Separated presentation adjunction for causal and triangular Frobenius presentations

From papers

Let Caus\mathbf{Caus} be the category of finite acyclic directed graphs equipped with a chosen topological order, with order-preserving graph homomorphisms or refinements as morphisms. Let TangFrobtri\mathbf{TangFrob}_{\mathrm{tri}} be the category of Frobenius Markov objects with tangent intervention fields v1,,vdv_1,\dots,v_d and a filtration

0=g0g1gd,gi=span{v1,,vi},0=\mathfrak g_0\subset \mathfrak g_1\subset\cdots\subset\mathfrak g_d, \qquad \mathfrak g_i=\operatorname{span}\{v_1,\dots,v_i\},

satisfying [vi,vj]g>max(i,j)[v_i,v_j]\in\mathfrak g_{>\max(i,j)}, where g>m\mathfrak g_{>m} is the span of intervention directions strictly later than mm. Let F:CausTangFrobtriF:\mathbf{Caus}\to\mathbf{TangFrob}_{\mathrm{tri}} be the geometric-realization functor, and let TangFrobsepTangFrobtri\mathbf{TangFrob}_{\mathrm{sep}}\subseteq\mathbf{TangFrob}_{\mathrm{tri}} be the separated subcategory defined by the γ\gamma-separated visible-stratum hypothesis, strengthened so that the triangular filtration and nonzero residuals are invariant under Frobenius-compatible changes of presentation. Separated presentation adjunction. On TangFrobsep\mathbf{TangFrob}_{\mathrm{sep}}, graphical extraction is functorial and the realization functor admits a right adjoint

F:CausTangFrobsep:G.F:\mathbf{Caus}\rightleftarrows\mathbf{TangFrob}_{\mathrm{sep}}:G.

Moreover, the unit η:IdCausGF\eta:\mathrm{Id}_{\mathbf{Caus}}\Rightarrow GF is an isomorphism, while the counit ϵ:FGIdTangFrobsep\epsilon:FG\Rightarrow\mathrm{Id}_{\mathbf{TangFrob}_{\mathrm{sep}}} is the triangularization map comparing each separated tangent Frobenius object with the object generated by its extracted acyclic presentation. The conjecture formalizes when tangent Frobenius data determine an ordered graphical presentation: separation should make extraction functorial, and realization followed by extraction should recover the original presentation. The source does not provide a resolution, so the status remains open; the precise strengthened separation condition and the behavior of the counit require verification.

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Primary source

Sridhar Mahadevan, “Infinitesimal Causality”, arXiv:2606.24621 (2026).

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