The core decomposition equality for polygonal presentations of compacta on surfaces

Let KK be a compactum in a closed surface S\mathcal{S}, let PC\mathcal{P}\subset\mathbb{C} be a polygon whose side identifications produce a quotient topologically equivalent to S\mathcal{S}, and let τ:PS\tau:\mathcal{P}\to\mathcal{S} be the quotient projection. Put L=τ1(K)L=\tau^{-1}(K). Let DKPC\mathcal{D}_K^{PC} and DLPC\mathcal{D}_L^{PC} be the core decompositions of KK and LL, respectively, and let DKτ\mathcal{D}_K^\tau be the finest upper semicontinuous decomposition of KK into subcontinua that split none of the images τ(δ)\tau(\delta), for δDLPC\delta\in\mathcal{D}_L^{PC}.

Core decomposition equality. The core decomposition of KK satisfies

DKPC=DKτ.\mathcal{D}_K^{PC}=\mathcal{D}_K^\tau.

This identifies the core decomposition on the surface with the finest decomposition compatible with the images of the polygonal core decomposition. The supplied text gives no resolution status beyond stating the equality in a conjecture environment.

Sources & referencesView supporting material

Primary source

Jun Luo, Joerg Thuswaldner, Xiao-Ting Yao and Shuqin Zhang, “Atoms of Compacta on Closed Surfaces”, arXiv:2603.27054 (2026).

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