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**A measure concentration inequality for contracting Markov chains.**
*(English)*
Zbl 0856.60072

Summary: The concentration of measure phenomenon in product spaces means the following: if a subset \(A\) of the \(n\)th power of a probability space \(\mathcal X\) does not have too small a probability, then very large probability is concentrated in a small neighborhood of \(A\). The neighborhood is in many cases understood in the sense of Hamming distance, and then measure concentration is known to occur for product probability measures, and also for the distribution of some processes with very fast and uniform decay of memory. Recently, Talagrand introduced another notion of neighborhood of sets for which he proved a similar measure concentration inequality which in many cases allows more efficient applications than the one for a Hamming neighborhood. So far this inequality has only been proved for product distributions. The aim of this paper is to give a new proof of Talagrand’s inequality, which admits an extension to contracting Markov chains. The proof is based on a new asymmetric notion of distance between probability measures, and bounding this distance by informational divergence. As an application, we analyze the bin packing problem for Markov chains.

### MSC:

60J10 | Markov chains (discrete-time Markov processes on discrete state spaces) |

60E15 | Inequalities; stochastic orderings |

### Keywords:

concentration of measure phenomenon in product spaces; Hamming distance; Talagrand’s inequality; contracting Markov chains; packing problem### References:

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