## Electronic Journal of Probability

### Occupation laws for some time-nonhomogeneous Markov chains

#### Abstract

We consider finite-state time-nonhomogeneous Markov chains whose transition matrix at time $n$ is $I+G/n^z$ where $G$ is a generator'' matrix, that is $G(i,j)>0$ for $i,j$ distinct, and $G(i,i)= -\sum_{k\ne i} G(i,k)$, and $z>0$ is a strength parameter. In these chains, as time grows, the positions are less and less likely to change, and so form simple models of age-dependent time-reinforcing schemes. These chains, however, exhibit a trichotomy of occupation behaviors depending on parameters.

We show that the average occupation or empirical distribution vector up to time $n$, when variously $0< z< 1$, $z>1$ or $z=1$, converges in probability to a unique stationary'' vector $n_G$, converges in law to a nontrivial mixture of point measures, or converges in law to a distribution $m_G$ with no atoms and full support on a simplex respectively, as $n$ tends to infinity. This last type of limit can be interpreted as a sort of spreading'' between the cases $0< z < 1$ and $z>1$.

In particular, when $G$ is appropriately chosen, $m_G$ is a Dirichlet distribution, reminiscent of results in Polya urns.

#### Article information

Source
Electron. J. Probab., Volume 12 (2007), paper no. 23, 661-683.

Dates
Accepted: 16 May 2007
First available in Project Euclid: 1 June 2016

Permanent link to this document
https://projecteuclid.org/euclid.ejp/1464818494

Digital Object Identifier
doi:10.1214/EJP.v12-413

Mathematical Reviews number (MathSciNet)
MR2318406

Zentralblatt MATH identifier
1127.60068

Subjects
Primary: 60J10: Markov chains (discrete-time Markov processes on discrete state spaces)
Secondary: 60F10: Large deviations

Rights

#### Citation

Dietz, Zach; Sethuraman, Sunder. Occupation laws for some time-nonhomogeneous Markov chains. Electron. J. Probab. 12 (2007), paper no. 23, 661--683. doi:10.1214/EJP.v12-413. https://projecteuclid.org/euclid.ejp/1464818494

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