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Preliminary
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Theorem I.1 Hahn-Banach, analytic form
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Minkowski gauge Theorem
Let K be a convex set in E with 0 being its interior point. Define a function
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Proof of Minkowski gauge Theorem p.1
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Proof of Minkowski gauge Theorem p.2
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Minkowski gauge function of K
is called the Minkowski gauge function of K
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Lemma 1
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Proof of Lemma 1 p.1
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Proof of Lemma 1 p.2
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Remark
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Proof of Remark p.1
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Hyperplane E:real vector space is called a Hyperplane of equation[f=α]
If α=0, then H is a Hypersubspace
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Proposition 1.5 E: real normed vector space
The Hyperplane [f=α] is closed if and only if
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Theorem 1.6(Hahn-Banach; the first geometric form)
E:real normed vector space Let be two disjoint nonnempty convex sets. Suppose A is open, then there is a closed Hyperplane separating A and B in broad sense.
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Epigraph E : set Epigraph, is the set
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Conjugated function Assume that E is a real n.v.s Given such that
Define the conjugated function of by
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Theorem I.11 see next page Suppose and are convex and suppose that
there is such that and is continuous at
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Observe (1) usually appears for constrain (2) see next page
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The proof of Thm I.11 see next page
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Application of Thm I.11 Let be nonempty, close and convex. Put
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Let
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Application of Hahn-Banach Theorem
E: real normed vector space G: vector subspace Then for any
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Theorem II.5 (Open Mapping Thm,Banach)
Let E and F be two Banach spaces and T a surjective linear continuous from E onto F. Then there is a constant c>0 such that
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Theorem II.8 Let E be a Banach space and let G and
L be two closed vector subspaces such that G+L is closed . Then there exists constant such that
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(13) any element z of G+L admits a
decomposition of the form z=x+y with L x G z y
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Corollary II.9 Let E be a Banach space and let G and
L be two closed vector subspaces such that G+L is closed . Then there exists constant such that
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(14) L G x
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II.5 Orthogonolity Relation
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are closed vector subspace
X: Banach space : vector subspace orthogonal of M : vector subspace Let are closed vector subspace of X and X’ ,respectively.
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Proposition II.12 Suppose M is a vector subspace of X then
If N is a vector subspace of then
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Proposition II.13 Suppose G and L are closed vector
subspaces of X. We have (16) (17)
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Corollary II.14 Suppose G and L are closed vector
subspaces of X. We have (18) (19)
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Proposition II.15 p.1 Suppose G and L are closed vector
subspaces of X. The following properties are equivalent:
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Proposition II.15 p.2 (a) G+L is closed in X. (b) is closed in X´ (c)
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II.5 Orthogonolity Relation
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Theorem I.11 see next page Suppose and are convex and suppose that
there is such that and is continuous at
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