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Books.ConvexAnalysis_Rockafellar_1970.Chap07.section34_part9

noncomputable def classicalDecidablePredPart9 {α : Type u_1} (p : αProp) :

Predicates on coordinate spaces in this section are treated classically when needed in piecewise definitions.

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      Helper for Text 34.1.4: after checking both the local-minimax route and the Section 33 uniqueness route, the unresolved dependency-closed blocker is exactly the original-text bridge cl₂ overline(K) = underline(K), from which the normalized raw mixed-order comparison follows formally.

      Helper bridge for Text 34.1.4: the exact upstream reverse-minimax input needed by the proof pipeline is precisely the normalized raw mixed-order inequality cl₂ (cl₁ K) ≤ cl₁ (cl₂ K). This theorem is just the dependency-closed package of the existing missing-prerequisite lemma, exposed under the name the later endgame uses conceptually.

      Helper for Text 34.1.4: once the normalized raw mixed-order comparison is supplied, the exact recovery cl₂ overline(K) = underline(K) follows formally from the already-proved local endgame.

      Helper for Text 34.1.4: the only remaining upstream prerequisite is now the mixed-order comparison underline(K) ≤ overline(K) for a bare concave-convex saddle-function.

      Helper for Text 34.1.4: after isolating the true upstream blocker to the mixed-order comparison, the exact recovery cl₂ overline(K) = underline(K) follows formally.

      Helper for Text 34.1.4: independently of the unresolved mixed-order comparison, the mixed upper closure always lies below cl₁ of the mixed lower closure.

      Helper for Text 34.1.4: once the mixed lower closure is known to lie below the mixed upper closure, first-variable closedness of the upper closure gives the reverse cl₁ bound.

      Helper for Text 34.1.4: the mixed-order comparison already forces the first cross-closure identity cl₁ underline(K) = overline(K).

      Helper for Text 34.1.4: once the mixed lower closure is known to lie below the mixed upper closure, second-variable closedness of the lower closure gives the reverse cl₂ bound.

      Helper for Text 34.1.4: the raw mixed-order inequality on cl₂ (cl₁ K) and cl₁ (cl₂ K) already packages the full concave-convex cross-closure conclusion.

      Helper for Text 34.1.4: once the exact recovery cl₂ overline(K) = underline(K) is known, both cross-closure identities follow immediately.

      Helper for Text 34.1.4: the full textbook pair of cross-closure identities is equivalent to the exact recovery statement cl₂ overline(K) = underline(K).

      Helper for Text 34.1.4: the first cross-closure identity already forces the textbook mixed-order comparison.

      Helper for Text 34.1.4: the full concave-convex textbook conclusion is equivalent to the raw operator inequality cl₂ (cl₁ K) ≤ cl₁ (cl₂ K).

      Helper for Text 34.1.4: after the lower recovery cl₂ overline(K) = underline(K) is known, the first cross-closure identity is the short textbook rewrite cl₁ underline(K) = cl₁ (cl₂ overline(K)) = overline(K).

      Text 34.1.4, qualified formal version: if K is concave-convex, its mixed closures are ordered, and the outer closures are fixed in their respective variables, then applying the opposite partial closures exchanges the mixed pair.

      Helper for Text 34.0.1: once the mixed lower closure is known to lie below the mixed upper closure, the two cross-closure identities follow from monotonicity and the one-sided fixed-point properties of the outer closures.

      Helper for Text 34.0.1: the first partial closure is unconditionally idempotent.

      Compatibility form of first-partial-closure idempotence for concave-convex kernels.

      Helper for Text 34.0.1: the second partial closure is unconditionally idempotent.

      Compatibility form of second-partial-closure idempotence for concave-convex kernels.

      Helper for Text 34.0.1: both mixed closures are fixed points of repeating the lower or upper closure operation.

      Helper for Text 34.0.1: a mixed lower closure is lower closed once the repeated lower closure operation fixes it.

      Helper for Text 34.0.1: an upper mixed closure is upper closed once the repeated upper closure operation fixes it.

      Helper for Text 34.0.1: the fixed-point forms package directly into the lower-closed and upper-closed conclusions for the two mixed closures.

      Text 34.0.1: for a concave-convex saddle-function, the iterated lower and upper closure operations are idempotent, and consequently the lower closure is lower closed while the upper closure is upper closed.

      Theorem 34.1: if K is any saddle-function on ℝ^m × ℝ^n, then its lower closure is a lower closed saddle-function and its upper closure is an upper closed saddle-function.