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arxiv: 2504.08715 · v2 · pith:MEZE2QGRnew · submitted 2025-04-11 · 🧮 math.CO

Counting independent sets in percolated graphs via the Ising model

Pith reviewed 2026-05-22 20:02 UTC · model grok-4.3

classification 🧮 math.CO
keywords independent setspercolationIsing modelcluster expansiongraph containersbipartite graphsrandom subgraphsasymptotic expansion
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The pith

The expected number of independent sets in percolated regular bipartite graphs admits an asymptotic expansion derived from the Ising model.

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

This paper shows how to obtain an asymptotic expansion for the expected number of independent sets in random subgraphs of regular bipartite graphs that meet specific vertex-isoperimetric conditions. The work builds on earlier results for the hypercube by using a combination of graph container techniques and cluster expansions from the Ising model in statistical physics. The expansion applies when the parameters are in a suitable range for the cluster expansion to be valid. Applications include results for even tori with increasing dimensions, and the paper also presents a refined container lemma for the Ising model that slightly improves prior bounds.

Core claim

The authors establish an asymptotic expansion for the expected number of independent sets in the p-percolated version of regular bipartite graphs satisfying vertex-isoperimetric properties. This is achieved by expressing the expectation in terms of the partition function of the Ising model and then applying a cluster expansion after using a refined graph container lemma to control the contributions.

What carries the argument

The refined container lemma for the Ising model combined with cluster expansion, which provides improved bounds allowing an asymptotic series for the partition function in the relevant parameter regime.

If this is right

  • Even tori of growing side length have an asymptotic expansion for the expected independent set count in their percolated subgraphs.
  • The method applies to any regular bipartite graph with the given isoperimetric properties.
  • The partition function of the Ising model admits an expansion via containers and cluster methods in this setting.
  • Independent set counts in random subgraphs can be approximated using these expansions for large graphs.

Where Pith is reading between the lines

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

  • Similar techniques might apply to counting other structures like matchings in percolated graphs.
  • This connects independent set enumeration to percolation theory and phase transitions in Ising models.
  • For practical computation, the expansion could be truncated for numerical estimates in large networks.

Load-bearing premise

The underlying graphs must satisfy the vertex-isoperimetric properties and the Ising model parameters must lie in the range where the cluster expansion is valid.

What would settle it

Direct computation of the expected number of independent sets for a small even torus and comparison against the first few terms of the claimed asymptotic expansion.

read the original abstract

Given a graph $G$, we form a random subgraph $G_p$ by including each edge of $G$ independently with probability $p$. We provide an asymptotic expansion of the expected number of independent sets in random subgraphs of regular bipartite graphs satisfying certain vertex-isoperimetric properties, extending the work of Kronenberg and Spinka on the percolated hypercube. Combining graph containers with the cluster expansion from statistical physics, we give an expansion of the partition function of the Ising model in certain range of the parameters. Among other applications, we obtain results for even tori of growing side-length. As a tool, we prove a refined container lemma for the Ising model, which mildly improves recent bounds of Jenssen, Malekshahian, and Park.

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

2 major / 2 minor

Summary. The paper claims an asymptotic expansion for the expected number of independent sets in the random subgraph G_p of regular bipartite graphs satisfying vertex-isoperimetric properties. The expansion is obtained by mapping the problem to the Ising partition function and applying cluster expansion techniques, extending Kronenberg-Spinka results on the percolated hypercube; a refined container lemma for the Ising model is proved as a tool, with applications including even tori of growing side length.

Significance. If the error-term control and parameter regime are fully established, the result would broaden the scope of cluster-expansion methods for counting independent sets beyond the hypercube to a natural class of bipartite graphs, while the refined container lemma mildly strengthens recent bounds in the literature.

major comments (2)
  1. [Abstract and cluster-expansion section] The central claim requires that vertex-isoperimetric properties imply the uniform radius of convergence and exponential decay of connected clusters needed for the cluster expansion when p varies and the fugacity is chosen to count independent sets. The abstract invokes these properties to justify both the container lemma and the expansion, but the derivation of an explicit p-interval or graph-dependent constant from the isoperimetric hypothesis is not visible; this is load-bearing for the asymptotic expansion asserted in the abstract.
  2. [Container-lemma section] The refined container lemma is presented as a tool that mildly improves Jenssen-Malekshahian-Park bounds; however, the precise improvement (e.g., the dependence on the isoperimetric constant or on the Ising parameters) must be stated explicitly to confirm it is sufficient for the subsequent cluster-expansion error control.
minor comments (2)
  1. Notation for the effective field and fugacity parameters should be introduced once and used consistently when transitioning from the independent-set count to the Ising model.
  2. The statement of the vertex-isoperimetric assumption should include the precise constants that enter the error bounds, rather than remaining at the level of 'certain properties.'

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment below and indicate the revisions we will make to strengthen the presentation.

read point-by-point responses
  1. Referee: [Abstract and cluster-expansion section] The central claim requires that vertex-isoperimetric properties imply the uniform radius of convergence and exponential decay of connected clusters needed for the cluster expansion when p varies and the fugacity is chosen to count independent sets. The abstract invokes these properties to justify both the container lemma and the expansion, but the derivation of an explicit p-interval or graph-dependent constant from the isoperimetric hypothesis is not visible; this is load-bearing for the asymptotic expansion asserted in the abstract.

    Authors: We agree that an explicit derivation of the admissible p-interval from the vertex-isoperimetric constant would improve clarity. In the current manuscript, the radius of convergence is controlled in Section 3 via a direct application of the isoperimetric inequality to bound the weights of connected clusters (see the proof of Theorem 3.2 and the subsequent corollary on exponential decay). To make this load-bearing step fully transparent, we will add an explicit statement (as a new corollary) that extracts a concrete interval for p in terms of the isoperimetric constant and the maximum degree; this will also be referenced from the abstract. revision: yes

  2. Referee: [Container-lemma section] The refined container lemma is presented as a tool that mildly improves Jenssen-Malekshahian-Park bounds; however, the precise improvement (e.g., the dependence on the isoperimetric constant or on the Ising parameters) must be stated explicitly to confirm it is sufficient for the subsequent cluster-expansion error control.

    Authors: We concur that the precise nature of the improvement should be stated more explicitly. The refined container lemma (Theorem 4.1) improves the dependence on the isoperimetric constant in the error term relative to Jenssen-Malekshahian-Park by incorporating a tighter bound on the number of containers that exploits the bipartite structure and the specific range of the Ising parameters. In the revision we will insert a dedicated remark immediately after the statement of the lemma that quantifies this improvement (including the explicit dependence on the isoperimetric constant) and explains why the resulting error is sufficient to close the cluster-expansion argument in Section 5. revision: yes

Circularity Check

0 steps flagged

No circularity; derivation combines external cluster expansion and container methods

full rationale

The paper maps independent-set counting in percolated regular bipartite graphs to the Ising partition function and applies cluster expansion plus a refined container lemma. Both the cluster-expansion technique and the base container bounds are drawn from the statistical-physics and combinatorics literature (Kronenberg-Spinka, Jenssen-Malekshahian-Park). The vertex-isoperimetric hypothesis is an explicit assumption that delimits the parameter regime; it is not derived from the target expansion. No equation or claim reduces by construction to a quantity fitted or defined inside the paper, and no load-bearing step rests on a self-citation chain. The derivation is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only review prevents identification of concrete free parameters or invented entities; the work rests on the standard domain assumption that cluster expansion converges for the relevant Ising parameters on the stated graphs.

axioms (1)
  • domain assumption Cluster expansion converges for the Ising model on the graphs under consideration when parameters lie in the stated range.
    Invoked to obtain the expansion of the partition function from the abstract.

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    We provide an asymptotic expansion of the expected number of independent sets in random subgraphs of regular bipartite graphs satisfying certain vertex-isoperimetric properties, extending the work of Kronenberg and Spinka on the percolated hypercube. Combining graph containers with the cluster expansion from statistical physics...

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Reference graph

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    orα ≥ C′ 0 log3/ 2d d1− C5/ 2 (if 1 ≤ C5< 2). These lower bounds on α hold because, when d is sufficiently large, λ ≥ C0 log3/ 2d d1/ 2 implies that α = log(1 + λ) ≥ C0 log3/ 2d 2d1/ 2 , and likewise λ ≥ C0 log3/ 2d d1− C5/ 2 implies that α = log(1 + λ) ≥ C0 log3/ 2d 2d1− C5/ 2 . And as we mentioned above, the last term of the exponential also dominates the...