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ConvexAnalysisMonotoneOperators_BauschkeCombettes_2017.Chap12.Proposition_12_6

theorem ERealFunction.dom_infimalConvolution {H : Type u} [AddGroup H] (f g : H(Set.Ioi )) :
dom ((fun (f g : H(Set.Ioi )) (x : H) => infimalConvolution (fun (y : H) => (f y)) (fun (y : H) => (g y)) x) f g) = effectiveDomain f + effectiveDomain g

Proposition 12.6 (ii): for extended-real-valued functions that never take the value -∞, the domain of the infimal convolution is the Minkowski sum of the domains.

theorem ERealFunction.infimalConvolution_comm {H : Type u} [AddCommGroup H] (f g : HEReal) :

Proposition 12.6 (iii): infimal convolution is commutative.

theorem ERealFunction.hasContinuousAffineMinorantWithSlope_infimalConvolution {H : Type u} [NormedAddCommGroup H] [InnerProductSpace H] (f g : HEReal) (u : H) (hf : HasContinuousAffineMinorantWithSlope f u) (hg : HasContinuousAffineMinorantWithSlope g u) :
HasContinuousAffineMinorantWithSlope ((fun (f g : HEReal) (x : H) => infimalConvolution (fun (y : H) => f y) (fun (y : H) => g y) x) f g) u

Proposition 12.6 (i): if f and g admit continuous affine minorants with slope u, then their infimal convolution admits one with the same slope.

theorem ERealFunction.infimalConvolution_ne_bot_of_hasContinuousAffineMinorantWithSlope {H : Type u} [NormedAddCommGroup H] [InnerProductSpace H] (f g : HEReal) (u : H) (hf : HasContinuousAffineMinorantWithSlope f u) (hg : HasContinuousAffineMinorantWithSlope g u) (x : H) :
(fun (f g : HEReal) (x : H) => infimalConvolution (fun (y : H) => f y) (fun (y : H) => g y) x) f g x

Under the hypotheses of Proposition 12.6 (i), the infimal convolution never attains -∞.

Proposition 12.6 (iv): if f, g, and h admit continuous affine minorants with the same slope, then infimal convolution is associative on f, g, and h.