Erdős Problem 750 #
References:
- erdosproblems.com/750
- [Er94b] Erdős, Paul, Some problems in number theory, combinatorics and combinatorial geometry. Math. Pannon. (1994), 261-269.
theorem
Erdos750.erdos_750 :
True ↔ ∀ (f : ℕ → NNReal),
Filter.Tendsto f Filter.atTop Filter.atTop →
∃ (V : Type u_1) (G : SimpleGraph V),
G.chromaticNumber = ⊤ ∧ ∀ (m : ℕ) (S : Set V), 0 < m → S.ncard = m → ∃ I ⊆ S, G.IsIndepSet I ∧ ↑m / 2 - f m ≤ ↑I.ncard
Let $f(m)$ be some function such that $f(m)\to \infty$ as $m\to \infty$. Does there exist a graph $G$ of infinite chromatic number such that every subgraph on $m$ vertices contains an independent set of size at least $\frac{m}{2}-f(m)$?
Note that in [Er94b] the function $f$ generalises a (proven) result for $f(m) = \epsilon m$, where $\epsilon > 0$. Hence we should assume it is non-negative valued.