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Metric Markov Cotype


Metric Markov cotype is a property of a metric space that controls the smoothing of functions on finite reversible Markov chains. A metric space (X,d) has metric Markov cotype p>0 with constant N if, for every positive integer n and t, every stochastic matrix A=(a_(ij)) with probability vector pi satisfying pi_ia_(ij)=pi_ja_(ji), and every x_1, ..., x_n in X, there are y_1, ..., y_n in X such that

 sum_(i)pi_id(x_i,y_i)^p+tsum_(i,j)pi_ia_(ij)d(y_i,y_j)^p<=N^psum_(i,j)pi_i(1/tsum_(s=1)^tA^s)_(ij)d(x_i,x_j)^p.

The least possible N is denoted N_p(X) (Mendel and Naor 2013). The points y_i may leave the subset containing the original x_i, which is why the property need not pass to subsets.

For p=2, this smoothing property supports Lipschitz extension problem results with Hilbert space sources.


See also

Lipschitz Extension Problem, Markov Chain, Markov Type, Metric Space, Operator Cotype, Stochastic Matrix

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References

Mendel, M. and Naor, A. "Spectral Calculus and Lipschitz Extension for Barycentric Metric Spaces." Anal. Geom. Metric Spaces 1, 163-199, 2013. https://doi.org/10.2478/agms-2013-0003.

Cite this as:

Weisstein, Eric W. "Metric Markov Cotype." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/MetricMarkovCotype.html

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