English

Hyper-Operations and Extension of Scalars from $\mathbb{F}_1$ to $\mathbb{Z}$

Algebraic Geometry 2026-04-28 v1 Category Theory Rings and Algebras

Abstract

The additive structure of F1\mathbb{F}_1-modules (in the sense of Segal's Γ\Gamma-sets) differs fundamentally from that of abelian groups: addition is encoded through a family of nn-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 nn-ary sums are controlled by successive binary operations. This enables us to construct an extension of scalars functor F1Z:F1ModAb-\otimes_{\mathbb{F}_1} \mathbb{Z}: \mathbb{F}_1\mathbf{Mod} \to \mathbf{Ab} that universally strictifies the hyper-additive structure of F1\mathbb{F}_1-modules into classical abelian group addition. We prove this functor is left adjoint to the Eilenberg-MacLane functor H:AbF1ModH: \mathbf{Ab} \to \mathbb{F}_1\mathbf{Mod}. Extending to the multiplicative setting, we obtain an adjunction F1Z:F1AlgCRing:H-\otimes_{\mathbb{F}_1} \mathbb{Z}: \mathbb{F}_1\mathbf{Alg} \leftrightarrows \mathbf{CRing} : H between commutative F1\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.

Keywords

Cite

@article{arxiv.2604.24568,
  title  = {Hyper-Operations and Extension of Scalars from $\mathbb{F}_1$ to $\mathbb{Z}$},
  author = {Luqiao Xu},
  journal= {arXiv preprint arXiv:2604.24568},
  year   = {2026}
}

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28 pages