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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2604.24568 |
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| _version_ | 1866913065635676160 |
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| author | Xu, Luqiao |
| author_facet | Xu, Luqiao |
| contents | The additive structure of $\mathbb{F}_1$-modules (in the sense of Segal's $Γ$-sets) differs fundamentally from that of abelian groups: addition is encoded through a family of $n$-ary hyper-operations that are multivalued and do not satisfy classical associativity. We establish a \emph{law of generalized associativity} showing that, despite this failure of strict associativity, all $n$-ary sums are controlled by successive binary operations. This enables us to construct an extension of scalars functor $-\otimes_{\mathbb{F}_1} \mathbb{Z}: \mathbb{F}_1\mathbf{Mod} \to \mathbf{Ab}$ that universally strictifies the hyper-additive structure of $\mathbb{F}_1$-modules into classical abelian group addition. We prove this functor is left adjoint to the Eilenberg-MacLane functor $H: \mathbf{Ab} \to \mathbb{F}_1\mathbf{Mod}$. Extending to the multiplicative setting, we obtain an adjunction $-\otimes_{\mathbb{F}_1} \mathbb{Z}: \mathbb{F}_1\mathbf{Alg} \leftrightarrows \mathbf{CRing} : H$ between commutative $\mathbb{F}_1$-algebras and commutative rings. This recovers Deitmar's monoid ring construction for spherical monoid algebras and provides a base change mechanism needed for absolute algebraic geometry. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_24568 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Hyper-Operations and Extension of Scalars from $\mathbb{F}_1$ to $\mathbb{Z}$ Xu, Luqiao Algebraic Geometry Category Theory Rings and Algebras 20N20, 14A20, 14G40 The additive structure of $\mathbb{F}_1$-modules (in the sense of Segal's $Γ$-sets) differs fundamentally from that of abelian groups: addition is encoded through a family of $n$-ary hyper-operations that are multivalued and do not satisfy classical associativity. We establish a \emph{law of generalized associativity} showing that, despite this failure of strict associativity, all $n$-ary sums are controlled by successive binary operations. This enables us to construct an extension of scalars functor $-\otimes_{\mathbb{F}_1} \mathbb{Z}: \mathbb{F}_1\mathbf{Mod} \to \mathbf{Ab}$ that universally strictifies the hyper-additive structure of $\mathbb{F}_1$-modules into classical abelian group addition. We prove this functor is left adjoint to the Eilenberg-MacLane functor $H: \mathbf{Ab} \to \mathbb{F}_1\mathbf{Mod}$. Extending to the multiplicative setting, we obtain an adjunction $-\otimes_{\mathbb{F}_1} \mathbb{Z}: \mathbb{F}_1\mathbf{Alg} \leftrightarrows \mathbf{CRing} : H$ between commutative $\mathbb{F}_1$-algebras and commutative rings. This recovers Deitmar's monoid ring construction for spherical monoid algebras and provides a base change mechanism needed for absolute algebraic geometry. |
| title | Hyper-Operations and Extension of Scalars from $\mathbb{F}_1$ to $\mathbb{Z}$ |
| topic | Algebraic Geometry Category Theory Rings and Algebras 20N20, 14A20, 14G40 |
| url | https://arxiv.org/abs/2604.24568 |