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## Singular Perturbation for the Discounted Continuous Control of Piecewise Deterministic Markov Processes

Costa, Oswaldo Luiz do Valle; DUFOUR, F.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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This paper deals with the expected discounted continuous control of piecewise deterministic Markov processes (PDMP`s) using a singular perturbation approach for dealing with rapidly oscillating parameters. The state space of the PDMP is written as the product of a finite set and a subset of the Euclidean space a""e (n) . The discrete part of the state, called the regime, characterizes the mode of operation of the physical system under consideration, and is supposed to have a fast (associated to a small parameter epsilon > 0) and a slow behavior. By using a similar approach as developed in Yin and Zhang (Continuous-Time Markov Chains and Applications: A Singular Perturbation Approach, Applications of Mathematics, vol. 37, Springer, New York, 1998, Chaps. 1 and 3) the idea in this paper is to reduce the number of regimes by considering an averaged model in which the regimes within the same class are aggregated through the quasi-stationary distribution so that the different states in this class are replaced by a single one. The main goal is to show that the value function of the control problem for the system driven by the perturbed Markov chain converges to the value function of this limit control problem as epsilon goes to zero. This convergence is obtained by...

## Statistical Analysis of Notational AFL Data Using Continuous Time Markov Chains

Meyer, Denny; Forbes, Don; Clarke, Stephen R.
Fonte: Asist Group Publicador: Asist Group
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
79.317827%
Animal biologists commonly use continuous time Markov chain models to describe patterns of animal behaviour. In this paper we consider the use of these models for describing AFL football. In particular we test the assumptions for continuous time Markov chain models (CTMCs), with time, distance and speed values associated with each transition. Using a simple event categorisation it is found that a semi-Markov chain model is appropriate for this data. This validates the use of Markov Chains for future studies in which the outcomes of AFL matches are simulated.

## Problèmes de premier passage et de commande optimale pour des chaînes de Markov à temps discret.

Kounta, Moussa
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
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Nous considérons des processus de diffusion, déﬁnis par des équations différentielles stochastiques, et puis nous nous intéressons à des problèmes de premier passage pour les chaînes de Markov en temps discret correspon- dant à ces processus de diffusion. Comme il est connu dans la littérature, ces chaînes convergent en loi vers la solution des équations différentielles stochas- tiques considérées. Notre contribution consiste à trouver des formules expli- cites pour la probabilité de premier passage et la durée de la partie pour ces chaînes de Markov à temps discret. Nous montrons aussi que les résultats ob- tenus convergent selon la métrique euclidienne (i.e topologie euclidienne) vers les quantités correspondantes pour les processus de diffusion. En dernier lieu, nous étudions un problème de commande optimale pour des chaînes de Markov en temps discret. L’objectif est de trouver la valeur qui mi- nimise l’espérance mathématique d’une certaine fonction de coût. Contraire- ment au cas continu, il n’existe pas de formule explicite pour cette valeur op- timale dans le cas discret. Ainsi, nous avons étudié dans cette thèse quelques cas particuliers pour lesquels nous avons trouvé cette valeur optimale.; We consider diffusion processes...

## Long-Range Dependence of Markov Processes

Carpio, Kristine Joy Espiritu
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
Português
Relevância na Pesquisa
79.62264%
Long-range dependence in discrete and continuous time Markov chains over a countable state space is defined via embedded renewal processes brought about by visits to a fixed state. In the discrete time chain, solidarity properties are obtained and long-range dependence of functionals are examined. On the other hand, the study of LRD of continuous time chains is defined via the number of visits in a given time interval. Long-range dependence of Markov chains over a non-countable state space is also carried out through positive Harris chains. Embedded renewal processes in these chains exist via visits to sets of states called proper atoms. ¶ Examples of these chains are presented, with particular attention given to long-range dependent Markov chains in single-server queues, namely, the waiting times of GI/G/1 queues and queue lengths at departure epochs in M/G/1 queues. The presence of long-range dependence in these processes is dependent on the moment index of the lifetime distribution of the service times. The Hurst indexes are obtained under certain conditions on the distribution function of the service times and the structure of the correlations. These processes of waiting times and queue sizes are also examined in a range of M/P/2 queues via simulation (here...

## Comparisons for backward stochastic differential equations on Markov chains and related no-arbitrage conditions

Cohen, S.; Elliott, R.
Fonte: Inst Mathematical Statistics Publicador: Inst Mathematical Statistics
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
89.03777%
Most previous contributions to BSDEs, and the related theories of nonlinear expectation and dynamic risk measures, have been in the framework of continuous time diffusions or jump diffusions. Using solutions of BSDEs on spaces related to finite state, continuous time Markov chains, we develop a theory of nonlinear expectations in the spirit of [Dynamically consistent nonlinear evaluations and expectations (2005) Shandong Univ.]. We prove basic properties of these expectations and show their applications to dynamic risk measures on such spaces. In particular, we prove comparison theorems for scalar and vector valued solutions to BSDEs, and discuss arbitrage and risk measures in the scalar case.; Samuel N. Cohen and Robert J. Elliott

## Parameter estimation for discretely observed continuous-time Markov chains

Cramer, Roxy D.
Português
Relevância na Pesquisa
89.39799%
This thesis develops a method for estimating the parameters of continuous-time Markov chains discretely observed by Poisson sampling. The inference problem in this context is usually simplified by assuming the process to be time-homogeneous and that the process can be observed continuously for some observation period. But many real problems are not homogeneous; moreover, in practice it is often difficult to observe random processes continuously. In this work, the Dynkin Identity motivates a martingale estimating equation which is no more complicated a function of the parameters than the infinitesimal generator of the chain. The time-dependent generators of inhomogeneous chains therefore present no new obstacles. The Dynkin Martingale estimating equation derived here applies to processes discretely observed according to an independent Poisson process. Random observation of this kind alleviates the so-called aliasing problem, which can arise when continuous-time processes are observed discretely. Theoretical arguments exploit the martingale structure to obtain conditions ensuring strong consistency and asymptotic normality of the estimators. Simulation studies of a single-server Markov queue with sinusoidal arrivals test the performance of the estimators under different sampling schemes and against the benchmark maximum likelihood estimators based on continuous observation.

## Transient Reward Approximation for Continuous-Time Markov Chains

Hahn, Ernst Moritz; Hermanns, Holger; Wimmer, Ralf; Becker, Bernd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
89.09089%
We are interested in the analysis of very large continuous-time Markov chains (CTMCs) with many distinct rates. Such models arise naturally in the context of reliability analysis, e.g., of computer network performability analysis, of power grids, of computer virus vulnerability, and in the study of crowd dynamics. We use abstraction techniques together with novel algorithms for the computation of bounds on the expected final and accumulated rewards in continuous-time Markov decision processes (CTMDPs). These ingredients are combined in a partly symbolic and partly explicit (symblicit) analysis approach. In particular, we circumvent the use of multi-terminal decision diagrams, because the latter do not work well if facing a large number of different rates. We demonstrate the practical applicability and efficiency of the approach on two case studies.; Comment: Accepted for publication in IEEE Transactions on Reliability

## A Ruelle Operator for continuous time Markov Chains

Baraviera, Alexandre; Exel, Ruy; Lopes, Artur O.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
79.013535%
We consider a generalization of the Ruelle theorem for the case of continuous time problems. We present a result which we believe is important for future use in problems in Mathematical Physics related to $C^*$-Algebras We consider a finite state set $S$ and a stationary continuous time Markov Chain $X_t$, $t\geq 0$, taking values on S. We denote by $\Omega$ the set of paths $w$ taking values on S (the elements $w$ are locally constant with left and right limits and are also right continuous on $t$). We consider an infinitesimal generator $L$ and a stationary vector $p_0$. We denote by $P$ the associated probability on ($\Omega, {\cal B}$). This is the a priori probability. All functions $f$ we consider bellow are in the set ${\cal L}^\infty (P)$. From the probability $P$ we define a Ruelle operator ${\cal L}^t, t\geq 0$, acting on functions $f:\Omega \to \mathbb{R}$ of ${\cal L}^\infty (P)$. Given $V:\Omega \to \mathbb{R}$, such that is constant in sets of the form $\{X_0=c\}$, we define a modified Ruelle operator $\tilde{{\cal L}}_V^t, t\geq 0$. We are able to show the existence of an eigenfunction $u$ and an eigen-probability $\nu_V$ on $\Omega$ associated to $\tilde{{\cal L}}^t_V, t\geq 0$. We also show the following property for the probability $\nu_V$: for any integrable $g\in {\cal L}^\infty (P)$ and any real and positive $t$ $$\int e^{-\int_0^t (V \circ \Theta_s)(.) ds} [ (\tilde{{\cal L}}^t_V (g)) \circ \theta_t ] d \nu_V = \int g d \nu_V$$ This equation generalize...

## Non-equilibrium thermodynamic potentials for continuous-time Markov chains

Verley, Gatien
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
88.83126%
We connect the rare fluctuations of an Equilibrium (EQ) process to the typical fluctuations of a Non-Equilibrium (NE) stationary process. In the framework of large deviation theory, this observation allows us to introduce NE thermodynamic potentials. For continuous-time Markov chains, we identify the relevant pairs of conjugated variables and propose two NE ensembles: one with fixed dynamics and fluctuating time-averaged variables, and another with fixed time-averaged variables, but a fluctuating dynamics. Accordingly, we show that NE processes are equivalent to conditioned EQ processes ensuring that NE potentials are Legendre dual. We find a variational principle satisfied by the NE potentials that reach their maximum in the NE stationary state and whose first derivatives produce the NE equations of state, and second derivatives produce the NE Maxwell relations generalizing the Onsager reciprocity relations.; Comment: 16 pages, 2 tables, 2 figures

## Erratum to: Model-checking continuous-time Markov chains by Aziz et al

Jansen, David N.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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This note corrects a discrepancy between the semantics and the algorithm of the multiple until operator of CSL, like in Pr_{> 0.0025} (a until[1,2] b until[3,4] c), of the article: Model-checking continuous-time Markov chains by Aziz, Sanwal, Singhal and Brayton, TOCL 1(1), July 2000, pp. 162-170.

## Risk-sensitive control of continuous time Markov chains

Ghosh, Mrinal K.; Saha, Subhamay
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
88.88704%
We study risk-sensitive control of continuous time Markov chains taking values in discrete state space. We study both finite and infinite horizon problems. In the finite horizon problem we characterise the value function via HJB equation and obtain an optimal Markov control. We do the same for infinite horizon discounted cost case. In the infinite horizon average cost case we establish the existence of an optimal stationary control under certain Lyapunov condition. We also develop a policy iteration algorithm for finding an optimal control.; Comment: 19 pages, Stochastics, 2014

## A thermodynamic formalism for continuous time Markov chains with values on the Bernoulli Space: entropy, pressure and large deviations

Lopes, Artur O.; Neumann, Adriana; Thieullen, Philippe
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
89.53037%
Through this paper we analyze the ergodic properties of continuous time Markov chains with values on the one-dimensional spin lattice 1,...,d}^N (also known as the Bernoulli space). Initially, we consider as the infinitesimal generator the operator $L={\mc L}_A -I$, where \mc L_A is a discrete time Ruelle operator (transfer operator), and A:{1,...,d}^N \to R is a given fixed Lipschitz function. The associated continuous time stationary Markov chain will define the\emph{a priori}probability. Given a Lipschitz interaction V:\{1,...,d\}^{\bb N}\to \mathbb{R}, we are interested in Gibbs (equilibrium) state for such $V$. This will be another continuous time stationary Markov chain. In order to analyze this problem we will use a continuous time Ruelle operator (transfer operator) naturally associated to V. Among other things we will show that a continuous time Perron-Frobenius Theorem is true in the case V is a Lipschitz function. We also introduce an entropy, which is negative, and we consider a variational principle of pressure. Finally, we analyze large deviations properties for the empirical measure in the continuous time setting using results by Y. Kifer.; Comment: to appear Journ. of Stat. Physics

## Joint density for the local times of continuous-time Markov chains: Extended version

Brydges, D.; van der Hofstad, R.; Konig, W.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
78.98182%
We investigate the local times of a continuous-time Markov chain on an arbitrary discrete state space. For fixed finite range of the Markov chain, we derive an explicit formula for the joint density of all local times on the range, at any fixed time. We use standard tools from the theory of stochastic processes and finite-dimensional complex calculus. We apply this formula in the following directions: (1) we derive large deviation upper estimates for the normalized local times beyond the exponential scale, (2) we derive the upper bound in Varadhan's \chwk{l}emma for any measurable functional of the local times, \ch{and} (3) we derive large deviation upper bounds for continuous-time simple random walk on large subboxes of $\Z^d$ tending to $\Z^d$ as time diverges. We finally discuss the relation of our density formula to the Ray-Knight theorem for continuous-time simple random walk on $\Z$, which is analogous to the well-known Ray-Knight description of Brownian local times. In this extended version, we prove that the Ray-Knight theorem follows from our density formula.; Comment: 22 pages

## A Comment on the Book "Continuous-Time Markov Chains" by W.J. Anderson

Chen, Mu-Fa
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
88.71142%
The book "Continuous-Time Markov Chains" by W. J. Anderson collects a large part of the development in the past thirty years. It is now a popular reference for the researchers on this subject or related fields. Unfortunately, due to a misunderstanding of the approximating methods, several results in the book are incorrectly stated or proved. Since the results are related to the present author's work, to whom it may be a duty to correct the mistakes in order to avoid further confusion. We emphasize the approximating methods because they are useful in many situations.; Comment: In the past twenty years or more, we have seen several times that some results from the book under review are either incorrectly used or cited. The uploaded older paper may be helpful to classify some confusions. Two footnotes are newly added

## Cycle symmetries and circulation fluctuations for discrete-time and continuous-time Markov chains

Jia, Chen; Jiang, Daquan; Qian, Minping
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
89.15762%
In probability theory, equalities are much less than inequalities. In this paper, we find a series of equalities which characterize the symmetry of the forming times of a family of similar cycles for discrete-time and continuous-time Markov chains. Moreover, we use these cycle symmetries to study the circulation fluctuations for Markov chains. We prove that the empirical circulations of a family of cycles passing through a common state satisfy a large deviation principle with a rate function which has an highly non-obvious symmetry. Finally, we discuss the applications of our work in statistical physics and biochemistry.; Comment: 30 pages, 1 figure

## Weak Error for Continuous Time Markov Chains Related to Fractional in Time P(I)DEs

Kelbert, M.; Konakov, V.; Menozzi, S.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
88.86219%
We provide sharp error bounds for the difference between the transition densities of some multidimensional Continuous Time Markov Chains (CTMC) and the fundamental solutions of some fractional in time Partial (Integro) Differential Equations (P(I)DEs). Namely, we consider equations involving a time fractional derivative of Caputo type and a spatial operator corresponding to the generator of a non degenerate Brownian or stable driven Stochastic Differential Equation (SDE).; Comment: 36 pages

## Optimization-based Lyapunov function construction for continuous-time Markov chains with affine transition rates

Milias-Argeitis, Andreas; Khammash, Mustafa
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
88.71142%
We address the problem of Lyapunov function construction for a class of continuous-time Markov chains with affine transition rates, typically encountered in stochastic chemical kinetics. Following an optimization approach, we take advantage of existing bounds from the Foster-Lyapunov stability theory to obtain functions that enable us to estimate the region of high stationary probability, as well as provide upper bounds on moments of the chain. Our method can be used to study the stationary behavior of a given chain without resorting to stochastic simulation, in a fast and efficient manner.

## Poisson-type deviation inequalities for curved continuous-time Markov chains

Joulin, Aldéric
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
89.04071%
In this paper, we present new Poisson-type deviation inequalities for continuous-time Markov chains whose Wasserstein curvature or $\Gamma$-curvature is bounded below. Although these two curvatures are equivalent for Brownian motion on Riemannian manifolds, they are not comparable in discrete settings and yield different deviation bounds. In the case of birth--death processes, we provide some conditions on the transition rates of the associated generator for such curvatures to be bounded below and we extend the deviation inequalities established [An\'{e}, C. and Ledoux, M. On logarithmic Sobolev inequalities for continuous time random walks on graphs. Probab. Theory Related Fields 116 (2000) 573--602] for continuous-time random walks, seen as models in null curvature. Some applications of these tail estimates are given for Brownian-driven Ornstein--Uhlenbeck processes and $M/M/1$ queues.; Comment: Published at http://dx.doi.org/10.3150/07-BEJ6039 in the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm)

## Explosion, implosion, and moments of passage times for continuous-time Markov chains: a semimartingale approach

Menshikov, Mikhail; Petritis, Dimitri
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
88.78561%
We establish general theorems quantifying the notion of recurrence --- through an estimation of the moments of passage times --- for irreducible continuous-time Markov chains on countably infinite state spaces. Sharp conditions of occurrence of the phenomenon of explosion are also obtained. A new phenomenon of implosion is introduced and sharp conditions for its occurrence are proven. The general results are illustrated by treating models having a difficult behaviour even in discrete time.; Comment: 33 pages

## Continuous-Time Tracking Algorithms Involving Two-Time-Scale Markov Chains

Yin, George; Zhang, Qing; Moore, John; Liu, Y J
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
79.29669%
This work is concerned with least-mean-squares (LMS) algorithms in continuous time for tracking a time-varying parameter process. A distinctive feature is that the true parameter process is changing at a fast pace driven by a finite-state Markov chain. The states of the Markov chain are divisible into a number of groups. Within each group, the transitions take place rapidly; among different groups, the transitions are infrequent. Introducing a small parameter into the generator of the Markov chain leads to a two-time-scale formulation. The tracking objective is difficult to achieve. Nevertheless, a limit result is derived yielding algorithms for limit systems. Moreover, the rates of variation of the tracking error sequence are analyzed. Under simple conditions, it is shown that a scaled sequence of the tracking errors converges weakly to a switching diffusion. In addition, a numerical example is provided and an adaptive step-size algorithm developed.