraphs to this problem, as well as other related problems of fixed-point existence, and we infer complexity results. Then, we use the theory of accretive operators to generalize the hypergraph condition to all Shapley operators, including ones for which the payment function is not bounded. Finally, we consider the problem of uniqueness, up to the addition by a constant, of the nonlinear eigenvector. We first show that uniqueness holds for a generic additive perturbation of the payments. Then, in the framework of perfect information and finite action spaces, we provide an additional geometric description of the perturbations for which uniqueness occurs. As an application, we obtain a perturbation scheme allowing one to solve degenerate instances of stochastic games by policy iteration.

This book is devoted to the study of operators on discrete structures. The operators are supposed to be self-adjoint and obey a certain translation invariance property. The discrete structures are given as Cayley graphs via finitely generated groups. Here, sofic groups and amenable groups are in the center of our considerations. Note that every finitely generated amenable group is sofic. We investigate the spectrum of a discrete self-adjoint operator by studying a sequence of finite dimensional analogues of these operators. In the setting of amenable groups we obtain these approximating operators by restricting the operator in question to finite subsets Qn , n ∈ N. These finite dimensional operators are self-adjoint and therefore admit a well-defined normalized eigenvalue counting function. The limit of the normalized eigenvalue counting functions when |Qn | → ∞ (if it exists) is called the integrated density of states (IDS). It is a distribution function of a probability measure encoding the distribution of the spectrum of the operator in question on the real axis. We prove the existence of the IDS in various geometric settings and for different types of operators. The models we consider include deterministic as well as random situations. Depending on the specific setting, we prove existence of the IDS as a weak limit of distribution functions or even as a uniform limit. Moreover, in certain situations we are able to express the IDS via a semi-explicit formula using the trace of the spectral projection of the original operator. This is sometimes referred to as the validity of the Pastur-Shubin trace formula. In the most general geometric setting we study, the operators are defined on Cayley graphs of sofic groups. Here we prove weak convergence of the eigenvalue counting functions and verify the validity of the Pastur-Shubin trace formula for random and non-random operators . These results apply to operators which not necessarily bounded or of finite hopping range. The methods are based on resolvent techniques. This theory is established without having an ergodic theorem for sofic groups at hand. Note that ergodic theory is the usual tool used in the proof of convergence results of this type. Specifying to operators on amenable groups we are able to prove stronger results. In the discrete case, we show that the IDS exists uniformly for a certain class of finite hopping range operators. This is obtained by using a Banach space-valued ergodic theorem. We show that this applies to eigenvalue counting functions, which implies their convergence with respect to the Banach space norm, in this case the supremum norm. Thus, the heart of this theory is the verification of the Banach space-valued ergodic theorem. Proceeding in two steps we first prove this result for so-called ST-amenable groups. Then, using results from the theory of ε-quasi tilings, we prove a version of the Banach space-valued ergodic theorem which is valid for all amenable groups. Focusing on random operators on amenable groups, we prove uniform existence of the IDS without the assumption that the operator needs to be of finite hopping range or bounded. Moreover, we verify the Pastur-Shubin trace formula. Here we present different techniques. First we show uniform convergence of the normalized eigenvalue counting functions adapting the technique of the Banach space-valued ergodic theorem from the deterministic setting. In a second approach we use weak convergence of the eigenvalue counting functions and additionally obtain control over the convergence at the jumps of the IDS. These ingredients are applied to verify uniform existence of the IDS. In both situations we employ results from the theory of large deviations, in order to deal with long-range interactions.

Many complexity measures are defined as the size of a minimal representation in a specific model class. One such complexity measure, which is important because it is widely applied, is statistical complexity. It is defined for discrete-time, stationary stochastic processes within a theory called computational mechanics. Here, a mathematically rigorous, more general version of this theory is presented, and abstract properties of statistical complexity as a function on the space of processes are investigated. In particular, weak-* lower semi-continuity and concavity are shown, and it is argued that these properties should be shared by all sensible complexity measures. Furthermore, a formula for the ergodic decomposition is obtained. The same results are also proven for two other complexity measures that are defined by different model classes, namely process dimension and generative complexity. These two quantities, and also the information theoretic complexity measure called excess entropy, are related to statistical complexity, and this relation is discussed here. It is also shown that computational mechanics can be reformulated in terms of Frank Knight''s prediction process, which is of both conceptual and technical interest. In particular, it allows for a unified treatment of different processes and facilitates topological considerations. Continuity of the Markov transition kernel of a discrete version of the prediction process is obtained as a new result.

[pt] Os expoentes de Lyapunov são uma ferramenta bastante utilizada quando busca-se entender o comportamento de sistemas dinâmicos, em particular de cociclos lineares. De fato, concentramo-nos no expoente maximal, pois este determina o comportamento geral do sistema, de modo que sua positividade pode ser um indicativo de que estamos lidando com um sistema caótico. Nesse sentido estudamos um teorema provado por Michael Herman, que fornece uma cota inferior para o expoente de Lyapunov maximal de uma classe de cociclos lineares definidos por rotações no círculo. A prova deste resultado utiliza um processo de complexificação do cociclo e um argumento de subharmonicidade. Surpreendentemente, essa cota inferior é na verdade uma identidade, o que foi provado posteriormente por Avila e Bochi. Como será mostrado nesta dissertação, o argumento para obter a identidade depende crucialmente da harmonicidade, e não da mera subharmonicidade de certas funções associadas às iterações do cociclo. / [en] Lyapunov exponents are a widely used tool when trying to understand the behavior of dynamical systems in general, and in particular that of linear cocycles. We focus on the maximal exponent, as it determines the general behavior of the system, in that its positivity can be an indication that we are dealing with a chaotic system. In this sense, we study a theorem obtained by Michael Herman, providing a lower bound on the maximal Lyapunov exponent of a class of linear cocycles defined by circle rotations. The proof of this result employs the complexification of the cocycle and an argument based on subharmonicity. Surprisingly, this lower bound is in fact an identity, which was proven later by Avila and Bochi. As it will be shown in this dissertation, the argument for obtaining this identity depends crucially on the harmonicity, as opposed to the mere subharmonicity of certain functions associated with the iterates of the cocycle.

[ES] El objetivo principal de esta tesis es el estudio de diferentes propiedades (principalmente ergódicas) de operadores de composición y de composición ponderados actuando en espacios de funciones holomorfas definidas en un espacio de Banach de dimensión infinita. Sea X un espacio de Banach y U un subconjunto abierto. Dada una aplicación φ : U → U, la acción f 7 → Cφ ( f ) = f ◦ φ define un operador, llamado operador de composición (y a φ se le llama símbolo del operador). Consideramos este operador actuando en diferentes espacios de funciones. La filosofía general es intentar caracterizar en cada caso las propiedades de nuestro interés en función de condiciones en φ. También, dada ψ: U → C, el operador de multiplicación se define como Mψ( f ) = ψ · f y (con φ como antes), el operador de composición ponderado como Cψ,φ ( f ) = ψ·( f ◦φ) (en este caso ψ se conoce como el peso o multiplicador del operador). Nuevamente, la idea es describir propiedades de estos operadores en términos de condiciones sobre φ y/o ψ. Claramente Cψ,φ = Mψ ◦ Cφ , y tomando φ = idU (la identidad en U) o ψ ≡ 1 (la función constante 1) recuperamos Mψ y Cφ . Denotamos con B a la bola unidad abierta de X . El espacio de funciones holomorfas f : B → C se denota H(B). Escribimos Hb(B) para el espacio de funciones holomorfas en B de tipo acotado y H∞(B) para el espacio de funciones holomorfas y acotadas en B. Vamos a considerar operadores de composición y de composición ponderados definidos en cada uno de estos espacios (tomando entonces U = B en la definición). También consideramos operadores de composición definidos en el espacio vectorial de polinomios continuos y m-homogéneos (denotado P (m X )). En este caso tomamos U = X . La tesis consta de cinco capítulos. En el Capítulo 1 damos las definiciones y resultados básicos necesarios para que el texto sea autocontenido. En el Capítulo 2 tratamos con operadores de composición ergódicos en media y acotados en potencias definidos en P (m X ). En el Capítulo 3 estudiamos operadores de composición ergódicos en media y acotados en potencias definidos en H(B), Hb(B) y H∞(B); tratando también el caso particular en que B es la bola de un espacio de Hilbert. En el Capítulo 4 estudiamos la compacidad de operadores de composición ponderados definidos en H∞(B), así como la acotación, reflexividad, cuándo es Montel y la compacidad (débil) en Hb(B). Finalmente, en el Capítulo 5 obtenemos resultados sobre la acotación en potencias y ergodicidad en media de operadores de composición ponderados actuando en H(B), Hb(B) y H∞(B); así como sobre compacidad y ergodicidad en media del operador de multiplicación. / [CA] L’objectiu principal d’aquesta tesi és l’estudi de diferents propietats (principalment ergòdiques) d’operadors de composició i de composició ponderats actuant en espais de funcions holomorfes en un espai de Banach de dimensió infinita. Siga X un espai de Banach i U un subconjunt obert. Donada una aplicació φ : U → U, l’acció f 7 → Cφ ( f ) = f ◦ φ defineix un operador, anomenat operador de compo- sició (i φ s’anomena símbol de l’operador). Considerem aquest operador actuant en diferents espais de funcions. La filosofia general és intentar caracteritzar en cada cas les propietats del nostre interés en funció de condicions en φ. També, donada ψ: U → C, l’operador de multiplicació es defineix com a Mψ( f ) = ψ · f i (amb φ com abans), l’operador de composició ponderat com a Cψ,φ ( f ) = ψ · ( f ◦ φ) (en aquest cas ψ es coneix com el pes o multiplicador de l’operador). Novament, la idea és descriure propietats d’aquests operadors en termes de condicions sobre φ i/o ψ. Clarament Cψ,φ = Mψ ◦ Cφ , i prenent φ = idU (la identitat en U) o ψ ≡ 1 (la funció constant 1) recuperem Mψ i Cφ . Denotem per B la bola unitat oberta d’X . L’espai de funcions holomorfes f : B → C es denota H(B). Escrivim Hb(B) per a l’espai de funcions holomorfes en B de tipus fitat i H∞(B) per a l’espai de funcions holomorfes i fitades en B. Anem a considerar ope- radors de composició i de composició ponderats definits en cadascun d’aquests espais (prenent llavors U = B en la definició). També considerem operadors de composició definits en l’espai vectorial de polinomis continus i m-homogenis (denotat P (m X )). En aquest cas prenem U = X . La tesi consta de cinc capítols. En el Capítol 1 donem les definicions i resultats bàsics necessaris perquè el text siga autocontingut. En el Capítol 2 tractem amb ope- radors de composició ergòdics en mitjana i fitats en potències definits en P (m X ). En el Capítol 3 estudiem operadors de composició ergòdics en mitjana i fitats en potències definits en H(B), Hb(B) i H∞(B); tractant també el cas particular en que B és la bola d’un espai de Hilbert. En el Capítol 4 estudiem la compacitat d’operadors de composi- ció ponderats definits en H∞(B), així com també la fitació, reflexivitat, quan és Montel i la compacitat (feble) en Hb(B). Finalment, en el Capítol 5 obtenim resultats sobre la fitació en potències i ergodicitat en mitjana d’operadors de composició ponderats actuant en H(B), Hb(B) i H∞(B); així com també sobre compacitat i ergodicitat en mitjana de l’operador de multiplicació. / [EN] The main aim in this thesis is to study different properties (mostly ergodic) of compo- sition and weighted composition operators acting on spaces of holomorphic functions defined on an infinite dimensional complex Banach space. Let X be a Banach space and U some open subset. Given a mapping φ : U → U the action f 7 → Cφ ( f ) = f ◦ φ defines an operator, called composition operator (and φ is called the symbol of the operator). We consider this operator acting on different spaces of functions. The general philosophy is to try to characterise in each case the properties of our interest in terms of conditions on φ. Also, given ψ: U → C the multiplication operator is defined as Mψ( f ) = ψ· f and (with φ as above), the weighted composition operator as Cψ,φ ( f ) = ψ · ( f ◦ φ) (here ψ is called the weight or multiplier of the operator). Again, the idea is to describe properties of these operators in terms of conditions on ψ and/or φ. Clearly Cψ,φ = Mψ ◦ Cφ , and taking φ = idU (the identity on U) or ψ ≡ 1 (the constant function 1) we recover Mψ and Cφ . We denote the open unit ball of X by B. The space of all holomorphic functions f : B → C is denoted by H(B). We write Hb(B) for the space holomorphic functions of bounded type on B, and H∞(B) for the space of bounded holomorphic functions on B. We are going to consider composition and weighted composition operators defined on each one of these spaces (taking then U = B in the definition). We also consider composition operators defined on the vector space of all continuous m-homogeneous polynomials on X (which is denoted by P (m X )). In this case we take U = X . The thesis consists of 5 chapters. In Chapter 1 we introduce definitions and ba- sic results, needed to make the text self-contained. In Chapter 2 we deal with mean ergodic and power bounded composition operators defined on P (m X ). In Chapter 3 we study mean ergodic and power bounded composition operators defined on H(B), Hb(B) and H∞(B); considering also the particular case when B is the ball of a Hilbert space. In Chapter 4 we study compactness of weighted composition operators defined on H∞(B), as well as boundedness, reflexivity, being Montel and (weak) compactness on Hb(B). Finally, in Chapter 5 we obtain different results about power bounded- ness and mean ergodicity of weighted composition operators acting on H(B), Hb(B) and H∞(B), as well as about compactness and mean ergodicity of the multiplication operator. / Santacreu Ferra, D. (2022). Composition Operators on Classes of Holomorphic Functions on Banach Spaces [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/185235 / TESIS

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