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JCAAM IS A JOURNAL OF RAPID PUBLICATION Editorial Board Associate Editors Editor in -Chief: 19) Rupert Lasser George Anastassiou Institut fur Biomathematik & Biomertie,GSF Department of Mathematical Sciences -National Research Center for environment and The University Of Memphis health Memphis,TN 38152,USA Ingolstaedter landstr.1 tel.901-678-3144,fax 901-678-2480 D-85764 Neuherberg,Germany e-mail [email protected] [email protected] www.msci.memphis.edu/~ganastss/jcaam Orthogonal Polynomials,Fourier Analysis, Areas:Approximation Theory, Mathematical Biology Probability,Moments,Wavelet, Neural Networks,Inequalities,Fuzzyness. 20) Alexandru Lupas University of Sibiu Associate Editors: Faculty of Sciences Department of Mathematics 1) Ravi Agarwal Str.I.Ratiu nr.7 Florida Institute of Technology 2400-Sibiu,Romania Applied Mathematics Program [email protected] 150 W.University Blvd. Classical Analysis,Inequalities, Melbourne,FL 32901,USA Special Functions,Umbral Calculus, [email protected] Approximation Th.,Numerical Analysis Differential Equations,Difference and Methods Equations,inequalities 21) Ram N.Mohapatra Department of Mathematics 2) Shair Ahmad University of Central Florida University of Texas at San Antonio Orlando,FL 32816-1364 Division of Math.& Stat. tel.407-823-5080 San Antonio,TX 78249-0664,USA [email protected] [email protected] Real and Complex analysis,Approximation Th., Differential Equations,Mathematical Fourier Analysis, Fuzzy Sets and Systems Biology 22) Rainer Nagel 3) Drumi D.Bainov Arbeitsbereich Funktionalanalysis Medical University of Sofia Mathematisches Institut P.O.Box 45,1504 Sofia,Bulgaria Auf der Morgenstelle 10 [email protected] D-72076 Tuebingen Differential Equations,Optimal Control, Germany Numerical Analysis,Approximation Theory tel.49-7071-2973242 fax 49-7071-294322 4) Carlo Bardaro [email protected] Dipartimento di Matematica & Informatica evolution equations,semigroups,spectral th., Universita' di Perugia positivity Via Vanvitelli 1 06123 Perugia,ITALY 23) Panos M.Pardalos tel.+390755855034, +390755853822, Center for Appl. Optimization fax +390755855024 University of Florida [email protected] , 303 Weil Hall [email protected] P.O.Box 116595 Functional Analysis and Approximation Th., Gainesville,FL 32611-6595 Summability,Signal Analysis,Integral tel.352-392-9011 Equations, [email protected] Measure Th.,Real Analysis Optimization,Operations Research 5) Francoise Bastin 24) Svetlozar T.Rachev Institute of Mathematics Dept.of Statistics and Applied Probability University of Liege Program 4000 Liege University of California,Santa Barbara BELGIUM CA 93106-3110,USA [email protected] tel.805-893-4869 Functional Analysis,Wavelets [email protected] AND 6) Paul L.Butzer Chair of Econometrics and Statistics RWTH Aachen School of Economics and Business Engineering Lehrstuhl A fur Mathematik University of Karlsruhe D-52056 Aachen Kollegium am Schloss,Bau II,20.12,R210 Germany Postfach 6980,D-76128,Karlsruhe,Germany tel.0049/241/80-94627 office, tel.011-49-721-608-7535 0049/241/72833 home, [email protected] fax 0049/241/80-92212 Mathematical and Empirical Finance, [email protected] Applied Probability, Statistics and Econometrics Approximation Th.,Sampling Th.,Signals, Semigroups of Operators,Fourier Analysis 25) Paolo Emilio Ricci Universita' degli Studi di Roma "La Sapienza" 7) Yeol Je Cho Dipartimento di Matematica-Istituto Department of Mathematics Education "G.Castelnuovo" College of Education P.le A.Moro,2-00185 Roma,ITALY Gyeongsang National University tel.++39 0649913201,fax ++39 0644701007 Chinju 660-701 [email protected],[email protected] KOREA Orthogonal Polynomials and Special functions, tel.055-751-5673 Office, Numerical Analysis, Transforms,Operational 055-755-3644 home, Calculus, fax 055-751-6117 Differential and Difference equations [email protected] Nonlinear operator Th.,Inequalities, 26) Cecil C.Rousseau Geometry of Banach Spaces Department of Mathematical Sciences The University of Memphis 8) Sever S.Dragomir Memphis,TN 38152,USA School of Communications and Informatics tel.901-678-2490,fax 901-678-2480 Victoria University of Technology [email protected] PO Box 14428 Combinatorics,Graph Th., Melbourne City M.C Asymptotic Approximations, Victoria 8001,Australia Applications to Physics tel 61 3 9688 4437,fax 61 3 9688 4050 [email protected], 27) Tomasz Rychlik [email protected] Institute of Mathematics Math.Analysis,Inequalities,Approximation Polish Academy of Sciences Th., Chopina 12,87100 Torun, Poland Numerical Analysis, Geometry of Banach [email protected] Spaces, Mathematical Statistics,Probabilistic Information Th. and Coding Inequalities 9) A.M.Fink 28) Bl. Sendov Department of Mathematics Institute of Mathematics and Informatics Iowa State University Bulgarian Academy of Sciences Ames,IA 50011-0001,USA Sofia 1090,Bulgaria tel.515-294-8150 [email protected] [email protected] Approximation Th.,Geometry of Polynomials, Inequalities,Ordinary Differential Image Compression Equations 29) Igor Shevchuk 10) Sorin Gal Faculty of Mathematics and Mechanics Department of Mathematics National Taras Shevchenko University of Oradea University of Kyiv Str.Armatei Romane 5 252017 Kyiv 3700 Oradea,Romania UKRAINE [email protected] [email protected] Approximation Th.,Fuzzyness,Complex Approximation Theory Analysis 30) H.M.Srivastava 11) Jerome A.Goldstein Department of Mathematics and Statistics Department of Mathematical Sciences University of Victoria The University of Memphis, Victoria,British Columbia V8W 3P4 Memphis,TN 38152,USA Canada tel.901-678-2484 tel.250-721-7455 office,250-477-6960 home, [email protected] fax 250-721-8962 Partial Differential Equations, [email protected] Semigroups of Operators Real and Complex Analysis,Fractional Calculus and Appl., 12) Heiner H.Gonska Integral Equations and Transforms,Higher Department of Mathematics Transcendental University of Duisburg Functions and Appl.,q-Series and q-Polynomials, Duisburg,D-47048 Analytic Number Th. Germany tel.0049-203-379-3542 office 31) Ferenc Szidarovszky [email protected] Dept.Systems and Industrial Engineering Approximation Th.,Computer Aided The University of Arizona Geometric Design Engineering Building,111 PO.Box 210020 13) Dmitry Khavinson Tucson,AZ 85721-0020,USA Department of Mathematical Sciences [email protected] University of Arkansas Numerical Methods,Game Th.,Dynamic Systems, Fayetteville,AR 72701,USA Multicriteria Decision making, tel.(479)575-6331,fax(479)575-8630 Conflict Resolution,Applications [email protected] in Economics and Natural Resources Potential Th.,Complex Analysis,Holomorphic Management PDE,Approximation Th.,Function Th. 32) Gancho Tachev 14) Virginia S.Kiryakova Dept.of Mathematics Institute of Mathematics and Informatics Univ.of Architecture,Civil Eng. and Geodesy Bulgarian Academy of Sciences 1 Hr.Smirnenski blvd Sofia 1090,Bulgaria BG-1421 Sofia,Bulgaria [email protected] Approximation Theory Special Functions,Integral Transforms, Fractional Calculus 33) Manfred Tasche Department of Mathematics 15) Hans-Bernd Knoop University of Rostock Institute of Mathematics D-18051 Rostock Gerhard Mercator University Germany D-47048 Duisburg [email protected] Germany Approximation Th.,Wavelet,Fourier Analysis, tel.0049-203-379-2676 Numerical Methods,Signal Processing, [email protected] Image Processing,Harmonic Analysis Approximation Theory,Interpolation 34) Chris P.Tsokos 16) Jerry Koliha Department of Mathematics Dept. of Mathematics & Statistics University of South Florida University of Melbourne 4202 E.Fowler Ave.,PHY 114 VIC 3010,Melbourne Tampa,FL 33620-5700,USA Australia [email protected],[email protected] [email protected] Stochastic Systems,Biomathematics, Inequalities,Operator Theory, Environmental Systems,Reliability Th. Matrix Analysis,Generalized Inverses 35) Lutz Volkmann 17) Mustafa Kulenovic Lehrstuhl II fuer Mathematik Department of Mathematics RWTH-Aachen University of Rhode Island Templergraben 55 Kingston,RI 02881,USA D-52062 Aachen [email protected] Germany Differential and Difference Equations [email protected] Complex Analysis,Combinatorics,Graph Theory 18) Gerassimos Ladas Department of Mathematics University of Rhode Island Kingston,RI 02881,USA [email protected] Differential and Difference Equations JOURNAL OF CONCRETE AND APPLICABLE MATHEMATICS,VOL.2,NO.3,191-212, 191 2004,COPYRIGHT 2004 EUDOXUS PRESS,LLC Strong And Weak Solutions Of Abstract Cauchy Problems 1 Chung-Cheng Kuo Department of Mathematics, Fu-Jen University Hsin-Chuang, Taipei, Taiwan e-mail: [email protected] Sen-Yen Shaw Graduate School of Engineering, Lunghwa University of Science and Technology Gueishan, Taoyuan, Taiwan e-mail: [email protected] Running head: Strong and weak solutions of abstract Cauchy problems Abstract. Let α be a positive number, C be a bounded linear injection on a Banach space X, and let A : D(A) ⊂ X → X be a closed linear operator commuting with C. Under suitable conditions on A (such as, C−1AC = A, ρ(A)6=∅,D(A)=X),wediscussconnectionsamong: (i)Abeingthegenerator of an α-times integrated C-semigroup on X; (ii) the existence of unique strong solution of u0(t) = Au(t) + j (t)Cx, t > 0; u(0) = 0, for all x ∈ D(A); α−1 (iii) the existence of unique strong solution of v0(t) = Av(t)+j (t)Cx+j ∗ α α Cg(t), t>0; v(0)=0, for all x∈X; (iv) the existence of unique weak solution oftheabstractCauchyproblem: w0(t)=Aw(t)+j (t)Cx+j ∗Cg(t), t> α−1 α−1 0; v(0) = 0, for all x ∈ X. Here j (t) = tα/Γ(α+1) and g is any function in α L1 ([0,∞),X). Applications to concrete examples are also demonstrated. loc 2000 Mathematics Subject Classification: 47D60, 47D62. Key words and phrases: α-times integrated C-semigroup, generator, abstract Cauchy problem, strong solution, weak solution. 1 Introduction Let X be a Banach space with norm k · k, and let B(X) be the set of all bounded linear operators from X into itself. Consider the abstract Cauchy problem (ACP): (cid:26)u0(t)=Au(t)+f(t), t>0; (ACP(f,x)) u(0)=x, 1Research supported in part by the National Science Council of Taiwan. 192 C.KUO,S.SHAW where A : D(A) ⊂ X → X is a closed linear operator and f is an X-valued function on [0,∞). Let X denote the Banach space D(A) equipped with the graph norm 1 kxk = kxk+kAxk for x ∈ D(A). A function u is called a strong solution X1 of ACP(f,x) if u ∈ C1((0,∞),X)∩C([0,∞),X ) and satisfies ACP(f,x). In 1 the case where A is densely defined, u is called a weak solution of ACP(f,x) if u is continuous, and for every x∗ ∈ D(A∗) the function hu(·),x∗i is absolutely continuous and satisfies (cid:26) dhu(t),x∗i=hu(t),A∗x∗i+hf(t),x∗i,a.e.t>0; dt u(0)=x. The ACP is closely related to the theory of operator semigroups. Arendt [14, A-II, Theorem 1.1] proved that ACP(0,x) has a unique strong solution for every x ∈ D(A) if and only if the part A of A in X (i.e. the restriction of 1 1 A with domain D(A ) := {x ∈ D(A);Ax ∈ X }) generates a C -semigroup on 1 1 0 X . Moreover, these two conditions are also equivalent to that A generates a 1 C -semigrouponX,providedthatAhasnonemptyresolventsetρ(A)[14,A-II, 0 Corollary 1.2]. Ball [2] proved that A has dense domain and ACP(f,x) has a unique weak solution for every f ∈ L1([0,∞),X) and x ∈ X if and only if A generates a C -semigroup on X. 0 RecentlyDaviesandPang[3],MiyaderaandTanaka([16],[17]),deLauben- fels ([4], [5]) have studied C-semigroups (also called regularized semigroups) and their connections with the ACP. A result of deLaubenfels [4, Theorem 4.1] states that if A is the generator of a C-semigroup, then A commutes with C and ACP(0,x) has a unique strong solution for each initial value x in C(D(A)). TanakaandMiyadera[17,Corollary2.2]thenshowedthatincaseρ(A)6=∅,the converse of the last statement is also true. The aim of this paper is to prove generalizations of the aforementioned resultstoα-times(α>0)integratedC-semigroups. Thisclassisageneralization oftheclassofα-timesintegratedsemigroups,whichhavebeenstudiedin[1],[6], [8],and[15]forα∈N,and[7],[12],and[13]forα∈R . Thispaperservesasa + continuationof[9],inwhichbasicpropertiesofα-timesintegratedC-semigroups as well as characterization of their generators have been discussed. Let C ∈B(X) be an injective operator and α a positive number. A family S(·)={S(t);t≥0} in B(X) is called an α-times integrated C-semigroup if (1.1) S(·)x:[0,∞)−→X is continuous for each x∈X; (1.2) S(0)=0, S(t)C =CS(t), and for all x∈X, t, s≥0 1 (cid:18)Z t+s Z t Z s(cid:19) S(t)S(s)x= − − (t+s−r)α−1S(r)Cxdr. Γ(α) 0 0 0 An α-times integrated C-semigroup S(·) is said to be nondegenerate if (1.3) S(t)x=0 for all t>0 implies x=0. Note that for a nondegenerate α-times integrated C-semigroup, the identity S(0) = 0 follows automatically from (1.3) and the functional equation in (1.2) and so it is superfluous in condition (1.2) in the nondegenerate case.