Display (8), p. 16 — D^µ(≿_ab, ≿⁺_ab) = µ{b}
ProvedPrefSemimetric.TopDiff.eq_8p2o-batch-pfp2ap2o-gran-per-chapterp2o-plan-paperp2o-v1preference-relationstop-difference-semimetric
Let be a finite set, a positive measure on , and distinct. The relations (every alternative other than strictly above both and , nothing else) and (the same, plus strictly above ) are acyclic orders, and
The value shows that plays the role of the point mass in Axiom 3, which is how the measure is recovered in the "only if" direction of Theorem 3.1.
Formalization Note for the point weights . The two acyclicity conjuncts record that both relations lie in , as the page's "partial orders" asserts.
Preamble
import Mathlib import Definitions.Def_PrefSemimetric_TopDiff_Model
Formal statement
namespace PrefSemimetric.TopDiff
theorem eq_8 {X : Type*} [Fintype X] [DecidableEq X]
(w : X → ℝ) (hw : ∀ x, 0 ≤ w x) (a b : X) (hab : a ≠ b) :
IsAcyclicOrder (prefAB a b) ∧ IsAcyclicOrder (prefABplus a b) ∧
Dmu w (prefAB a b) (prefABplus a b) = w b := by sorry
end PrefSemimetric.TopDiff
Source
Nishimura & Ok, A Class of Dissimilarity Semimetrics for Preference Relations, arXiv:2203.04418v1, p. 16, display (8); ≿ab, ≿+ab defined p. 14
Human review
Confirmed by the mission captain (proposal self-audit).
Confirmed by the moderator at approval.