Advances in MATHEMATICAL ECONOMICS Managing Editors Shigeo Kusuoka Toru Maruyama University ofTokyo Keio Univeristy Tokyo,JAPAN Tokyo, JAPAN Editors Robert Anderson Jean-Michel Grandmont Norio Kikuchi University of California, CREST-CNRS Keio Univeristy Berkeley Malakoff, FRANCE Yokohama, JAPAN Berkeley, U.S.A. Norimichi Hirano Hiroshi Matano Charles Castaing Yokohama National Universityof Tokyo Universire Montpellier II University Tokyo, JAPAN Montpellier, FRANCE Yokohama,JAPAN Frank H. Clarke Leonid Hurwicz Kazuo Nishimura Universite de Lyon I University of Minnesota Kyoto University Villeurbanne, FRANCE Minneapolis, U.S.A. Kyoto, JAPAN Gerard Debreu Tatsuro Ichiishi Marcel K. Richter University of California, Ohio State University University of Minnesota Berkeley Ohio, U.S.A. Minneapolis, U.S.A. Berkeley, U.S.A. Alexander loffe Yoichiro Takahashi Egbert Dierker Israel Instituteof Kyoto University University of Vienna Technology Kyoto, JAPAN Vienna, AUSTRIA Haifa, ISRAEL Darrell Duffie Michel Valadier Seiichi Iwamoto Stanford University Universite Montpellier II Kyushu University Stanford, U.S.A. Montpellier, FRANCE Fukuoka, JAPAN Lawrence C. Evans Kazuya Kamiya Akira Yamazaki University of California, University of Tokyo Hitotsubashi University Berkeley Tokyo,JAPAN Tokyo, JAPAN Berkeley, U.S.A. Takao Fujimoto Kunio Kawamata Makoto Yano Kagawa University Keio Univeristy Keio Univeristy Kagawa, JAPAN Tokyo, JAPAN Tokyo, JAPAN Aims and Scope. The project is to publish Advances in Mathemat ical Economics once a year under the auspices of the Research Cen ter of Mathematical Economics. It is designed to bring together those mathematicians who are seriously interested in obtaining new challeng ing stimulifrom economic theoriesand thoseeconomistswhoare seeking effective mathematical tools for their research. The scope of Advances in Mathematical Economics includes, but is not limited to, the followingfields: - Economic theories in various fields based on rigorous mathematical reasoning. - Mathematical methods (e.g., analysis, algebra,geometry, probability) motivated by economic theories. - Mathematical results of potential relevance to economic theory. - Historical study ofmathematical economics. Authors are asked to develop their original results as fully as pos sible and also to give a clear-cut expository overview of the problem under discussion. Consequently, wewill also invite articles which might be considered too long for publication in journals. Springer Tokyo Berlin Heide/berg NewYork HongKong London Milan Palis s. Kusuoka, T. Maruyama (Eds.) Advances in Mathematical Economics Volume 5 i Springer Shigeo Kusuoka Professor Graduate School of Mathematical Seiences University ofTokyo 3-8-1 Komaba, Meguro-ku Tokyo, 153-0041 Japan Toru Maruyama Professor Department of Economics Keio University 2-15-45 Mita, Minato-ku Tokyo, 108-8345 Japan ISBN 4-431-00003-8 Springer-Verlag Tokyo Berlin Heidelberg New York Printed on acid-free paper Springer-Verlag is a company in the BertelsmannSpringer publishing group. @Springer-Verlag Tokyo 2003 Printed in Japan Thiswork issubjectto copyright.All rightsarereserved,whetherthewhole or part ofthe material isconcerned,specifically the rightsoftranslation,reprint ing, reuse ofillustrations, recitation, broadcasting,reproduction on microfilms or in other ways, and storage in data banks. The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Camera-ready copy prepared from the authors' ~TEXfiles. Printed and bound by Hirakawa Kogyosha, Japan. SPIN: 10898895 Table of Contents Research Articles G. Carlier Duality and existence for a dass of mass transportation problems and economic applications 1 C. Castaing, A. G. Ibrahim Functional evolution equations governed by m-accretive operators 23 T. Fujimoto, J. A. Silva, A. Villar Nonlinear generalizations oftheorems on inverse-positive matrices 55 1. Hurwicz, M. K. Richter Implicit functions and diffeomorphisms without Cl 65 1. Hurwicz, M. K. Richter Optimization and Lagrange multipliers: non-C'! constraints and "minimal" constraint qualifications 97 S. Kusuoka Monte Car10method for pricing of Bermuda type derivatives 153 Historical Perspective I. Mutoh Mathematical economics in Vienna between the VVars 167 Subject Index 197 Adv.Math. Econ.5, 1-21(2003) Advancesin MATHEMATICAL ECONOMICS ©Springer-Verlag2003 Duality and existence for a dass of mass transportation problems and economic applications Guillaume Carlier Universite Bordeaux I, MAB, UMR CNRS 5466 and Universire Bordeaux IV, GRAPE,UMRCNRS5113,AvenueLeon Duguit,33608, Pessac,FRANCE (e-mail:[email protected]) Received:April 15,2002 Revised:May 20,2002 JELcIassification:C61,C82 MathematicsSubjectClassification (2000): 90C08, 90C46, 91B40 Abstract We establish duality, existence and uniqueness results for a class of mass transportations problems. We extend a technique of W.Gangbo [9] using the Euler Equationofthedualproblem.Thisisdone byintroducingthe h-FenchelTransformand usingitsbasicproperties.The costfunctionsweconsidersatisfyageneralizationofthe so-calledSpence-Mirrleesconditionwhichiswell-known byeconomistsindimension I.Wethereforeend thisarticle byasomehow unexpectedapplication tothe economic theoryofincentives. Key words: mass transportation,duality,generalFencheltransform, economictheory ofincentives, Spence-Mirrleescondition 1. Introduction and main statement 1.1 Assumptionsand notations Let us first recall that, given a probability space (Ol,Al,lll), a measurable space (02,A2) and a measurable map f :01 --> O2, the push-forward of 111 through f,denoted fUlll istheprobability measureon (02,A2) defined by: forevery B EA2. S. Kusuoka, et al. (eds.), Advances in Mathematical Economics © Springer-Verlag Tokyo 2003 2 G.Carlier In allthefollowing, nissome boundedconnectedopen subset ofIRn, and J-l is some probability measure in n which is absolutely continuous with re specttothen-dimensionalLebesguemeasure, withapositiveRadon-Nikodym derivative with respect to the n-dimensional Lebesgue measure and such that J-l(Bn) = O. Weare also givenacompactPolish space Y,aRadonprobabilitymeasure v on Y andafunction h :0 x Y --+ IRwhich satisfies: hE 0°(0 x Y,IR), (I) foreverywce nthere exists c(w)> 0such that forall (Xl,X2) Ew2 sup Ih(XI'y) - h(X2,y)1 :::; c(w)llxI - x211, (2) yEY forallYE Y, h(.,y)isdifferentiableinnandforall (YI'Y2,x) E y2Xn Bh Bh Bx(x,Yd = Bx(x,Y2)=> YI =Y2· (3) Assumption (3) playsan importantrole intheproofs and we shall seethat it maybe interpretedasageneralization ofthe well-known oneofSpence and Mirrlees, thisassumption wasfirstintroducedbyLevin in[13]. Our aim istostudy the following Monge's mass transportationproblem: r (M) sup J(s) := h(x,s(x))dJ-l(x) Jo sEtl(J.!,v) with: D..(J-l,v) := {s isaBorel map :n--+ Y s.t.sttJ-l = v}. The associated Monge-Kantorovich problem is the linear (relaxation of (M)) program: r (MK) sup K('y):= h(x,y)d'Y(x,y) , Er(J<,v) JOXY with: r(J-l,v) := bisaBorel probabiliymeasure onnxY S.t.1Tlh = J-l, 1T2h = v} where1TI(x,y) = x,1T2(X,y) = Yforall (x,y) E nx Y. Finally, wedefinethe (dual of (M)) problem: with: Eh := {(vJ,c/» ,real-valued measurables.t,vJ(x)+c/>(Y) ~ h(x,y),V(x,y) E nxY}. Dualityandcxistcncc foradassofmasstransportationproblems 3 1.2 Main result If 'l/J is a given real-valued function defined on n,we define the h-Fenchel Transforrnof'l/J,'l/Jhby: 'l/Jh(y):= suph(x,y)- 'l/J(x), forall y E Y. xEIl In a similar way, if r/J is a given real-valued function defined on Y, we define the h-FenchelTransforrn ofr/J,r/Jhby: r/Jh(x):= sup h(x,y) - r/J(y), forallx E n. yEY Our mainresult can then bestatedasfolIows: Theorem 1 Underassumptions(1),(2),(3)thefollowingassertionshold: 1)problems(M),(M K) and(V )admitatleastonesolution, 2) (V )isdualto(M) and(M K) inthesense: inf'(D) = sup(M ) = sup(MK), 3) theminimumin(V) isattainedbyapair(~,([» suchthat: - -h - - h l/; = r/J ,r/J ='l/J thereexistsmoreoversomeBorelmapsfromnto Y whichsatisfies: ~(x) +([>(s(x)) = h(x,s(x)),jorallx E n, s E/:'(J-l,v)andisasolution of (M ),and(id,s)UJ-l isasolutionof(M K), 4) uniqueness also holds: if s is a solution of(M ) then s = s u-a.e., (id,s)UJ-l is the unique solution of(M K), and if ('l/J,r/J) is a solution of(V) thenib- ~(respectivelyr/J - ([» isequaltosomeconstantu-a.e.(respectively v-a.e.). In Section 2, technical lemmas are established and basic properties of the h-Fencheltransforrnareproved.InSection3,the mainresult isproved.Finally, inSection4,weadressaquestion arising intheeconomictheory ofincentives andshow how assumption(3) canbe interpreted as anaturalgeneralizationof the Spence-Mirrlees condition. In this framework, our main result enables to proveageneralre-allocation principle. The problem ofoptimal measure preserving maps (M) has received a lot of attention since related questions naturally arise in fluid mechanics [2], dif ferential geometry (see [16]for relationwith aclassical resultof Aleksandrov 4 G.Carlier [1]), shapeoptimization[4],functionalanalysis[11], [12],probability[19]and economics.InthecaseY C IRn and h(x,y) = x'y,theproblemwassolvedby Brenier [3] who proved the important Polar Factorization Theorem and exis tenceand uniquenessofanoptimal map which isthe gradientofsomeconvex potential.This resultwasthen extendedbyMc Cann and Gangbo[10] forcosts of the form c(x - y)with cstrictlyconvex.The result stated inTheorem 1,is very much inthat spiritsince itexpressesexistenceand uniquenessof anopti mal allocation map which isameasurableselectionofthe h-subdifferential of some h-convex potential. Similarcharacterization results were obtained by V. Levin [13] using a different approach based on cyclical monotonicity and the relaxed problem (MK). 2. Technical preliminaries andh-Fenchel transform In what follows7/J will alwaysdenotesome function :0 -t IRU{+00}and </> somefunction :Y -t IRU{+oo}. Definition1 J) 7/J is h-convex ifandonlyifthereexistsanonemptysubset A ofY x IRsuchthat: 7/J(x)= sup h(x,y)+t,foralt xE O. (y,t)EA 2) </>ish-convexifandonlyifthereexistsanonemptysubsetB of O x IRsuch that: </>(y)= sup h(x,y)+t,foralty E Y. (x,t)EB Remark. If 7/J is h-convex then either 7/J is identically +00 or it is bounded. Notealso that finite k-convexpotentialsare l.s.c, hence z--measurable. __ Definition2 I) The h-Fenchel Transformof7/J, 7/Jh, is the h-convexfunction definedby: 7/Jh(y):= sup h(x,y)- 7/J(x),for alty E Y. xE!! 2)Thek-FenchelTransformof </>, </>h istheh-convexfunctiondefinedby: qi (x) := suph(x,y)- </>(y),for altx EO. yEY Obviously,Young'sinequalitieshold: 7/J(x)+7/Jh(y) ~ h(x,y), for all (x,y) E 0 x Y (4) and: </>h(x)+</>(y) ~ h(x,y), for all (x,y)E 0 x Y. (5) Duality andexistence foradassofmasstransportation problems 5 Proposition 1 (7j;h)h(x) = sup{J(x):f :S 7j;. fis h-convex},foraltx Efl, (qi)h(y) = sup{g(x) :g :S 4>. fis h-convex},foralty E Y. Itfoltowsthat7j;(respectively4» ish-convex(respectivelyh-convex)ifandonly if1j; = (7j;h)h (respectively4> = (4)h)h). Proof. First (7j;h)h is h-convex and Young's inequality yields (1j;h)h :S 7j; so that, ifwedefine: V(x) := sup{J(x) :f :S 7j;, f ish-convex },for allx Efl, (6) then : (7) Since V ish-convex, there exists anonemptysubset Aof Y x IRsuch that: V(x)= sup h(x,y)+t,foraII xEfl. (y.t)EA Let (Yo,to) E Aand ~ := h(.,Yo) + towe have: J/J ~ ~ =? (7j;h)h ~ (~h)h (8) ofcoursef ~ (~h)h andsincee(Yo) = - tothen (~h)h(x) ~ h(x,yo)+to = ~(x) for all x so (~h/' = ~, with (8) we get (7j;h)h ~ ~ and since (Yo,to) is arbitrary in A taking the supremum yields (J/Jh/, ~ V so that V = (7j;h)h using (7).The characterization of (4)h)h isproved inthesame way. o Definition3 I)Define,for altx E fl: {)h7j;(X):= {y E Y:7j;(x')- J/J(x)~ h(x',y) - h(x,y), foralt x' E fl} {)h7j;(x)iscaltedtheh-subdifferentialof7j; atz,and1j; is h-subdifferentiable atx ifandonlyif{)hJ/J(x) -I- 0. 2)Define,for alty E Y: {)h4>(Y):= {x En:4>(y')- 4>(y) ~ h(x,y') - h(x,y), foralty' E Y}.