Taking the convex-function closure does not change the Fenchel conjugate.
The Fenchel conjugate is closed and convex.
theorem
section16_recessionFunction_fenchelConjugate_proper_posHom
{n : ℕ}
(f : (Fin n → ℝ) → EReal)
(hf : ProperConvexFunctionOn Set.univ f)
:
The recession function of a Fenchel conjugate is proper and positively homogeneous.
theorem
section16_recessionCone_epigraph_eq_epigraph_recessionFunction_fenchelConjugate
{n : ℕ}
(f : (Fin n → ℝ) → EReal)
(hf : ProperConvexFunctionOn Set.univ f)
:
(epigraph Set.univ (fenchelConjugate n f)).recessionCone = epigraph Set.univ (recessionFunction (fenchelConjugate n f))
The epigraph recession cone of a Fenchel conjugate is the epigraph of its recession function.
theorem
section16_infimalConvolutionFamily_fenchelConjugate_closed_and_attained_of_nonempty_iInter_ri
{n m : ℕ}
(f : Fin m → (Fin n → ℝ) → EReal)
(hf : ∀ (i : Fin m), ProperConvexFunctionOn Set.univ (f i))
(hri :
(⋂ (i : Fin m),
euclideanRelativeInterior n
((fun (x : EuclideanSpace ℝ (Fin n)) => x.ofLp) ⁻¹' effectiveDomain Set.univ (f i))).Nonempty)
:
(convexFunctionClosure (infimalConvolutionFamily fun (i : Fin m) => fenchelConjugate n (f i)) = infimalConvolutionFamily fun (i : Fin m) => fenchelConjugate n (f i)) ∧ ∀ (xStar : Fin n → ℝ),
infimalConvolutionFamily (fun (i : Fin m) => fenchelConjugate n (f i)) xStar = ⊤ ∨ ∃ (xStarFamily : Fin m → Fin n → ℝ),
∑ i : Fin m, xStarFamily i = xStar ∧ ∑ i : Fin m, fenchelConjugate n (f i) (xStarFamily i) = infimalConvolutionFamily (fun (i : Fin m) => fenchelConjugate n (f i)) xStar
Closedness and attainment for the infimal convolution of conjugates under the ri condition.