Gen. Math. Notes, Vol. 26, No. 2, February 2015, pp. 104-118 ISSN 2219-7184; Copyright © ICSRS Publication, 2015 www.i-csrs.org Available free online at http://www.geman.in On - - -Contraction in Fuzzy Metric Space and its Application Noori F. AL-Mayahi1 and Sarim H. Hadi2 1,2 Department of Mathematics, University of AL–Qadissiya College of Computer Science and Mathematics 1 E-mail: afm2005@yahoo.com 2 E-mail: sarim.h2014@yahoo.com (Received: 11-8-14 / Accepted: 3-11-14) Abstract The aim of this paper is to introduce new concepts of - -complete fuzzy metric space and - -continuous function and establish fixed point results for - -contraction function in - -complete fuzzy metric space. As an application, we derive some Suzuki type fixed point theorems, fixed point in orbitally fcomplete. Moreover, we introduce concept - - -contraction function and application on - - -contraction. Keywords: - -complete, - -continuous, - - -contraction, orbitally fcomplete, Suzuki Type Fixed Point Result, - - -Contraction Function, Application on - - -Contraction. 1 Introduction The study of fixed points of functions in a fuzzy metric space satisfying certain contractive conditions has been at the center of vigorous research activity. In 1965, the concept of fuzzy sets was introduced by Zadeh [10]. With the concept of fuzzy sets, the fuzzy metric space was introduced by I. Kramosil and J. Michalek On - - -Contraction in Fuzzy Metric Space… 105 [5] in 1975. Helpern [3] in 1981first proved a fixed point theorem for fuzzy functions. Also M.Grabiec [2] in 1988 proved the contraction principle in the setting of the fuzzy metric spaces. Moreover, A. George and P. Veeramani [1] in1994 modified the notion of fuzzy metric spaces with the help of t-norm. This paper we introduce new concepts of - -complete fuzzy metric space and - -continuous function and establish fixed point results for - - -contraction function in - -complete fuzzy metric space. As an application, we derive some Suzuki type fixed point theorems, fixed point in orbitally -complete. Moreover, we introduce concept - - -contraction function and application on - - contraction. 2 Preliminaries Definition 2.1 [4]: Let : → and : to be -admissible function if , )≥1 ⟹ ), Definition 2.2 [6]: Let : → and said to be , )-admissible function if , )≥1 , )≥1 ), ⟹ ), × → [0, ∞) be two function, ) ≥ 1 for all , , : × is said ∈ . → [0, ∞) be two function, is ) ≥1 for all , ) ≥1 ∈ . Definition 2.3 [4]: Let : → and , : × → [0, ∞) be two function, said to be -admissible function with respect if , )≥ , ) ⟹ Not that if we take Definition 2.4: Let { , : × % } with Note: ), )) ≥ )) , for all , ∈ , ) = 1 , then this definition reduces to definition (2.1 ). , ",∗) be a fuzzy metric space and → [0, ∞) , is said to be - -complete iff every Cauchy sequence % , %'( ) ≥ % , %'( ) for all ) ∈ ℕ converge in is said to be -complete if Example 2.5: Let = [0,1+ and " , ) = 1 for all , , )= + )8 6 , 0 6 9. : - ∈ . , , ,) = -'|/01| , if , > 0 with 3 ∗ 4 = 56) {3, 4} for every 3, 4 ∈ [0,1+ , define , : By ), is ∈ × → [0, ∞) 106 Noori F. AL-Mayahi et al. , )=2 Then , ",∗) is - -complete fuzzy metric space. Definition 2.6: Let , ",∗) be a fuzzy metric space and let , : × → [0, ∞) and : → , is said to be - -continuous function on if for ∈ and { % } be a sequence in with % → as ) → ∞ , % , %'( ) ≥ % %'( ) for all ) ). ) ∈ ℕ implies % → Definition 2.7 [9]: (1) Let be a function of a fuzzy metric space , ",∗) into itself. , ",∗) is said to be -orbitally complete if and only if every Cauchy sequence which is contained in { , ), 8 ), = ),· · · } for some ∈ converges in . A -orbitally complete fuzzy metric space may not be complete. (2) A function : → is called orbitally continuous at ) implies ?65%→@ % ) = The function ∈ . is orbitally continuous on if ∈ if ?65%→@ % )= is orbitally continuous for all Remark 2.8: (1) Let , ",∗) be a fuzzy metric space and : → be a function and let an orbitally -complete. Define , : × → [0, ∞) by 3 6 , )=A 1 , ∈ C :) , 9. : Where C :) is an orbit of a point : ∈ If { % } be a Cauchy sequence with { % } ∈ C :) . be , )=1 , ",∗) is an - -complete. % , %'( ) ≥ % , %'( ) for all ) ∈ ℕ then Now, since is an orbitally -complete fuzzy metric space, then { . We can say that is - -complete. %} converge in (2) Let , ",∗) and , : × → [0, ∞) is in (1), let : → be an orbitally continuous function on , " ∗). Then is - -continuous function. Indeed if → 3D ) → ∞ and % % , %'( ) ≥ % %'( ) for all ) ∈ ℕ, so % ∈ C :) for all ) ∈ ℕ , then there exist sequence EF )F∈ℕ of positive integer such that % → GH : → as 6 → ∞. Now since is an orbitally continuous on , ",∗), then GH :)) → ) 3D 6 → ∞. %) = On - - -Contraction in Fuzzy Metric Space… Denote with properties: (1) (2) 107 : [0,1+ → [0,1+ with the following the set of all the function is nondecreasing and continuous I) = 0 6 I = 1 Definition 2.9: Let , ",∗) be a fuzzy metric space and : → , let J , ) = ), ,), " , ), ,), " , ), ,) ∗ " , ), ,)} 56) {" , , ,), " , We say (1) is an - - -contraction function if ), ), ,) ≥ , )≥ , )⟹ " (2) is - -contraction function if J , )). , ) = 1 for all , ∈ . Theorem 2.10: Let , ",∗) be a fuzzy metric space and let : → , suppose that , : × → [0, ∞) are two function. Assume that the following assertions hold (i) (ii) (iii) (iv) (v) , ",∗) is an - -complete fuzzy metric space . is an -admissible function with respect to . is - - -contraction function on . is an - -continuous function . There exist K ∈ such that K, K )) ≥ K, Then has a fixed point in Proof: Let K ∈ % = %'( Suppose Since % %} % such that for some ) , then ≠ K) K, such that Define a sequence { If . = = % ≥ %0( ) K )) ≥ (, 8) Then K) K, for all ) ∈ ℕ is a fixed point of . %'( is -admissible function with respect K, K )). K, = K )) K ), () ≥ and K ), () = (, 8) By continuing this process, we get %, % )) = % , %'( ) ≥ % , %'( ) = %, % )) 108 Noori F. AL-Mayahi et al. By 1) in definition (2.9) " Where J %0( , %) % , %'( , ,) = 56) {" = 56) {" ≥ 56) {" Since " " %0( , % , ,), " " % ), ,) %0( , % ), ,) %0( , % , %'( , ,), " ≥ ∗" ∗" %, %0( , % ) %, %0( ), ,)} % , %'( , ,), " % , % , ,)} %0( , % , ,) % , %'( , ,)} J %0( ), ,), " %0( , % , ,), " %0( %'( , ,) %0( , % , ,), " ∗" % ), ,), % , %'( , ,), % , %'( , ,)} is nondecreasing and continuous, we have % , %'( , ,) If 56){" Then " %, %0( , % , ,), " %0( , % , ,), " = 56) {" %0( ), =" ≥ 56){" %0( , % , ,), " %'( , ,) %0( , % , ,), " % , %'( , ,)} ≥ 56){" %0( , > " % , %'( , ,) % , %'( , ,)}) =" % , %'( , ,) % , ,), " % , %'( , ,)}) ≥ " % , %'( , ,) Which is contradiction. Therefore 56){" %0( , % , ,), " " " % , %'( , ,)} Hence for all ) ∈ ℕ we have % , %'( , ,) ≥ %0( , % , ,) Let ), 5 ∈ ℕ with ) > 5 , then " % , N , ,) ≥ " Therefore ?65%→∞ " Hence { %} 8 " ≥⋯≥ % ≥⋯≥ %0( , % , ,) % , N , ,) ≥ % " =" %0( , % , ,) %08 , %0( , ,) K , ( , ,) =1 " K , ( , ,) is a Cauchy sequence Since is an - -complete fuzzy metric space there is )→∞. Since is an - -continuous function so %'( = %) ∈ → such that % ) as ) → ∞ → as On - - -Contraction in Fuzzy Metric Space… Hence )= Suppose is a fixed point of ), " , , ,) = " Hence = , )=| − |, all , ∈ I) = √I for all I ∈ [0,1+. Define " and , > 0 , and , : + )8 6 , 0 6 9. : , )=2 , , )= By J , )) = [0,3+ be equipped with the ordinary metric Example 2.11: Let O )= such that ), ,) ≥ 109 × ∈ → [0, ∞) , , ,) = R 0 S|TUV| W for Clearly, , ",∗) is an - - complete fuzzy metric space with respect to , −norm 3 ∗ 4 = 34. (by [8]) Let : → be defined as )= O ), It follows that " 1 ∈ [0,1+ =0/ 8 ∈ 1,3+ ) =| ), )− ), ,) = R 0 )| = 1 | − |≤| − |=O 2 S|Y T)UY V))| W ≥ R0 |TUV| W = , ) J , )) Thus f is α-η-φ-contraction function in fuzzy metric space X, M,∗). Corollary 2.12: Let , ",∗) be a fuzzy metric space and let : → , suppose that , : × → [0, ∞) are two function. Assume that the following assertions hold: (i) (ii) (iii) (iv) (v) , ",∗) is an -complete fuzzy metric space . is an -admissible function . is - -contraction function on . is an -continuous function . There exist K ∈ such that K, K )) ≥ 1. Then has a fixed point in . 110 Noori F. AL-Mayahi et al. Theorem 2.13: Let , ",∗) be a fuzzy metric space and let : → , suppose that , : × → [0, ∞) are two function. Assume that the following assertions hold: , ",∗) is an -complete fuzzy metric space is an -admissible function with respect to . is - - -contraction function on . There exist K ∈ such that K, K )) ≥ K, ) If { % } is a sequence in , ≥ , % %'( % %'( ) (i) (ii) (iii) (iv) (v) % With → as ) → ∞, then % ), Either % ), 8 Or Then )≥ )≥ 8 K ∈ K, such that Define a sequence { %} in 8 % ), . has a fixed point in Proof: Let % ), % by = = % )) % )) K) for all ) ∈ ℕ ≥ K) % = ∈ Let " Either 8 %0( ), )≥ %, )≥ %0( ), Then either Or Let " %'( , %, %'( , )≥ )≥ min {" )≥ as ) → ∞ %0( ), 8 %0( ), = % , %'( ) %0( ) for all ) ∈ ℕ. %'( , % ) ≥ %'( , % ) %0( )) %0( )) %'( , %'8 ) ), ,) = " %, 8 % , %'( ) Where J % , ) = 56) {" = → ), ,) ≠ 1 , from (v) , Or % such that K) K, Now is in the proof of theorem (2.10) we have There exist K )). from definition (2.9) condition (1), we get % ), ), ,) ≥ J , ,), " % , % ), ,), " ), ,) ∗ " , " %, %, , ,), " %, ) ), ,), , % ), ,)} ), ,), , ), ,) ∗ " , %'( , ,)}) % , %'( ,), " " %, On - - -Contraction in Fuzzy Metric Space… > 56){" %, , ,), " % , %'( ,), " , By taking ) → ∞ in the above we get ), ,) = 56) {1, " , " , 111 ), ,), " %, ), ,) ∗ " , ), ,)}) > " , %'( , ,)} ), ,) Which is contradiction. Hence " , ), ,) = 1 ⟹ )= . Corollary 2.14: Let , ",∗) be a fuzzy metric space and let : → , suppose that , : × → [0, ∞) are two function. Assume that the following assertions hold: (i) (ii) (iii) (iv) (v) With , ",∗) is an -complete fuzzy metric space. is an -admissible function. is - -contraction function on X. There exist K ∈ such that K, K )) ≥ 1. ) , If { % } is a sequence in % %'( ≥ 1 % → as ) → ∞, then Either Or Then 8 % ), % ), )≥1 ) ≥ 1 for all ) ∈ ℕ has a fixed point in . Corollary 2.15: Let , ",∗) be a complete fuzzy metric space and let : be a continuous function such that is contraction function that is " Then 2.2 ), ), ,) ≥ has a fixed point in . J , ) for all , ∈ Fixed Point in Orbitally c- Complete Fuzzy Metric Space Theorem 2.2.16: Let , ",∗) be a fuzzy metric space and : following assertion hold: (i) (ii) (iii) → → such that the , ",∗) is an orbitally -complete fuzzy metric space. ), ), ,) ≥ J , )) for there exist be a function such that " all , ∈ C :) for some : ∈ . If { % } be a sequence .such that { % } ⊆ C :) with % → as ) → ∞, ∈ C :). Then has fixed point in . 112 Noori F. AL-Mayahi et al. Proof: Define : × → [0, ∞) from remark (2.8) , fuzzy metric space and is an -admissible function. , ) ≥ 1 for all , Let Then from (ii) " ), ), ,) ≥ J , )) is an - -contraction function Let { sequence such that So { %} Then % , %'( ) ⊆ C :) from (iii) we have %, That is -complete ∈ C :) That is %} , ",∗) is an ≥ 1 with ∈ C :) % → ) ≥ 1 by corollary (2.13) has unique fixed point in . Corollary 2.2.17: Let , ",∗) be a fuzzy metric space and : the following assertion hold: → such that X, M,∗) is an orbitally f-complete fuzzy metric space. there exist k ∈ 0,1) such that M f x), f y), t) ≥ kJ x, y) for all x, y ∈ O w) for some w ∈ X. If {xk } be a sequence such that {xk } ⊆ O w) with xk → x as n → ∞. Then x ∈ O w). Then f has fixed point in X. (i) (ii) (iii) 2.3 Suzuki Type Fixed Point Result From Theorem (2.10) we deduce the following Suzuki type fixed point result Theorem 2.3.18: Let , ",∗) be a complete fuzzy metric space and let : continuous function .Assume that there exist E ∈ 0,1) such that " , For all , Then ), ,) ≥ " , , ,) ⟹ " ∈ , where ), J , ) = 56) {" , , ,), " , ), ,) ∗ " " , has a fixed point in Proof: Define , : × . ), ,) ≥ EJ , ) ____(1) ), ,), " , ), ,)} , → [0, ∞) and : [0,1+ → [0,1+ by ), ,), → On - - -Contraction in Fuzzy Metric Space… , )=" Such that , , )≥ ), ,) , )=" , , ) for all , I) = EI , I ∈ [0,1+ And let ∈ 113 , , ,) By condition (i) –(v) of theorem (2.10 ) Let Then " , , ) ≥ , ) ), ,) ≥ " , , ,) From (1) we have " ), ), ,) ≥ EJ , ) = J , )) Then is - - -contraction function by condition of theorem (2.10) and fixed point, then the unique fixed point follows from (1). Corollary 2.3.19: Let , ",∗) be a complete fuzzy metric space and let : continuous function. Assume that there exist E ∈ 0,1) such that ), ,) ≥ " , , ,) ⟹ " " , For all , ∈ , ), . has a fixed point in 2.4 An - l- m-Contraction Function Definition 2.4.20: Let , ",∗) be a complete fuzzy metric space. Let : an -admissible which satisfies the following ), ), ,) ≥ → ), ,) ≥ E" , , ,) Then " has J , ) − → be → be J , )) Such that (i) (ii) is continuous and decreasing with I) = 0 iff I = 1. is continuous with I) = 0 iff I = 1 is called - - - contraction function . Theorem 2.4.21: Let , ",∗) be a complete fuzzy metric space . Let : an -admissible which satisfies the following " ), ), ,) ≥ J , ) − J , )) 114 Noori F. AL-Mayahi et al. Such that , ",∗) is an -complete. is -continuous function There exist K ∈ such that (i) (ii) (iv) Proof: Let K ∈ Define a sequence { If = % % %} % such that for some ) , then %'( Suppose K, such that ≠ = K, K )) = % ≥1 K )) %0( ) K, K )) %'( = (, 8) Then for all ) ∈ ℕ is a fixed point of . is -admissible function with respect Since ≥ 1. K, () ≥1 K ), = () and K ), ≥ () (, 8) = By continuing this process, we get % )) %, Where J %0( , %) = 56) {" " % , %'( ) ≥ 1 for all ) ∈ ℕ % , %'( , ,) ≥ = J %0( , % , ,), " = 56) {" = 56) {" ≥ 56) {" = " %0( , %0( , % , ,), " " %0( , % , ,), " %0( , % , ,), " " %0( , % ) %0( , ), % ,) ∗ " %0( , % , ,), " %0( %'( , ,) % , %'( , ,), " ∗" % , %'( , ,)} Now taking ) → ∞ we obtain for all , > 0 ? ,) − − % ), ,)) J %0( ), ,), " %0( , % ) %, ), ,)} %0( %, % , %'( , ,), " % , % , ,)} %0( , % , ,) Since decreasing, then " %0( , % , ,) < " is an increasing sequence thus there ?65%→∞ " % , %'( , ,) = ? ,) < 1 ? ,) ≥ %0( ), ∗" % , %'( , ,), % , %'( , ,)} % , %'( , ,) exist % ), ,), that is {" % , %'( , ,)} ? ,) ∈ 0,1+ such that ? ,)) which is contradiction ? ,) = 1 On - - -Contraction in Fuzzy Metric Space… Thus we conclude for all , > 0 { %} ?65%→∞ " % , %'( , ,) is Cauchy sequence .since " ), ,)) = %'( , 115 =1 % → %, ) is -complete ,then % ), ), ,) J %, ) − " ≥ J Letting ) → ∞ in the above inequality using properties , Thus ?65%→∞ " Hence → % %, ?65%→∞ " )⟹ Now we assume ), ,) = 1 )= 1) − . is a fixed point of " , , ,) = " ⟹ " , , ,) = 1 ⟹ = 2.5 ), ,)) ≥ %, . ), )= such that ), ,) ≥ 1) = 0 J , ) − J , ) =0 Application On - - -Contraction Definition 2.5.22: Let , ",∗) be a fuzzy metric space and , )-admissible function, is said to be : → be an , )-contraction function of type ( I ) , if ), ), ,) ≥ J , ) . , ) , )" , )-contraction function of type (II) , if there exist 0 < ℓ ≤ 1 such that , ) , ) + ℓ)p q /),q 1),-) ≥ 1 + ℓ)r J /,1)) (a) (b) Theorem 2.5.23: Let , ",∗) be a complete fuzzy metric space and let : → be an -continuous and , )-contraction function of type (I), (II), if there exist has a unique fixed point in . K, K )) ≥ 1 and K, K )) ≥ 1 , then Proof: Let K ∈ such that Define a sequence { Since Then is %} K )) K, such that % = , )-admissible function and (, 8) = K ), () By continuing this process, we get ≥1 ≥ 1 and %0( ) K, K, K )) for all ) ∈ ℕ K )) ≥1 ≥1 116 Noori F. AL-Mayahi et al. % , %'( ) = % , %'( ) Similarly we have If = % (a) for some ) , then %'( Suppose % ≠ % , %'( ) Where J %0( , " %0( , = ≥ If 56){" = = % )) %, % ≥1 is a fixed point of . % , %'( , ,) % , %'( ) J %0( , % , %'( )" % )) = 56) {" %0( , % , ,), " % ), ,) ∗ " % , %0( ), ,)} = 56) {" = 56) {" ≥1 %'( % , %'( )" %) ≥ 56) {" % )) %, %0( , % , ,), " " %0( %0( , % , ,), " %0( , % , ,), " %0( , % , ,), " %0( ), %0( ), ,), " %0( , %0( , % , ,), " %'( , ,) ∗ " % , %'( , ,), " % , %'( , ,)} % , %'( , ,)} %, % , ,)} ∗" % ), ,), %, % , %'( , ,), " %0( , % , ,) =" % ), ,) % , %'( , ,), % , %'( , ,)} % , %'( , ,) Then " % , %'( , ,) ≥ 56){" %0( , > " % , %'( , ,) % , ,), " % , %'( , ,)}) ≥ " % , %'( , ,) Which is contradiction Therefore 56){" %0( , % , ,), " " " Hence for all ) ∈ ℕ we have % , %'( , ,) ≥ %0( , % , ,) ≥⋯≥ Let ), 5 ∈ ℕ with ) > 5 , then " % , N , ,) = %, ≥⋯≥ Therefore ?65%→∞ " %'( ) % " % , N , ,) % , %'( , ,)} ≥ % 8 " % , %'( )" K , ( , ,) =1 " =" %0( , % , ,) %08 , %0( , ,) K , ( , ,) %0( ), % ), ,) ≥ J %0( , % ) On - - -Contraction in Fuzzy Metric Space… Hence { %} 117 is a Cauchy sequence Since is an - -complete fuzzy metric space there is ∈ such that % → )→∞. ), ,) = ), ,) ≥ J % , ) " %, %, ) % , )" % ), Hence )= Suppose is a fixed point of , ) " , , ,) = = . Hence (b) , )" % , %'( ) Where J %0( , %) = 56) {" If 56){" Then " %, ), ), ,) ≥ + ℓ)p /s ,/stu ,-) p q = % , %'( ) % , %'( ) + ℓ) ≥ 1 + ℓ)r J /sUu ,/s )) %0( , % , ,), " " %0( , % , ,), " %0( , % , ,), " ≥ % , %'( , ,), " % , %'( , ,)} 56){" Therefore 56){" %0( , % , ,), " " " Hence for all ) ∈ ℕ we have ≥ =" >" %0( , % , ,) ≥⋯≥ Let ), 5 ∈ ℕ with ) > 5 , then %, % , % , ,)} % , %'( , ,)}) % , %'( , ,)} % 8 " % , %'( , ,), % , %'( , ,)} % , %'( , ,) % , %'( , ,) ≥ ∗" % ), ,), %, %0( ), ,)} % , %'( , ,), " %0( , % , ,) %0( , % , ,), " Which is contradiction % , %'( , ,) ∗" % , %'( , ,)} /sUu ),q /s ),-) %0( ), ,), " %0( , % , ,), " %0( %'( , ,) %0( , % , ,), " %'( , ,) J , )). % , %'( ) = 56) {" %0( , % , ,), " %0( , " %0( , % ), ,) ∗ " = 56) {" ≥ 56) {" )= such that " =" ≥ %0( , % , ,) %08 , %0( , ,) K , ( , ,) " % , %'( , ,) as 118 Noori F. AL-Mayahi et al. 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