TY - JOUR

T1 - Types of markov fields and tilings

AU - Baryshnikov, Yuliy

AU - Duda, Jaroslaw Jarek

AU - Szpankowski, Wojciech

PY - 2016/8

Y1 - 2016/8

N2 - The method of types is one of the most popular techniques in information theory and combinatorics. However, thus far the method has been mostly applied to 1-D Markov processes, and it has not been thoroughly studied for general Markov fields. Markov fields over a finite alphabet of size $m\ge 2$ can be viewed as models for multidimensional systems with local interactions. The locality of these interactions is represented by a shape $\mathcal {S}$ while its marking by symbols of the underlying alphabet is called a tile. Two assignments in a Markov field have the same type if they have the same empirical distribution, i.e., if they have the same number of tiles of a given type. Our goal is to study the growth of the number of possible Markov field types in either a $d$ -dimensional box of lengths $n-{1}, \ldots , n-{d}$ or its cyclic counterpart, a $d$ -dimensional torus. We relate this question to the enumeration of nonnegative integer solutions of a large system of Diophantine linear equations called the conservation laws. We view a Markov type as a vector in a $D=m^{| {\mathcal {S}}|}$ dimensional space and count the number of such vectors satisfying the conservation laws, which turns out to be the number of integer points in a certain polytope. For the torus, this polytope is of dimension $\mu =D-1-\mathrm {rk}( {\mathrm {\mathrm{C}}})$ , where $\mathrm {rk( {\mathrm {\mathrm{C}}})}$ is the number of linearly independent conservation laws $ {\mathrm {\mathrm{C}}}$. This provides an upper bound on the number of types. Then, we construct a matching lower bound leading to the conclusion that the number of types in the torus Markov field is $\Theta (N^\mu )$ , where $N=n-{1}\ldots n-{d}$. These results are derived by geometric tools, including ideas of discrete and convex multidimensional geometry.

AB - The method of types is one of the most popular techniques in information theory and combinatorics. However, thus far the method has been mostly applied to 1-D Markov processes, and it has not been thoroughly studied for general Markov fields. Markov fields over a finite alphabet of size $m\ge 2$ can be viewed as models for multidimensional systems with local interactions. The locality of these interactions is represented by a shape $\mathcal {S}$ while its marking by symbols of the underlying alphabet is called a tile. Two assignments in a Markov field have the same type if they have the same empirical distribution, i.e., if they have the same number of tiles of a given type. Our goal is to study the growth of the number of possible Markov field types in either a $d$ -dimensional box of lengths $n-{1}, \ldots , n-{d}$ or its cyclic counterpart, a $d$ -dimensional torus. We relate this question to the enumeration of nonnegative integer solutions of a large system of Diophantine linear equations called the conservation laws. We view a Markov type as a vector in a $D=m^{| {\mathcal {S}}|}$ dimensional space and count the number of such vectors satisfying the conservation laws, which turns out to be the number of integer points in a certain polytope. For the torus, this polytope is of dimension $\mu =D-1-\mathrm {rk}( {\mathrm {\mathrm{C}}})$ , where $\mathrm {rk( {\mathrm {\mathrm{C}}})}$ is the number of linearly independent conservation laws $ {\mathrm {\mathrm{C}}}$. This provides an upper bound on the number of types. Then, we construct a matching lower bound leading to the conclusion that the number of types in the torus Markov field is $\Theta (N^\mu )$ , where $N=n-{1}\ldots n-{d}$. These results are derived by geometric tools, including ideas of discrete and convex multidimensional geometry.

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U2 - 10.1109/TIT.2016.2573834

DO - 10.1109/TIT.2016.2573834

M3 - Article

AN - SCOPUS:84978646732

VL - 62

SP - 4361

EP - 4375

JO - IRE Professional Group on Information Theory

JF - IRE Professional Group on Information Theory

SN - 0018-9448

IS - 8

M1 - 7480427

ER -