Helper for Theorem 6.30.11: once a closed convex bifunction fails properness, its graph
function is an improper convex function on univ.
Helper for Theorem 6.30.11: once a closed concave bifunction fails properness, the negated
graph function is an improper convex function on univ.
Helper for Theorem 6.30.11: a closed improper convex bifunction graph can only take the
values ⊤ and ⊥.
Helper for Theorem 6.30.11: once a closed concave bifunction is improper, its negated graph
also takes only the values ⊤ and ⊥.
Helper for Theorem 6.30.11: if an improper convex bifunction graph is fixed by the current
Chapter 2 closure, then the bifunction must already be constant ⊤ or constant ⊥.
Helper for Theorem 6.30.11: if the negated graph of an improper concave bifunction is fixed by
the current Chapter 2 closure, then the bifunction must already be constant ⊤ or constant ⊥.
Helper for Theorem 6.30.11: in the closed improper nonconstant convex branch, the current Chapter 2 closure semantics force the failure of the desired fixed-point identity.
Helper for Theorem 6.30.11: in the closed improper nonconstant concave branch, the current Chapter 2 closure semantics force the failure of the desired fixed-point identity after negating the graph.
Helper for Theorem 6.30.11: a closed convex bifunction whose graph never attains ⊥
is fixed by the canonical graph closure. This is the graph-level lift of the Chapter 2
fixed-point theorem in the non-⊥ branch supported by the current closure API.
Helper for Theorem 6.30.11: a closed concave bifunction whose negated graph never attains
⊥ is fixed by the canonical concave graph closure. This is the concave counterpart of the
supported non-⊥ convex fixed-point theorem after negating the graph.
Helper for Theorem 6.30.11: in the convex branch, once the closure identity cl F = F is
supplied, the biconjugation formula immediately collapses to the fixed-point statement
F^{**} = F.
Helper for Theorem 6.30.11: in the concave branch, the fixed-point clause follows by
rewriting the biadjoint as the canonical concave closure and then using cl F = F.
Theorem 6.30.11: for a convex or concave bifunction F : ℝ^m → ℝ^n, its adjoint is a
closed bifunction of the opposite type from ℝ^n to ℝ^m, it is proper exactly when F is
proper, and the biadjoint agrees with the appropriate closure of F. The textbook closed-case
conclusion is formalized here through the explicit fixed-point identity cl F = F, i.e. through
the closure operator appearing in the preceding biconjugation statement itself. Closed proper
convex and closed proper concave bifunctions still correspond through adjunction, and
polyhedrality is preserved by adjoints.