# What does it mean for a Markov chain to be ergodic?

## What does it mean for a Markov chain to be ergodic?

A Markov chain is said to be ergodic if there exists a positive integer such that for all pairs of states in the Markov chain, if it is started at time 0 in state then for all , the probability of being in state at time is greater than .

## How do you prove Markov chain is ergodic?

Defn: A Markov chain with finite state space is regular if some power of its transition matrix has only positive entries. P(going from x to y in n steps) > 0, so a regular chain is ergodic. To see that regular chains are a strict subclass of the ergodic chains, consider a walker going between two shops: 1 ⇆ 2.

Can a periodic Markov chain be ergodic?

The Markov chain cannot be ergodic because the long-term probability of being on a given state depends on the initial state.

### Are ergodic Markov chains irreducible?

Ergodic Markov chains are also called irreducible. A Markov chain is called a regular chain if some power of the transition matrix has only positive elements.

### What is an ergodic system?

ergodic theory [ər′gäd·ik ′thē·ə·rē] (mathematics) The study of measure-preserving transformations. (statistical mechanics) Mathematical theory which attempts to show that the various possible microscopic states of a system are equally probable, and that the system is therefore ergodic.

Is stationary process ergodic?

For a strict-sense stationary process, this means that its joint probability distribution is constant; for a wide-sense stationary process, this means that its 1st and 2nd moments are constant. An ergodic process is one where its statistical properties, like variance, can be deduced from a sufficiently long sample.

#### What’s the meaning of ergodic?

Definition of ergodic 1 : of or relating to a process in which every sequence or sizable sample is equally representative of the whole (as in regard to a statistical parameter) 2 : involving or relating to the probability that any state will recur especially : having zero probability that any state will never recur.

#### How do you know if a process is ergodic?

In physics, statistics, econometrics and signal processing, a stochastic process is said to be in an ergodic regime if an observable’s ensemble average equals the time average. In this regime, any collection of random samples from a process must represent the average statistical properties of the entire regime.

What is an ergodic function?

In mathematics, ergodicity expresses the idea that a point of a moving system, either a dynamical system or a stochastic process, will eventually visit all parts of the space that the system moves in, in a uniform and random sense.

## Does ergodic imply stationary?

Yes, ergodicity implies stationarity. Consider an ensemble of realizations generated by a random process. Ergodicity states that the time-average is equal to the ensemble average. The time-average is obtained by taking the average of a single realization, giving you a particular number.

## Is ergodic process always stationary?

Asking in relation to Friston’s Free Energy framework that assumes living systems are ergodic, but a question has been raised that ergodic processes are necessarily stationary, and living systems are not stationary, so they cannot be ergodic.

How to transform a process into a Markov chain?

Markov Process • For a Markov process{X(t), t T, S}, with state space S, its future probabilistic development is deppy ,endent only on the current state, how the process arrives at the current state is irrelevant. • Mathematically – The conditional probability of any future state given an arbitrary sequence of past states and the present

### How to create Markov chain?

– Regime 1: An autoregressive model with a low mean and low volatility – Regime 2: An autoregressive model with a low mean and high volatility – Regime 3: An autoregressive model with a high mean and low volatility – Regime 4: An autoregressive model with a high mean and high volatility

### What are the properties of a Markov chain?

Random variables and random processes. Before introducing Markov chains,let’s start with a quick reminder of some basic but important notions of probability theory.

• Markov property and Markov chain.
• Characterising the random dynamic of a Markov chain.
• How does a Markov chain work?

A state i i i has period k ≥ 1 k\\ge 1 k ≥ 1 if any chain starting at and returning to state i i i with positive

• A Markov chain is known as irreducible if there exists a chain of steps between any two states that has positive probability.
• An absorbing state i i i is a state for which P i,i = 1 P_{i,i} = 1 P i,i ​ = 1.