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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2509.23818 |
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| _version_ | 1866918149929041920 |
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| author | Rago, Balint |
| author_facet | Rago, Balint |
| contents | Let $H$ be a (multiplicatively written) monoid. The family $\mathcal{P}_{\text{fin},1}(H)$ of finite subsets of $H$ containing the identity element is itself a monoid when endowed with setwise multiplication induced by $H$. Tringali and Yan proved that two monoids $H_1$ and $H_2$ contained in a special class of commutative, cancellative monoids are isomorphic if and only if $\mathcal{P}_{\text{fin},1}(H_1)$ and $\mathcal{P}_{\text{fin},1}(H_2)$ are. Moreover, they raised the question whether the same holds in the general setting of cancellative monoids. We show that if $H_1$ and $H_2$ are (commutative) valuation monoids with trivial unit groups and isomorphic quotient groups, then $\mathcal{P}_{\text{fin},1}(H_1)\simeq\mathcal{P}_{\text{fin},1}(H_2)$. This provides a negative answer to Tringali and Yans question already within the class of valuation submonoids of the additive group $\mathbb{Z}^2$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_23818 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A counterexample to an isomorphism problem for power monoids Rago, Balint Commutative Algebra Combinatorics 20M14 Let $H$ be a (multiplicatively written) monoid. The family $\mathcal{P}_{\text{fin},1}(H)$ of finite subsets of $H$ containing the identity element is itself a monoid when endowed with setwise multiplication induced by $H$. Tringali and Yan proved that two monoids $H_1$ and $H_2$ contained in a special class of commutative, cancellative monoids are isomorphic if and only if $\mathcal{P}_{\text{fin},1}(H_1)$ and $\mathcal{P}_{\text{fin},1}(H_2)$ are. Moreover, they raised the question whether the same holds in the general setting of cancellative monoids. We show that if $H_1$ and $H_2$ are (commutative) valuation monoids with trivial unit groups and isomorphic quotient groups, then $\mathcal{P}_{\text{fin},1}(H_1)\simeq\mathcal{P}_{\text{fin},1}(H_2)$. This provides a negative answer to Tringali and Yans question already within the class of valuation submonoids of the additive group $\mathbb{Z}^2$. |
| title | A counterexample to an isomorphism problem for power monoids |
| topic | Commutative Algebra Combinatorics 20M14 |
| url | https://arxiv.org/abs/2509.23818 |