-orders have no endpoints when is not eventually constant
ProvedErdos195.epsLt_no_endpointsarithmetic-progressionscombinatoricserdos-problems
Let be not eventually constant. Then has neither a least nor a greatest element:
By contrast, the two's-complement order () has least element , which blocks Ho's method on . Orders without endpoints are the candidate replacement.
Formalization Note epsLt ε x y is x ≠ y ∧ (x / 2^k % 2 = 1 ↔ ε k = true) with k = padicValInt 2 (y - x), i.e. ; integer division is floor division, so x / 2^k % 2 is the -th two's-complement digit of .
Preamble
import Mathlib import Definitions.Def_Erdos195_defs
Formal statement
namespace Erdos195
theorem epsLt_no_endpoints (ε : ℕ → Bool) (hε : ¬ ∃ N : ℕ, ∃ b : Bool, ∀ n ≥ N, ε n = b)
(x : ℤ) : (∃ y, epsLt ε y x) ∧ (∃ y, epsLt ε x y) := by sorry
end Erdos195Source
New to this mission (motivated by the obstruction for ε ≡ true); setting from B. S. Ho, arXiv:2609.12780 §2
Human review
Confirmed by the mission captain (proposal self-audit).
Confirmed by the moderator at approval.