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arxiv: 1906.08384 · v1 · pith:XIX2ZEWCnew · submitted 2019-06-19 · 🧮 math.DS · q-bio.MN

Endotactic Networks and Toric Differential Inclusions

Gheorghe Craciun , Abhishek Deshpande This is my paper

Pith reviewed 2026-05-25 19:40 UTC · model grok-4.3

classification 🧮 math.DS q-bio.MN
keywords endotactic networkstoric differential inclusionspersistenceweakly reversible networksglobal attractor conjecturechemical reaction networksdynamical systems
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The pith

Endotactic dynamical systems can be embedded into toric differential inclusions, and endotactic networks form essentially the largest class with this property.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper shows that endotactic dynamical systems admit an embedding into toric differential inclusions. The embedding technique had previously been established only for the smaller class of weakly reversible networks. By extending the construction to endotactic networks, the result covers a wider set of biological interaction networks. The authors further establish that endotactic networks are essentially maximal among networks that permit such an embedding. This matters for studying persistence, the property that no species goes extinct in the model.

Core claim

We show that the larger class of endotactic dynamical systems can also be embedded into toric differential inclusions. Moreover, we show that, essentially, endotactic networks form the largest class of networks with this property.

What carries the argument

The embedding of endotactic dynamical systems into toric differential inclusions, which generalizes the prior construction limited to weakly reversible networks.

If this is right

  • Persistence analysis via toric inclusions now applies to endotactic networks in addition to weakly reversible ones.
  • The global attractor conjecture approach extends directly to the larger endotactic class.
  • Endotactic networks mark the essential boundary of networks that admit the toric embedding.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The result draws a sharp line separating networks whose dynamics can be studied through toric inclusions from those that cannot.
  • Proof strategies for non-extinction in chemical reaction networks may now target endotactic examples that fall outside the weakly reversible subclass.
  • Checking whether a given network is endotactic could serve as a practical test for whether the toric embedding is available.

Load-bearing premise

The structural definition of endotactic networks permits the toric embedding technique to generalize from weakly reversible networks without introducing obstructions that block some endotactic cases.

What would settle it

A specific endotactic network whose trajectories cannot be realized inside any toric differential inclusion would disprove the embedding claim.

Figures

Figures reproduced from arXiv: 1906.08384 by Abhishek Deshpande, Gheorghe Craciun.

Figure 1
Figure 1. Figure 1: Examples of E-graphs. An E-graph G = (V, E) is reversible if for every edge si → s ′ i ∈ E, we also have s ′ i → si ∈ E. An E-graph is weakly reversible if every edge in E is part of some cycle [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Other examples of E-graphs. Dotted black lines indicate the convex hull of the set of source vertices. Red arrows are inward pointing normals to this convex hull. (a) This E-graph is not endotactic, since its one-dimensional projection on at least one of the inward pointing red normals (in fact all of them in this case) is not endotactic. (b) This E-graph is endotactic since its one-dimensional projections… view at source ↗
Figure 3
Figure 3. Figure 3: gives examples of hyperplane-generated polyhedral fans in R 2 and R 3 . Note that in general, an entire hyperplane is not a cone in the polyhedral fan (unless the fan consists of exactly one hyperplane, in which case the cones in the fan are the hyperplane and the two-half spaces adjoining it), since its intersection with a maximal cone is not a face of the hyperplane [PITH_FULL_IMAGE:figures/full_fig_p00… view at source ↗
Figure 4
Figure 4. Figure 4: (a) Hyperplane-generated polyhedral fan. This fan contains 13 cones: six maximal cones, six cones of dimension one and one cone of dimension zero. (b) The blue cones represent the right-hand side of the toric differential inclusion corresponding to the hyperplane-generated polyhedral fan given in (a) for points X =log x away from the origin. For points near the origin that are demarcated by the red region,… view at source ↗
Figure 5
Figure 5. Figure 5: Figure illustrating σ(w) in a hyperplane-generated polyhedral fan. for some C1, C2, ..., Ck ∈ R. Then, the right-hand side of the toric differential inclusion at X is given by RHS(TFH,δ(X)) = X k i=1 Ci !o = \ k i=1 C o i . (25) Choose a one-dimensional generator Ci of P and consider the vector w ∈ Ci such that ||w|| = 1. Define σ(w) = {M ∈ R n | dist(M, C) > δ for all C ∈ FH such that w ∈/ C}. (26) Refer … view at source ↗
Figure 6
Figure 6. Figure 6: Illustration of the fact that to show dx dt [PITH_FULL_IMAGE:figures/full_fig_p016_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: E-graph depicting a basic circadian clock model. Here, Pi and Ti denote the proteins PER (period) and TIM (timeless) respectively, in various phosphorylation states. Ci denotes different forms of the PER-TIM complex [PITH_FULL_IMAGE:figures/full_fig_p019_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Example of a Thomas-type model. Here U denotes uric acid and V denotes oxygen [PITH_FULL_IMAGE:figures/full_fig_p020_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: shows an E-graph that generates the dynamics given by Equation 74. In this figure, the edge vectors for the edges labelled by the rate constants k0, k1, k2, k3, k4 are   −1 0 0   ,   1 0.3 0  ,   −1 −1 0  ,   0.3 −0.3 0.8   ,   0 0 −1   respectively [PITH_FULL_IMAGE:figures/full_fig_p020_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Endotactic E-graph that generates the dynamics corresponding to the relative concentrations for network (75). 8 Acknowledgements G.C. is supported by NSF grants DMS-1412643 and DMS-1816238. A.D. acknowledges Van Vleck Visiting Assistant Professorship from the Department of Mathematics at University of Wisconsin Madison. We thank Polly Yu for suggesting several improvements to the presentation of these res… view at source ↗
read the original abstract

An important dynamical property of biological interaction networks is persistence, which intuitively means that "no species goes extinct". It has been conjectured that dynamical system models of weakly reversible networks (i.e., networks for which each reaction is part of a cycle) are persistent. The property of persistence is also related to the well known global attractor conjecture. An approach for the proof of the global attractor conjecture uses an embedding of weakly reversible dynamical systems into toric differential inclusions. We show that the larger class of endotactic dynamical systems can also be embedded into toric differential inclusions. Moreover, we show that, essentially, endotactic networks form the largest class of networks with this property.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 2 minor

Summary. The manuscript proves that endotactic dynamical systems embed into toric differential inclusions by generalizing the construction previously used for weakly reversible networks. It further shows that endotactic networks are essentially maximal among networks admitting such an embedding. The work is motivated by persistence questions in reaction network theory and the global attractor conjecture.

Significance. If the embedding and maximality results hold, the paper meaningfully enlarges the class of networks for which toric-inclusion techniques can be applied to persistence, while clarifying the boundary of the method. The explicit maximality statement is a strength that helps delineate the reach of toric embeddings in chemical reaction network theory.

minor comments (2)
  1. The phrase 'essentially the largest class' in the abstract and introduction should be replaced by a precise statement of the maximality theorem (including any technical caveats) so that readers can assess the claim without ambiguity.
  2. Notation for the embedding map and the toric differential inclusion should be introduced with a single, self-contained definition early in the paper rather than being assembled piecemeal across sections.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the supportive summary, significance assessment, and recommendation of minor revision. No specific major comments were provided in the report.

Circularity Check

0 steps flagged

No circularity: self-contained generalization of toric embedding

full rationale

The paper's central result is a mathematical embedding of endotactic dynamical systems into toric differential inclusions, generalizing a prior construction for weakly reversible networks, together with a maximality statement. No step reduces by definition to its own inputs, no fitted parameter is relabeled as a prediction, and no load-bearing premise rests on a self-citation chain whose verification is internal to the present work. The structural definitions and embedding construction are presented as independent of the target claim, making the derivation self-contained against external mathematical benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Based on abstract only; the result rests on standard definitions of weakly reversible and endotactic networks plus properties of toric differential inclusions from prior work. No free parameters or invented entities are mentioned.

axioms (1)
  • standard math Dynamical systems generated by reaction networks satisfy standard existence and uniqueness properties for solutions.
    Implicit in any embedding of such systems into differential inclusions.

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