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arXiv · 2604.18588

A new limit variety of additively idempotent semirings

Simin Lyu·Miaomiao Ren·Mengya Yue
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Abstract

We establish a sufficient condition for an additively idempotent semiring to be nonfinitely based. Applying this condition, we prove that the six-element additively idempotent semiring $SR_6$ has no finite basis for its identity. Furthermore, we provide a complete description of the subvariety lattice of the variety $\mathsf{V}(SR_6)$ generated by $SR_6$, showing that it forms a four-element chain. Our results demonstrate that $\mathsf{V}(SR_6)$ is a limit variety: it is itself nonfinitely based, yet all of its proper subvarieties are finitely based. Moreover, $SR_6$ is the smallest known example of an additively idempotent semiring generating a limit variety.

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Simin Lyu, Miaomiao Ren, Mengya Yue. 2026-03-14. A new limit variety of additively idempotent semirings. https://arxiv.org/abs/2604.18588

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