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Difference between revisions of "Convex functional"

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====References====
 
====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  Z.W. Birnbaum,  W. Orlicz,  "Ueber die Verallgemeinerung des Begriffes der zueinander konjugierter Potenzen"  ''Studia Math.'' , '''3'''  (1931)  pp. 1–67</TD></TR><TR><TD valign="top">[2]</TD> <TD valign="top">  G.H. Hardy,  J.E. Littlewood,  G. Pólya,  "Inequalities" , Cambridge Univ. Press  (1934)</TD></TR><TR><TD valign="top">[3]</TD> <TD valign="top">  M.A. Krasnosel'skii,  Ya.B. Rutitskii,  "Convex functions and Orlicz spaces" , Noordhoff  (1961)  (Translated from Russian)</TD></TR><TR><TD valign="top">[4]</TD> <TD valign="top">  W. Fenchel,  "On conjugate convex functions"  ''Canad. J. Math.'' , '''1'''  (1949)  pp. 73–77</TD></TR><TR><TD valign="top">[5]</TD> <TD valign="top">  R.T. Rockafellar,  "Convex analysis" , Princeton Univ. Press  (1970)</TD></TR></table>
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<table><TR><TD valign="top">[1]</TD> <TD valign="top">  Z.W. Birnbaum,  W. Orlicz,  "Ueber die Verallgemeinerung des Begriffes der zueinander konjugierter Potenzen"  ''Studia Math.'' , '''3'''  (1931)  pp. 1–67 {{MR|}} {{ZBL|}} </TD></TR><TR><TD valign="top">[2]</TD> <TD valign="top">  G.H. Hardy,  J.E. Littlewood,  G. Pólya,  "Inequalities" , Cambridge Univ. Press  (1934) {{MR|2591337}} {{MR|1601748}} {{MR|1472649}} {{MR|1478445}} {{MR|1234454}} {{MR|1146141}} {{MR|1136994}} {{MR|0944909}} {{MR|0197653}} {{MR|0046395}} {{MR|0083530}} {{MR|0008854}} {{MR|1563622}} {{MR|1545539}} {{MR|1545530}} {{ZBL|0010.10703}}  {{ZBL|60.0169.01}} </TD></TR><TR><TD valign="top">[3]</TD> <TD valign="top">  M.A. Krasnosel'skii,  Ya.B. Rutitskii,  "Convex functions and Orlicz spaces" , Noordhoff  (1961)  (Translated from Russian) {{MR|}} {{ZBL|0095.09103}} </TD></TR><TR><TD valign="top">[4]</TD> <TD valign="top">  W. Fenchel,  "On conjugate convex functions"  ''Canad. J. Math.'' , '''1'''  (1949)  pp. 73–77 {{MR|0028365}} {{ZBL|0038.20902}} </TD></TR><TR><TD valign="top">[5]</TD> <TD valign="top">  R.T. Rockafellar,  "Convex analysis" , Princeton Univ. Press  (1970) {{MR|0274683}} {{ZBL|0193.18401}} </TD></TR></table>

Latest revision as of 11:58, 27 September 2012

A functional, defined on a convex subset of a linear vector space, the supergraph of which is a convex set. A functional which does not assume the value on a convex set is convex on if and only if the inequality

is satisfied. If the inequality sign is reversed, the functional is called concave. Operations which convert a convex functional into a convex functional include addition , multiplication by a positive number, taking the upper bound

and the infimal convolution

A convex functional bounded from above in a neighbourhood of some point is continuous at that point. If a convex functional is finite at some point , it has a (finite or infinite) derivative in any direction at that point. Closed convex functionals (i.e. functionals with convex and closed supergraphs) in locally convex linear topological spaces may be described in a dual way: Such a functional is the least upper bound of the affine functions which it dominates. This duality makes it possible to relate to each convex functional a dual object, the conjugate functional

Properties of convex functionals, operations on such functionals, and the relationship between a convex functional and its conjugate, are studied in convex analysis.

References

[1] Z.W. Birnbaum, W. Orlicz, "Ueber die Verallgemeinerung des Begriffes der zueinander konjugierter Potenzen" Studia Math. , 3 (1931) pp. 1–67
[2] G.H. Hardy, J.E. Littlewood, G. Pólya, "Inequalities" , Cambridge Univ. Press (1934) MR2591337 MR1601748 MR1472649 MR1478445 MR1234454 MR1146141 MR1136994 MR0944909 MR0197653 MR0046395 MR0083530 MR0008854 MR1563622 MR1545539 MR1545530 Zbl 0010.10703 Zbl 60.0169.01
[3] M.A. Krasnosel'skii, Ya.B. Rutitskii, "Convex functions and Orlicz spaces" , Noordhoff (1961) (Translated from Russian) Zbl 0095.09103
[4] W. Fenchel, "On conjugate convex functions" Canad. J. Math. , 1 (1949) pp. 73–77 MR0028365 Zbl 0038.20902
[5] R.T. Rockafellar, "Convex analysis" , Princeton Univ. Press (1970) MR0274683 Zbl 0193.18401
How to Cite This Entry:
Convex functional. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Convex_functional&oldid=28163
This article was adapted from an original article by V.M. Tikhomirov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article