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Using ψ-Operator to Formulate a New Definition of Local Function
International Journal of Mathematics and Statistics Invention (IJMSI)
1. International Journal of Mathematics and Statistics Invention (IJMSI)
E-ISSN: 2321 – 4767 || P-ISSN: 2321 - 4759
www.ijmsi.org || Volume 2 || Issue 2 || February - 2014 || PP-77-85
On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper
Bck-Algebras
1
B.Satyanarayana, 2L.Krishna and 3R.Durga Prasad
1
Department of Mathematics, Acharya Nagarjuna University,
Nagarjuna Nagar-522 510, Andhra Pradesh, India.
2
Department of Mathematics Acharya Nagarjuna University Campus Ongole
Ongole-523 002, Andhra Pradesh, India
3
Department of Science and Humanities DVR & Dr. HS, MIC College of Technology
Kanchikacherla, Andhra Pradesh, India.
ABSTRACT: In this paper, we define the notions of intuitionistic fuzzy (weak) implicative hyper BCK-ideals of
hyper BCK-algebras and then we present some theorems which characterize the above notions according to the
level subsets. Also we obtain the relationship among these notions, intuitionistic fuzzy (strong, weak, reflexive)
hyper BCK-ideals, intuitionistic fuzzy positive implicative hyper BCK-ideals of types-1, 2 ...8 and obtain some
related results.
KEY WORDS: Hyper BCK-algebras, Intuitionistic fuzzy sets, Intuitionistic fuzzy (weak) implicative hyper
BCK-ideal.
I.
INTRODUCTION:
The hyperstructure theory was introduced in 1934 by Marty [8] at the 8th congress of Scandinavian
Mathematicians. In the following years, around 40’s several authors worked on this subject, especially in
France, United States, Japan, Spain, Russia and Italy. Hyperstructers have many applications to several sectors
of both pure and applied sciences. In [7], Jun, Zahedi, Xin and Borzooei applied the Hyperstructers to BCKalgebras and introduced the notion of hyper BCK-algebras which is a generalization of a BCK-algebra. After the
introduction of the concept of fuzzy sets by Zadeh [11], several researchers were conducted on the
generalization of the notion of fuzzy sets. The idea of “Intuitionistic fuzzy set” was first published by
Atanassove [1, 2], as a generalization of the notion of fuzzy set. In [10], Jun et al. introduced the notion of
implicative hyper BCK-ideals and obtain some related results. In this paper first we define the notions of
intuitionistic fuzzy (Weak) implicative hyper BCK-ideals of hyper BCK-algebras and then we present some
theorems which characterize the above notions according to the level subsets. Also we obtain the relationship
among these notions, intuitionistic fuzzy (strong, weak, reflexive) hyper BCK-ideals, intuitionistic fuzzy
positive implicative hyper BCK-ideals of types-1, 2 ...8 and related properties are investigated.
II.
PRELIMINARIES:
Let H be a non-empty set endowed with hyper operation that is, ο is a function from
*
H H to P (H ) P (H ){ } . For any two sub-sets A and B of H, denoted by A ο B the set
a ο b. We shall use the x ο y instead of x ο {y}, {x} ο y, or {x} ο {y}.
a A, b B
Definition 2.1 [5] By a hyper BCK-algebra, we mean a non-empty set H endowed with a hyper operation " ο" and a
constant 0 satisfying the following axioms:
(HK-1) (x z) (y z) x y ,
(HK-2) (x y) z (x z) y ,
(HK-3) x H {x} ,
(HK-4) x y and y x x y for all x, y, z H.
We can define a relation “ ” on H by letting x y if and only if 0 x y and for every A ,B H ,
A B is defined by for all a A there exists b B such that a b . In such case, we call “ ” the
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2. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
hyper order in H. In the sequel H denotes hyper BCK-algebras. Note that the condition (HK3) is equivalently
to the condition : (p1) x y {x} , for all x, y H . In any hyper BCK-algebra H the following hold:
(P2) 0 0 {0} (P3) 0 x , (P4) x x , (P5) A B A B
,
(P6) 0 x {0} , (P7) x 0 {x}, (P8) 0 A {0} , (P9) x x 0 , for all x ,y ,z H for any non
empty A ,B o f H .
Let I be a non-empty subset of hyper BCK-algebra H and 0 I . Then I is called a hyper BCK-sub
algebra of H, if x y I, for all x, y I , weak hyper BCK-ideal of H if
x y I and y I x I, x ,y H , a hyper BCK-ideal of H,
if x y I and y I x I, x ,y H , a strong hyper BCK-ideal of H, if
x y I φ and y I x I, x ,y H , I is said to be reflexive if x x I x H , S-reflexive
if (x y ) I φ x y I, x ,y H , closed, if x y and y I. x I, x ,y H It is
easy to see that every S-reflexive sub-set of H is reflexive.
A hyper BCK-algebra H is called a positive implicative hyper BCK-algebra, if for all x ,y ,z H ,
(x y ) z (x z ) (y z )
Let I be a non-empty sub-set of H and 0 I . Then I is said to be a weak implicative hyper BCK-ideal
of H if (x z ) (y x ) I and z I x I an implicative hyper BCK-ideal of H, if
(x z ) (y x ) I and z I x I for all x ,y ,z X .
A fuzzy set in a set X is a function μ : X [0,1] ., and the complement of μ , denoted by μ , is the fuzzy set
in X given by μ (x) 1 μ(x) , for all x X . Let µ and λ be the fuzzy sets of X. For s, t [0,1] the set
U( μ
A
; s) {x X/ μ
A
(x) s} is called upper s- level cut of μ and the set
L( λ A ; t) {x X/ λ A (x) s} is called lower t-level cut of λ..
Let μ be a fuzzy subset of H and μ(0) μ(x) , for all x H . Then μ is called a
(i). fuzzy weak implicative hyper BCK-ideal of H if μ(x) min{
(ii) fuzzy implicative hyper BCK-ideal of H, if
μ(x) min{
μ(a),
inf
a (x z) (y x)
sup
μ(a),
μ(z)} and
μ(z)}
a (x z) (y x)
for all x, y, z H.
Definition 2.2 [1, 2] As an important generalization of the notion of fuzzy sets in X, Atanassov [1, 2] introduced
the concept of an intuitionistic fuzzy set (IFS for short) defined by “An intuitionist fuzzy set in a non-empty set
X is an object having the from A {(x, μ A (x), λ A (x))/x X} where the function μ A :X [ 0 ,1 ] and
λ A :X [ 0 ,1 ] denoted the degree of membership (namely μ
A
(x) ) and the degree of non membership
(namely λ A (x)) of each element x X to the set A respectively and 0 μ A (x) λ A (x) 1 , x X .
For the sake of simplicity, we use the symbol form A (X, μ A , λ A ) or A ( μ A , λ A ) ”.
Definition 2.3 [4] An IFS A (μ A , λ A ) in H is called an intuitionistic fuzzy hyper BCK-ideal of H if it
satisfies
(k1)
x y μ A (x ) μ A (y )
(k2)
μ
(k3)
λ
A
A
and λ A (x) λ A (y) ,
(a) , μ
(y)} ,
(x)
min{ inf μ A
a x y
(x)
max{
sup λ
A
(b) , μ
(y)}
A
A
b x y
for all x, y H .
Definition 2.4 [4] An IFS A (μ A , λ A ) in H is called an intuitionistic fuzzy strong hyper BCK-ideal
of H if it satisfies
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3. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
μ (a) μ (x) min{ sup μ A (b) , μ (y)} and
inf
A
A
A
a x x
b x y
(sh1)
(sh2)
λ
sup
c x x
A
(c) λ
A
(x) max{ inf λ A (d) , λ (y)} x ,y H .
A
d x y
Definition 2.5 [4] An IFS A (μ A , λ A ) in H is called an intuitionistic fuzzy s-weak hyper BCK-ideal
of H if it satisfies
(y) and λ (0) λ (y) , for all x, y H .
A
A
A
(s2) for every x, y H there exists a ,b x y , μ (x) min{ μ (a), μ (y)} and
A
A
A
λ (x) max{ λ (b), λ (y)} .
A
A
A
(s1) μ
A
(0) μ
Definition 2.6 [4] An IFS A (μ A , λ A ) in H is called an intuitionistic fuzzy weak hyper BCK-ideal of H if it
satisfies
μ (0) μ (x) min{ inf μ A (a) , μ (y)} and
A
λ
A
A
(0) λ
A
A
a x y
(x) max{ sup λ A (b) , λ (y)} x ,y H .
A
b x y
Definition 2.7 [4] An IFS A (μ A , λ A ) in H is said to satisfy the “sup-inf” property if for any sub-set T of H
there exist x 0 , y 0 T such that μ
A
(x
0
) sup μ
xT
A
(x) and λ
A
(y
0
) inf μ (y) .
A
y T
Definition 2.8 [9] Let A ( μ A , λ A ) be an intuitionistic fuzzy sub-set of H and μ A (0) μ A (x) ,
λ A (0) λ A (y) for all x ,y H . Then A ( μ
A
, λ A ) is said to be an intuitionistic fuzzy positive
implicative hyper BCK-ideal of
(i)
type 1, if for all t x z ,
μ
λ
(ii)
A
A
λ
A
A
(t) max{
λ
sup
c (x y) z
A
(c),
sup
λ
d y z
A
(d)} .
(t) min{
sup
μ
a (x y) z
(t) max{
A
(a),
μ (b)} and
inf
A
b y z
λ (c), sup λ (d)}
inf
A
A
c (x y) z
d y z
type 3, if for all t x z ,
μ
λ
(iv)
μ (a), inf
μ (b)} and
inf
A
A
a (x y) z
b y z
type 2, if for all t x z ,
μ
(iii)
(t) min{
A
A
(t) min{
sup
μ
a (x y) z
(t) max{
A
(a),
sup
μ
b y z
A
(b)} and
λ (c), inf
λ (d)} .
inf
A
A
c (x y) z
d y z
type 4, if for all t x z ,
μ
λ
A
A
(t) min{
(t) max{
μ (a), sup μ (b)} and
inf
A
A
a (x y) z
b y z
λ
sup
c (x y) z
A
(c),
λ (d)} x ,y , z H
inf
A
d y z
Definition 2.9[9] Let A ( μ A , λ A ) be an intuitionistic fuzzy sub-set of H. Then A ( μ A , λ A ) is said to
be an intuitionistic fuzzy positive implicative hyper BCK-ideal of
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4. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
type 5, if there exists t x z such that
(i)
μ
λ
A
(t) min{
μ (a), inf
μ (b)} and
inf
A
A
a (x y) z
b y z
(t) max{
λ
sup
c (x y) z
A
(c),
λ
sup
d y z
A
(d)} .
type 6, if there exists t x z such that
(ii)
μ
λ
A
A
(t) min{
μ
sup
a (x y) z
(t) max{
A
(a),
μ
sup
b y z
A
(b)} and
λ (c), inf
λ (d)} .
inf
A
A
c (x y) z
d y z
type 7, if there exists t x z such that
(iii)
μ
λ
A
A
(t) min{
μ (a), sup μ (b)} and
inf
A
A
a (x y) z
b y z
(t) max{
λ
sup
c (x y) z
A
(c),
λ (d)} .
inf
A
d y z
(a),
μ (b)} and
inf
A
b y z
type 8, if there exists t x z such that
(iv)
μ
λ
III.
A
A
A
(t) min{
μ
sup
a (x y) z
(t) max{
A
λ (c), sup λ (d)} .
inf
A
A
c (x y) z
d y z
INTUITIONISTIC FUZZY IMPLICATIVE HYPER BCK-IDEALS OF HYPER BCKALGEBRAS
Definition 3.1 Let A ( μ A , λ A ) be an intuitionistic fuzzy set on H and μ A (0) μ A (x) , λ A (0) λ A (y)
x ,y H . Then A ( μ A , λ A ) is called an
(i) intuitionistic fuzzy weak implicative hyper BCK-ideal of H if
μ
λ
A
A
(x) min{
(x) max{
μ (a), μ (z)} and
inf
A
A
a (x z) (y x)
λ
sup
b (x z) (y x)
A
(b), λ
A
(z)} .
(ii) intuitionistic fuzzy implicative hyper BCK-ideal of H, if
μ
λ
A
A
(x) min{
μ
sup
a (x z) (y x)
(x) max{
A
(a), μ
A
(z)} and
λ (b), λ (z)} for all x, y, z H.
inf
A
A
b (x z) (y x)
Theorem 3.2 Every intuitionistic fuzzy implicative hyper BCK-ideal of H is an intuitionistic fuzzy weak
implicative hyper BCK-ideal.
Proof: Suppose A ( μ A , λ A ) is an intuitionistic fuzzy implicative hyper BCK-ideal of H and for
x, y, z H. we have
(a)
sup μ (a)
and
A
A
a (x z) (y x)
a (x z) (y x)
inf μ
(b)
sup λ (b)
.
A
A
b (x z) (y x)
b (x z) (y x)
inf λ
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5. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
Therefore
μ
λ
A
A
(x) min{
μ
sup
a (x z) (y x)
(x) max{
A
(a), μ
A
(z)} min{
μ (a), μ (z)} and
inf
A
A
a (x z) (y x)
λ (b), λ (z)} max{
λ (b), λ (z)} .
sup
inf
A
A
A
A
b (x z) (y x)
b (x z) (y x)
Thus A ( μ A , λ A ) is an intuitionistic fuzzy weak implicative hyper BCK-ideal of H.
Example 3.3 Let H {0, a, b} . Consider the following cayley table
º
0
a
b
0
{0}
{0}
{0}
a
{a}
{0, a}
{0, a}
b
{b}
{a}
{0, a}
Then (H, ) is a hyper BCK-algebra [5].
Define an IFS A (μ A , λ A ) on H by μ A (0) 1 , μ A (a) 0, μ A (b) 0.6
and λ A (0) 0 , λ A (a) 1, and λ A (b) 0.4 . Then A (μ A , λ A ) is an intuitionistic fuzzy weak
implicative hyper BCK-ideal of H but it is not an intuitionistic fuzzy implicative hyper BCK-ideal of H, because
μ (a) 0 1 μ (0) min{
μ (t), μ (0)} and
sup
A
λ
A
A
(a) 1 0 λ
A
t (a 0) (a a)
(0) max{
A
A
λ (t), λ (0)} .
inf
A
A
t (a 0) (a a)
Theorem 3.4
(1). Every intuitionistic fuzzy implicative hyper BCK-ideal of H is an intuitionistic fuzzy strong hyper BCK-ideal.
(2). Every intuitionistic fuzzy weak implicative hyper BCK-ideal of H is an intuitionistic fuzzy weak hyper BCK-ideal.
Proof: (i) Let A (μ A , λ A ) be an intuitionistic fuzzy implicative hyper BCK-ideal of H.
By putting y 0 and z y in Definition 3.1(ii), we get
μ
λ
A
A
(x) min{
μ
(a),
μ
λ (b),
inf
A
b (x y) (0 x)
λ
sup
A
a (x y) (0 x)
(x) max{
A
A
(y)} min{ sup μ A (a) , μ
(y)} and
A
a x y
(y)} max{
(b) , λ (y)} ….. (i).
A
A
b x y
λ
inf
(x) μ (y) and λ (x) λ (y)
A
A
A
A
For this, let x, y H be such that x y , then 0 x y and so from (i), we get
First we show that, for x, y H , if x y implies μ
μ
λ
A
A
(x) min{
(a),
μ
λ (b),
inf
A
b x y
λ
sup
μ
a x y
(x) max{
A
A
A
(y)} min{
(y)} max{
μ
A
λ
(0) , μ
A
A
(0) , λ
(y)} μ
A
A
(y)} λ
(y) and
A
(y) …..(ii).
L e t x H and a x x . Since x x x then a x for all a x x and so by (ii), we have
μ
A
(a) μ
Hence
A
(x) and λ
A
(a) λ
A
(x) for all a x x .
μ (a) μ
(x) and
λ (a) λ (x).....(i ii) .
sup
inf
A
A
A
A
a x x
a x x
Combining (i) and (iii), we get
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6. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
μ
(a) μ
(x) min{ sup μ A (b) , μ
(y)} and
inf
A
A
A
a x x
b x y
λ
sup
c x x
A
(c) λ
(d) , λ (y)} for all x, y H.
A
A
d x y
(x) max{
A
λ
inf
Thus A (μ A , λ A ) is an intuitionistic fuzzy strong hyper BCK-ideal of H.
(ii) Let A (μ A , λ A ) be an intuitionistic fuzzy weak implicative hyper BCK-ideal of H.
By putting y 0 and z y in Definition 3.1(i), we get
μ
λ
A
A
(x) min{
μ
(a),
inf
A
a (x y) (0 x)
(x) max{
λ
sup
b (x y) (0 x)
Therefore, μ
λ
A
A
(0) μ
(0) λ
A
A
A
μ
A
λ
(b),
A
(y)} min{ inf μ A (a) , μ
(y)} and
A
a x y
(y)} max{
λ
(b) , λ (y)} .
A
A
b x y
sup
(x) min{ inf μ A (a) , μ
(y)} and
A
a x y
(x) max{
(b) , λ (y)} for all x, y H.
A
A
b x y
λ
sup
Thus A (μ A , λ A ) is an intuitionistic fuzzy weak implicative hyper BCK-ideal of H.
Example 3.5 Let H {0, a, b, c} . Consider the following cayley table:
0
a
b
c
0
{0}
{0}
{0}
{0}
a
{a}
{0}
{0}
{0}
b
{b}
{b}
{0}
{0}
c
{c}
{c}
{b, c}
{0, b, c}
Then (H, ) is a hyper BCK-algebra [5].
Define IFS A (μ A , λ A ) in H by μ A (0) μ A (a) 1, μ A (b) μ A (c) 0.4 and
λ A ( 0 ) λ A ( a ) 0 , λ A ( b ) λ A ( c ) 0 .5 .
Then A (μ A , λ A ) is an intuitionistic fuzzy strong hyper BCK-ideal (and so is an intuitionistic
fuzzy weak hyper BCK-ideal) but it is not an intuitionistic fuzzy implicative (and so is not an
intuitionistic fuzzy weak implicative) hyper BCK-ideal of H. Because
μ (b) 0.4 1 μ (0) min{
μ (t), μ (0)} and
inf
A
λ
A
A
(b ) 0 .5 0 λ
A
A
t (b 0) (c b)
(0 ) m a x {
sup
t (b 0 ) (c b )
λ
A
(t), λ
A
A
(0 )}
This implies that the converse of the Theorem 3.4 is not correct in general.
Theorem 3.6 Let A (μ A , λ A ) be an intuitionistic fuzzy sub-set of H, then the following statements hold:
(i). A is an intuitionistic fuzzy weak implicative hyper BCK-ideal of H if and only if for all s ,t [0 ,1 ],
U ( μ A ;s ) L ( λ A ;t) are weak implicative hyper BCK- ideals of H.
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7. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
(ii). if A is an intuitionistic fuzzy implicative hyper BCK-ideal of H, then for all s ,t [0 ,1 ],
U ( μ A ;s ) L ( λ A ;t) are implicative hyper BCK- ideals of H.
(iii). If for all s ,t [ 0 ,1 ] , U ( μ A ;s ) L ( λ A ;t) are S-reflexive implicative hyper BCK- ideals of H, and
A satisfies the “sup-inf” property, then A is an intuitionistic fuzzy implicative hyper BCK-ideal of H.
Proof: (i) Assume A (μ A , λ A ) is an intuitionistic fuzzy weak implicative hyper BCK-ideal of H.
Let s, t [0,1] and x, y, z X be such that (x z) (y x) U( μ A ; s) and z U( μ A ; s) .
Then a U( μ A ; s) for all a (x z) (y x) implies μ A (a) s, for all a (x z) (y x) and
μ A (z) s , implies that
(a)
s and μ A (z) s . Thus by hypothesis,
A
a (x z) (y x)
inf μ
in f μ A (a )
μ A (x ) m in
a (x z ) (y x )
μ A (z )
m in { s ,s } s .
Imply x U( μ A ; s) . Let x, y, z X be such that (x z) (y x) L( λ A ; t) and z L( λ A ; t) . Then
b L( λ A ; t), for all b (x z) (y x) . Implies λ A (c) t , for all c (x z) (y x) and λ A (z) t,
implies that
λ
A
sup λ
(b)
A
b (x z) (y x)
(x) max{
t and λ A (z) t . Thus by hypothesis,
λ
sup
b (x z) (y x)
A
(b), λ
A
(z)} max{t, t} t x L (λ A ;t) .
Therefore U( μ A ; s) and L( λ A ; t) are weak implicative hyper BCK-ideals of H, for all s, t [0,1] .
Conversely let for all s, t 0,1 , U( μ A ; t) φ L( λ A ; s) are weak implicative hyper BCK-ideals of H and
inf μ
let x, y, z H and put s min
A
(a)
,
μ
A
a (x z) ( y x )
μ
A
(z) s . So that μ
A
(z)
inf μ A (a)
s and
. Then
a (x z) (y x)
(a) s for all a (x z) (y x) and μ
A
(z) s .
Hence a U( μ A ; s) for all a (x z) (y x) and z U( μ A ; s) . That is,
(x z) (y x) U( μ
A
; s) , z U( μ
A
; s) and so by hypothesis
,
in f μ A (a )
x U( μ A ; s) m in
a (x z ) (y x )
in f μ A (a )
μ A (z )
.
,
Thus μ A (x ) s m in
a (x z ) (y x )
Let x ,y ,z H and put t max{
μ A (z )
.
λ
sup
b (x z) (y x)
A
(b), λ
A
(z)}
t
sup
λ A (b )
b (x z ) (y x )
and
λ A (z) t so that λ A (b) t for all b (x z) (y x) and λ A (z) t implies b L( λ A ; t) for all
b (x z) (y x) and z L( λ A ; t) . Hence (x z) (y x) L( λ A ; t) and z L( λ A ; t) . By
hypothesis x L( λ A ; t) . Thus λ
A
(x) t max{
sup
b (x z) (y x)
λ
A
(b), λ
A
(z)} .
Therefore A (μ A , λ A ) is an intuitionistic fuzzy weak implicative hyper BCK-ideal of H.
(ii) Suppose A (μ A , λ A ) is an intuitionistic fuzzy implicative hyper BCK-ideal of H.
By Theorem 3.4(i), A (μ A , λ A ) is an intuitionistic fuzzy strong hyper BCK-ideal of H and so it is an
intuitionistic fuzzy hyper BCK-ideal of H by Theorem 3.17 [4], for all s, t [0,1]
,
U( μ A ; s) φ L( λ A ; t) are hyper BCK-ideals of H. By Theorem 4.6(ii) [5], it is enough to show that, let
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8. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
if x ( y x ) U( μ A ; s) and x (y x) L( λ A ; t) , then x U( μ A ; s) L( λ A ; t) .
x, y, z H and
For this, let x ( y x ) U( μ A ; s) for x, y H. Then for all a x ( y x) there exists b U( μ A ; s)
such that a b , we have μ A (a) μ A (b) s implies μ A (a) s for
all a x ( y x) implies
sup μ
A
(a)
s.
a x (y x)
Hence by hypothesis,
μ
A
(x) min{
μ
sup
a (x 0) (y x)
A
μ
(a),
A
(0)} sup μ A (a) s
a x (y x)
That is x U( μ A ; s) . Let x (y x) L( λ A ; t) for x, y H. Then for all c x ( y x) there exists
d L( λ A ; t) such that c d . We have λ A (c) λ A (d) t implies λ A (c) t for all c x ( y x)
implies
inf λ A (c)
c x (y x)
λ
A
t . Hence by hypothesis,
(x) max{
λ (a),
inf
A
c (x 0) (y x)
λ
A
(0)} inf λ A (c) t .
c x (y x)
That is, x L( λ A ; t) . Thus U( μ A ; s) and L( λ A ; t) are implicative hyper BCK-ideals of H, for
all s, t 0,1 .
(iii) Assume that, for all s, t 0,1 , U( μ A ; s) and L( λ A ; t) are S-reflexive implicative hyper BCK-ideal of
H. Let x, y, z H.
Put s min{
μ
sup
a (x z) (y x)
μ
A
(z) s , Since μ
μ
A
(a
0
)
A
sup μ
A
(a), μ
A
(z)} imply
(a)
s and
A
a (x z) (y x)
sup μ
satisfies the “sup” property, then there exists a 0 (x z) (y x) such that
A
(a)
a (x z) ( y x )
((x (y x)) z) U( μ
A
s and so a
0
U( μ
A
; s) , hence by (HK2), we have
; s) ((x z) (y x)) U( μ
a (x (y x)) such that (a z) U( μ
A
A
; s) φ , then there exists
; s) φ . Since by Theorem 4.6(i)[5], U( μ
A
; s) is a hyper
BCK-ideal of H and hypothesis U( μ A ; s) is S-reflexive, then it is reflexive hyper BCK-ideal of H, by Theorem
2.3(i) [5] and so it is strong hyper BCK-ideal of H. Since μ A ( z ) s z U( μ A ; s) ,
(a z) U( μ
A
; s) φ and z U( μ
A
; s) , then a U( μ
A
; s) and so ( x ( y x ) ) U ( μ A ;s ) φ .
Since U( μ A ; s) is reflexive, by Theorem 3.5(ii)[5], x (y x) U( μ A ; s) , U( μ A ; s) is an implicative
hyper BCK-ideal of H then x U( μ A ; s) and so
μ
A
(x) s min{
sup
μ
a (x z) (y x)
A
(a), μ
A
(z)} .
Since L( λ A ; t) is S-reflexive implicative hyper BCK-ideal of H and x, y, z H.
Put t max{
inf λ (a)
t and λ A (z) t
λ (a), λ (z)} implies
inf
A
A
A
a (x z) (y x)
a (x z) (y x)
Since λ A satisfies the “inf” property, then there exist b 0 (x z) (y x) such that
λ
A
(b
0
)
inf λ
A
(a)
a (x z) (y x)
t and so b 0 L( λ A ; t) , hence by (HK2), we have
(x (y x)) z) L( λ A ; t) ((x z) (y x)) L( λ A ; t) φ , then there exist b (x (y x)) such
that (b z) L( λ A ; t) φ . Since by the theorem 4.6(i)[5], L( λ A ; t) is a hyper BCK-ideal of H and
hypothesis L( λ A ; t) is S-reflexive, then it is reflexive hyper BCK-ideal of H, by Theorem 2.3(i) [5] and so it is
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9. On Intuitionistic Fuzzy Implicative Hyper Bck-Ideals of Hyper Bck-Algebras
strong hyper BCK-ideal of H. Since λ A ( z ) t z L( λ A ; t) , (b z) L( λ A ; t) φ and z L( λ A ; t)
then b L( λ A ; t) and so (x (y x)) L( λ A ; t) φ . L( λ A ; t) is reflexive, by Theorem 3.5(ii)[5] then
x (y x) L( λ A ; t) , L( λ A ; t) is a implicative hyper BCK-ideal of H, by theorem 4.6(ii)[5], we have
x L( λ A ; t) and so λ
A
(x) t max{
λ (a), λ (z)}
inf
A
A
a (x z) (y x)
Therefore A (μ A , λ A ) is an intuitionistic fuzzy implicative hyper BCK-ideal of H.
Theorem 3.7 Let A (μ A , λ A ) be an intuitionistic fuzzy set on H.
(i). If A satisfies the “sup-inf” property and for all s, t [0,1] , U( μ A ; s) and L( λ A ; t) are reflexive and A is
an intuitionistic fuzzy implicative hyper BCK-ideal of H, then A is an intuitionistic fuzzy positive implicative
hyper BCK-ideal of type 3.
(ii). Let H be a positive implicative hyper BCK-algebra. If A (μ A , λ A ) is an intuitionistic fuzzy weak
implicative hyper BCK-ideal of H, then A is an intuitionistic fuzzy positive implicative hyper BCK-ideal of type
1
Theorem 3.8 Let A (μ A , λ A ) be an IFS on H. Then A is an intuitionistic fuzzy weak implicative hyper
BCK-ideal if and only if the fuzzy sets μ
A
and λ A are fuzzy weak implicative hyper BCK-ideals of H.
Theorem 3.9 Let A (μ A , λ A ) be an IFS on H. Then A is an intuitionistic fuzzy weak implicative hyper
BCK-ideal if and only if the fuzzy sets A ( μ A , μ A ) and A ( λ A , λ A ) are intuitionistic fuzzy weak
implicative hyper BCK-ideals of H.
Proof: The proof follows from the Theorem 3.8
Theorem 3.10 Let A (μ A , λ A ) be an IFS on H. Then A is an intuitionistic fuzzy implicative hyper BCKideal if and only if the fuzzy sets μ
A
and λ A are fuzzy implicative hyper BCK-ideals.
Theorem 3.11 Let A (μ A , λ A ) be an IFS on H. Then A is an intuitionistic fuzzy implicative hyper BCKideal if and only if the A ( μ A , μ A ) and A ( λ A , λ A ) are fuzzy implicative hyper BCK-ideals.
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