Predicates on coordinate spaces in this section are treated classically when needed in piecewise definitions.
Equations
Instances For
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 textbook mixed-order comparison is equivalent to the two cross-closure identities.
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.
Helper for Text 34.0.1: once the normalized existential witness is available, the full idempotence and lower/upper closedness conclusion follows by the local closure chain already established in this file.
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.