Domination above r-independence: does sparseness help?
Pith reviewed 2026-05-25 18:44 UTC · model grok-4.3
The pith
A maximal 3-independent set makes the dominating set problem FPT on nowhere dense graphs when parametrized by uncovered vertices.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
When a maximal 3-independent set X is supplied, dominating set parametrized by the size of the residual set R equals V(G) minus N[X] is W[2]-hard on general graphs, fixed-parameter tractable on nowhere dense graphs, and admits a linear kernel on bounded expansion graphs.
What carries the argument
The residual set R equals V(G) minus the closed neighborhood of a given maximal r-independent set X, which serves as the above-guarantee parameter measuring vertices not covered by the lower-bound witness.
If this is right
- For r equals 3 the problem admits algorithms whose runtime depends only on the residual size on nowhere dense graphs.
- Linear kernels exist for the r equals 3 case on bounded expansion graphs.
- For r equals 2 no FPT algorithm exists on bounded-degree or apex graphs unless P equals NP.
- For r at least 4 the above-guarantee parameter offers no additional power beyond the ordinary dominating-set parameter.
Where Pith is reading between the lines
- The value of r appears to control how much the independent-set witness separates the lower bound from the actual solution size, interacting differently with sparsity.
- Similar residual parameters might be tested on other domination-like problems restricted to sparse graph classes.
- The separation between r equals 2 and r equals 3 suggests that small changes in the independence distance can shift a problem from intractable to tractable under sparsity assumptions.
Load-bearing premise
The input set X must be a maximal r-independent set that actually lower-bounds every dominating set of the graph.
What would settle it
An FPT algorithm for the r equals 3 case running in f of |R| times n to the c time on general graphs would contradict the stated W[2]-hardness.
read the original abstract
Inspired by the potential of improving tractability via gap- or above-guarantee parametrisations, we investigate the complexity of Dominating Set when given a suitable lower-bound witness. Concretely, we consider being provided with a maximal r-independent set X (a set in which all vertices have pairwise distance at least r + 1) along the input graph G which, for r >= 2, lower-bounds the minimum size of any dominating set of G. In the spirit of gap-parameters, we consider a parametrisation by the size of the 'residual' set R := V (G) \ N [X]. Our work aims to answer two questions: How does the constant r affect the tractability of the problem and does the restriction to sparse graph classes help here? For the base case r = 2, we find that the problem is paraNP -complete even in apex- and bounded-degree graphs. For r = 3, the problem is W[2]-hard for general graphs but in FPT for nowhere dense classes and it admits a linear kernel for bounded expansion classes. For r >= 4, the parametrisation becomes essentially equivalent to the natural parameter, the size of the dominating set.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript studies the parameterized complexity of Dominating Set given a maximal r-independent set X as input, parameterized by the size of the residual set R = V(G) minus the closed 1-neighborhood of X. For r=2 the problem is shown to be paraNP-complete even on apex graphs and bounded-degree graphs. For r=3 it is W[2]-hard on general graphs, FPT on nowhere dense classes, and admits a linear kernel on bounded-expansion classes. For r>=4 the parameterization is equivalent to the standard solution-size parameterization.
Significance. If the stated complexity classifications hold, the work clarifies how the constant r modulates tractability under an above-guarantee parameterization and demonstrates that sparseness (nowhere dense / bounded expansion) yields algorithmic improvements only for specific small values of r. The results rely on standard parameterized reductions and kernelization techniques for sparse graphs; no machine-checked proofs or parameter-free derivations are claimed.
minor comments (2)
- [Abstract] Abstract, opening paragraph: the sentence defining R contains an extraneous space (V (G)); this is a minor typographical issue but should be corrected for clarity.
- [Abstract] Abstract: the claim that the parameterization 'becomes essentially equivalent' for r>=4 would benefit from a one-sentence justification (e.g., a short reduction showing |R| is bounded by a function of the domination number) even if the full argument appears later.
Simulated Author's Rebuttal
We thank the referee for the careful reading and the recommendation of minor revision. The report accurately summarizes the main results of the manuscript. No specific major comments or requests for changes were raised.
Circularity Check
No significant circularity; results rely on standard parameterized reductions
full rationale
The paper defines the problem directly as Dominating Set parameterized by |R| where R = V(G) minus N[X] and X is a given maximal r-independent set. The lower-bound |X| <= gamma(G) for r >= 2 follows immediately from the definition of r-independence (pairwise distances >= r+1 imply disjoint closed neighborhoods), which is a basic graph-theoretic observation stated in the abstract and not derived from any fitted quantity or self-citation. All complexity claims (paraNP-completeness for r=2, W[2]-hardness/FPT/kernel results for r=3, equivalence for r>=4) are obtained via explicit reductions and algorithms on the stated graph classes; no step renames a fitted input as a prediction, imports uniqueness via self-citation, or reduces a central claim to a tautology by construction. The derivation chain is therefore self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Standard definitions of dominating set, r-independent set, maximal independent set, and the parameterized complexity classes FPT, W[2], paraNP-complete.
Lean theorems connected to this paper
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IndisputableMonolith/Foundation/AbsoluteFloorClosure.leanabsolute_floor_iff_bare_distinguishability unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
For r = 3, the problem is W[2]-hard for general graphs but in FPT for nowhere dense classes and it admits a linear kernel for bounded expansion classes.
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We consider being provided with a maximal r-independent set X ... parametrisation by the size of the 'residual' set R := V(G) minus N[X].
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
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discussion (0)
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