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Formalising the supersaturation theorem in Lean

Lean Action CI

This repository contains a formalisation of the supersaturation theorem in Lean. The statements of the results are as follows:

The supersaturation theorem

Suppose $\varepsilon > 0$ is a positive real number, and $G,H$ are simple graphs. If the number of vertices $v(G)$ is sufficently large and $G$ has at least $(\pi(H) + \varepsilon) \binom{v(G)}{2}$ many edges, then there exists a positive real number $\delta > 0$ such that $G$ contains at least $\delta \cdot v(G) ^ {v(H)}$ copies of $H$.

theorem labelledCopyCount_ge_of_card_edgeFinset {ε : ℝ} (hε_pos : 0 < ε) :
  ∃ δ > (0 : ℝ), ∃ N, ∀ n ≥ N, ∀ {G : SimpleGraph (Fin n)} [DecidableRel G.Adj],
    #G.edgeFinset ≥ (turanDensity H + ε) * n.choose 2 →
      G.labelledCopyCount H ≥ δ * n ^ card W

Upstreaming to mathlib

The progress towards upstreaming these results to mathlib is as follows:

  • The supersaturation theorem

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