Abstract:
A theorem is proved that makes it possible to take into account the “hard-core”
potential of contours and reduce the study of the convergence of the Mayer
expansions of the gas of contours to the remaining part of the interaction.
In particular, for a model with nearest-neighbor interaction, in which
$$
U(\alpha)=\sum_{|x-y|=1}\varepsilon(\alpha(x)\alpha^{-1}(y)),
$$ $\alpha(x)$ takes values in the discrete group $G$ with identity $e$, $\varepsilon(\alpha)=\varepsilon(\alpha^{-1})$$\forall\alpha\ne e$,
$\varepsilon(e)=0$ and
$$
\sum_{\alpha\in G\setminus e}\exp\{-\beta U(\alpha)\}
\underset{\beta\to\infty}\longrightarrow0,
$$
the existence is proved of not less than $|G|$ ($|G|\leqslant\infty$) limit Gibbs distributions, which are small perturbations of the ground states $\alpha(x)=\alpha_0\in G$.