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Graph Pebbling in Coq

This repository holds the formalization of various graph pebbling results, which I produced over the course of my master's thesis (1). The Coq source is split over multiple files which are ordered by their prefix. The prefix starts with a a letter that indicates to which part the file belongs. There are four parts:

  • Part A - Utility library
  • Part B - General graph pebbling
  • Part C - Concrete pebbling bounds
  • Part D - Number theory constructions

This formalization was developed using Coq 8.16.0 and Coq-stdpp 1.8.0. To check the formalization, install the stdpp library (2) and run these commands:

coq_makefile -f _CoqProject -o CoqMakefile
make -f CoqMakefile

Results

Pebbling bound of a diameter-2 graph

Hypothesis undirected : Symmetric E.
Hypothesis weight2 : ∀ u v, weight G u v = 2.
Hypothesis diameter2 : ∀ u v, u = v ∨ E u v ∨ ∃ w, E u w ∧ E w v.

Theorem pebbling_bound_diameter_2 :
  pebbling_bound G (card V + 1).

Unidirectional solutions via pebble flows

Corollary pebble_flow_spec t n c :
  (∃ c', c -->* c' ∧ n ≤ c' t) ↔
  (∃ f, feasible c f ∧ unidirectional f ∧ n ≤ excess t c f).

Pebbling bound of an n-cube with generalized weights

Hypothesis ks_ge2 : Forall (λ k, k ≥ 2) ks.
Hypothesis ks_ord : ordered (≤) ks.

Corollary pebbling_bound_hypercube :
  pebbling_bound (hypercube n ks) (product ks).

Pebbling bound of n in the divisor lattice of n

Corollary vertex_pebbling_bound_divisor_lattice n (non_zero : Premise (n > 0)) :
  vertex_pebbling_bound (divisor_lattice n) n (top_divisor n).

The Erdős-Lemke conjecture

Corollary Erdos_Lemke_conjecture (l : list nat) d n :
  length l = d -> d > 0 -> n > 0 -> d ∣ n -> (∀ a, a ∈ l -> a ∣ n) ->
  ∃ l', l' ≠ [] ∧ l' ⊆+ l ∧ d ∣ summation l' ∧ summation l' ≤ n.

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