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Nonprobability Gibbs measures for the HC model with a countable set of spin values for a “wand”-type graph on a Cayley tree
R. M. Khakimovab,
M. T. Makhammadalievb a Romanovskii Institute of Mathematics, UzAS, Tashkent,
Uzbekistan
b Namangam State University, Namangan, Uzbekistan
Abstract:
We study Gibbs measures for the HC model with a countable set
$\mathbb Z$ of spin values and a countable set of parameters (i.e., with the activity function
$\lambda_i>0$,
$i\in \mathbb Z$) in the case of a “wand”-type graph. In this case, analyzing a functional equation that ensures the consistency condition for finite-dimensional Gibbs measures, we obtain the following results. Exact values of the parameter
$\lambda_{\mathrm{cr}}$ are determined; it is shown that for
$0<\lambda\leq\lambda_{\mathrm{cr}}$, there exists exactly one translation-invariant nonprobabilistic Gibbs measure, and for
$\lambda>\lambda_{\mathrm{cr}}$, there exist precisely three such measures on a Cayley tree of order
$2$,
$3$, or
$4$. We obtain the uniqueness conditions for
$2$-periodic nonprobabilistic Gibbs measures on a Cayley tree of an arbitrary order, as well as exact values of the parameter
$\lambda_{\mathrm{cr}}$; we also show that for
$\lambda\geq\lambda_{\mathrm{cr}}$, there exists precisely one such a measure, and for
$0<\lambda<\lambda_{\mathrm{cr}}$, there exist precisely three such measures on a Cayley tree of order
$2$ or
$3$.
Keywords:
HC model, configuration, Cayley tree, Gibbs measure, nonprobabilistic Gibbs measure, boundary law. Received: 15.04.2022
Revised: 04.06.2022
DOI:
10.4213/tmf10302