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Markov additive process

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This article is about bivariate processes. For arrival processes to queues, see Markovian arrival process.

In applied probability, a Markov additive process (MAP) is a bivariate Markov process where the future states depends only on one of the variables.[1]

Definition

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Finite or countable state space for J(t)

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The process { ( X ( t ) , J ( t ) ) : t 0 } {\displaystyle \{(X(t),J(t)):t\geq 0\}} {\displaystyle \{(X(t),J(t)):t\geq 0\}} is a Markov additive process with continuous time parameter t if[1]

  1. { ( X ( t ) , J ( t ) ) ; t 0 } {\displaystyle \{(X(t),J(t));t\geq 0\}} {\displaystyle \{(X(t),J(t));t\geq 0\}} is a Markov process
  2. the conditional distribution of ( X ( t + s ) X ( t ) , J ( t + s ) ) {\displaystyle (X(t+s)-X(t),J(t+s))} {\displaystyle (X(t+s)-X(t),J(t+s))} given ( X ( t ) , J ( t ) ) {\displaystyle (X(t),J(t))} {\displaystyle (X(t),J(t))} depends only on J ( t ) {\displaystyle J(t)} {\displaystyle J(t)}.

The state space of the process is R×ばつ S where X(t) takes real values and J(t) takes values in some countable set S.

General state space for J(t)

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For the case where J(t) takes a more general state space the evolution of X(t) is governed by J(t) in the sense that for any f and g we require[2]

E [ f ( X t + s X t ) g ( J t + s ) | F t ] = E J t , 0 [ f ( X s ) g ( J s ) ] {\displaystyle \mathbb {E} [f(X_{t+s}-X_{t})g(J_{t+s})|{\mathcal {F}}_{t}]=\mathbb {E} _{J_{t},0}[f(X_{s})g(J_{s})]} {\displaystyle \mathbb {E} [f(X_{t+s}-X_{t})g(J_{t+s})|{\mathcal {F}}_{t}]=\mathbb {E} _{J_{t},0}[f(X_{s})g(J_{s})]}.

Example

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A fluid queue is a Markov additive process where J(t) is a continuous-time Markov chain [clarification needed ][example needed ].

Applications

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Çinlar uses the unique structure of the MAP to prove that, given a gamma process with a shape parameter that is a function of Brownian motion, the resulting lifetime is distributed according to the Weibull distribution.

Kharoufeh presents a compact transform expression for the failure distribution for wear processes of a component degrading according to a Markovian environment inducing state-dependent continuous linear wear by using the properties of a MAP and assuming the wear process to be temporally homogeneous and that the environmental process has a finite state space.

Notes

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  1. ^ a b Magiera, R. (1998). "Optimal Sequential Estimation for Markov-Additive Processes". Advances in Stochastic Models for Reliability, Quality and Safety. pp. 167–181. doi:10.1007/978-1-4612-2234-7_12. ISBN 978-1-4612-7466-7.
  2. ^ Asmussen, S. R. (2003). "Markov Additive Models". Applied Probability and Queues. Stochastic Modelling and Applied Probability. Vol. 51. pp. 302–339. doi:10.1007/0-387-21525-5_11. ISBN 978-0-387-00211-8.
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