English

From Copying to Corelations via Ancestry Partitions

Category Theory 2026-04-28 v2 Logic in Computer Science

Abstract

We study the free PROP Syn(δ)\mathrm{Syn}(\delta) on a single binary generator δ:12\delta:1\to 2. The ancestry functor Π:Syn(δ)FinCorel\Pi:\mathrm{Syn}(\delta)\to \mathrm{FinCorel}, defined by connected components of the underlying undirected string diagram, has image the sub-PROP FinCorel\mathrm{FinCorel}^{\circ} of finite corelations whose equivalence classes contain exactly one input and at least one output. The induced quotient [ \mathrm{AncQ}:=\mathrm{Syn}(\delta)/\ker(\Pi) ] is equivalent as a PROP to Cocom\mathrm{Cocom}, the PROP for non-counital cocommutative comonoids. We then locate this primitive construction inside the standard cospan/corelation framework: Cospan(B)\mathrm{Cospan}(\mathcal B) realizes pushout-style gluing as a free hypergraph category; Cospan(FinSet)\mathrm{Cospan}(\mathrm{FinSet}) collapses under jointly epic corestriction to FinCorel\mathrm{FinCorel}, the PROP for extraspecial commutative Frobenius monoids; and the Yoneda envelope [ \mathcal W=\mathrm{Fun}(\mathrm{FinCorel}^{op},\mathrm{Spc}) ] is a presheaf \infty-topos carrying the standard subobject, modality, and monotone fixed-point apparatus. The PROP-level identification AncQCocom\mathrm{AncQ}\simeq \mathrm{Cocom} is the only result claimed as new; the remaining material is organizational and reduces explicitly to cited classical results.

Keywords

Cite

@article{arxiv.2505.22931,
  title  = {From Copying to Corelations via Ancestry Partitions},
  author = {Andreu Ballus Santacana},
  journal= {arXiv preprint arXiv:2505.22931},
  year   = {2026}
}

Comments

Substantially revised version. The previous version used a different categorical setup. The present version supersedes it for formal purposes and claims only the PROP-level identification $\mathrm{AncQ}\simeq \mathrm{Cocom}$ as new; the remaining material is organizational and reduced to cited classical results. 19 pages