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arXiv · 2609.04610

A note on Ursell functions for the Blume-Capel model

Sheng Chun Yu
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Abstract

We study the sign structure of Ursell functions in the Blume--Capel model. For $\Delta \le \log 2$, we give a short proof of the alternating sign property using an Ising representation. We then construct counterexamples for every $\Delta > \log 2$, showing that the condition $\Delta \le \log 2$ is sharp.

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Sheng Chun Yu. 2026-09-04. A note on Ursell functions for the Blume-Capel model. https://arxiv.org/abs/2609.04610

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