Hindawi Publishing Corporation The Scientific World Journal Volume 2013, Article ID 365065, 8 pages http://dx.doi.org/10.1155/2013/365065
Research Article Generalized Bifuzzy Lie Subalgebras Noura Alshehri1 and Muhammad Akram2 1 2
Department of Mathematics, Faculty of Sciences (Girls), King Abdulaziz University, Jeddah, Saudi Arabia Punjab University College of Information Technology, University of the Punjab, Old Campus, Lahore, Pakistan
Correspondence should be addressed to Muhammad Akram;
[email protected] Received 1 September 2013; Accepted 21 November 2013 Academic Editors: F. Feng and N. Kamide Copyright Β© 2013 N. Alshehri and M. Akram. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We introduce the concept of (πΎ, πΏ)-bifuzzy Lie subalgebra, where πΎ, πΏ are any two of {β, π, β β¨π, β β§π} with πΎ =ΜΈ β β§π, by using belongs to relation (β) and quasi-coincidence with relation (π) between bifuzzy points and bifuzzy sets and discuss some of its properties. Then we introduce bifuzzy soft Lie subalgebras and investigate some of their properties.
1. Introduction The concept of Lie groups was first introduced by Sophus Lie in nineteenth century through his studies in geometry and integration methods for differential equations. Lie algebras were also discovered by him when he attempted to classify certain smooth subgroups of a general linear group. The importance of Lie algebras in mathematics and physics has become increasingly evident in recent years. In applied mathematics, Lie theory remains a powerful tool for studying differential equations, special functions, and perturbation theory. It is noted that Lie theory has applications not only in mathematics and physics but also in diverse fields such as continuum mechanics, cosmology, and life sciences. A Lie algebra has nowadays even been applied by electrical engineers in solving problems in mobile robot control [1]. After introducing the concept of fuzzy sets by Zadeh [2] in 1965, there are many generalizations of this fundamental concept. Among these new concepts, the concept of intuitionistic fuzzy sets given by Atanassov [3] in 1983 is the most important and interesting one because it is simply an extension of fuzzy sets. In 1995, Gerstenkorn and MaΒ΄nko [4] renamed the intuitionistic fuzzy sets as bifuzzy sets. The elements of the bifuzzy sets are featured by an additional degree which is called the degree of uncertainty. This kind of fuzzy sets have now gained a wide recognition as a useful tool in the modeling of some uncertain phenomena. Bifuzzy sets have drawn the attention of many researchers in the last
decades. This is mainly due to the fact that bifuzzy sets are consistent with human behavior, by reflecting and modeling the hesitancy present in real-life situations. In fact, the fuzzy sets give the degree of membership of an element in a given set, while bifuzzy sets give both a degree of membership and a degree of nonmembership. As for fuzzy sets, the degree of membership is a real number between 0 and 1. This is also the case for the degree of nonmembership, and furthermore the sum of these two degrees is not greater than 1. In 1999, Molodtsov [5] initiated the novel concept of soft set theory to deal with uncertainties which can not be handled by traditional mathematical tools. He successfully applied the soft set theory several disciplines, such as game theory, Riemann integration, Perron integration, and measure theory. Applications of soft set theory in real life problems are now catching momentum due to the general nature parametrization expressed by a soft set. Maji et al. [6] gave first practical application of soft sets in decision making problems. They also presented the definition of intuitionistic fuzzy soft set [7]. Yehia introduced the notion of fuzzy Lie subalgebras of Lie algebras in [8] and studied some results. Akram and Feng introduced the notion of soft Lie subalgebras of Lie algebras in [9] and studied some of their results. Akram et al. introduced the notions of fuzzy soft Lie subalgebras in [10]. In this paper, we introduce a new kind of generalized bifuzzy Lie algebra, an (πΎ, πΏ)-bifuzzy Lie algebra, and discuss some of its properties. Then we introduce bifuzzy soft Lie
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algebras and investigate some of their properties. We use standard definitions and terminologies in this paper.
2. Preliminaries In this section, we review some known basic concepts that are necessary for this paper. A Lie algebra is a vector space πΏ over a field πΉ (equal to R or C) on which πΏ Γ πΏ β πΏ denoted by (π₯, π¦) β [π₯, π¦] is defined satisfying the following axioms: (L1) [π₯, π¦] is bilinear, (L3) [[π₯, π¦], π§]+[[π¦, π§], π₯]+[[π§, π₯], π¦] = 0 for all π₯, π¦, π§ β πΏ (Jacobi identity). Throughout this paper, πΏ is a Lie algebra and πΉ is a field. We note that the multiplication in a Lie algebra is not associative; that is, it is not true in general that [[π₯, π¦], π§] = [π₯, [π¦, π§]]. But it is anticommutative; that is, [π₯, π¦] = β[π¦, π₯]. A subspace π» of πΏ closed under [β
, β
] will be called a Lie subalgebra. Let π be a fuzzy set on π; that is, a map π : π β [0, 1]. As an important generalization of the notion of fuzzy sets in π, Atanassov introduced the concept of a bifuzzy set defined on a nonempty set π as objects having the form (1)
where the functions π : π β [0, 1] and ] : π β [0, 1] denote the degree of membership (viz., ππ΄ (π₯)) and the degree of nonmembership (viz., ]π΄(π₯)) of each element π₯ β π to the set π΄, respectively, and 0 β€ ππ΄ (π₯) + ]π΄(π₯) β€ 1 for all π₯ β π. Definition 1 (see [3, 11]). Let π΄ = (ππ΄ , ]π΄) be a bifuzzy set on π and let π , π‘ β [0, 1] be such that π + π‘ β€ 1. Then the set π΄ (π ,π‘) = {π₯ | ππ΄ (π₯) β₯ π , ]π΄ (π₯) β€ π‘}
Definition 4. Let π and π be any two bifuzzy subsets of πΏ. Then the sum π + π is a bifuzzy subset of πΏ defined by (ππ + ππ ) (π§)
(L2) [π₯, π₯] = 0 for all π₯ β πΏ,
π΄ = (ππ΄ , ]π΄) = {(π₯, ππ΄ (π₯) , ]π΄ (π₯)) | π₯ β π} ,
BP in π and let π΄ = β¨π₯, ππ΄ , ]π΄β© be a bifuzzy set in π. Then π(πΎ, πΏ) is said to belong to π΄, written π(πΎ, πΏ) β π΄, if ππ΄ (π) β₯ πΎ and ]π΄(π) β€ πΏ. We say that π(πΎ, πΏ) is quasicoincident with π΄, written π(πΎ, πΏ)ππ΄, if ππ΄(π)+πΎ > 1 and ]π΄(π)+πΏ < 1. To say that π(πΎ, πΏ) β β¨ππ΄ (resp., π(πΎ, πΏ) β β§ππ΄) means that π(πΎ, πΏ) β π΄ or π(πΎ, πΏ)ππ΄ (resp., π(πΎ, πΏ) β π΄ and π(πΎ, πΏ)ππ΄) and π(πΎ, πΏ)β β¨ππ΄ means that π(πΎ, πΏ) β β¨ππ΄ does not hold.
(2)
is called an (π , π‘)-level subset of π΄. π΄ (π ,π‘) is a crisp set. Definition 2 (see [12]). A bifuzzy set π΄ = (ππ΄ , ]π΄) on πΏ is called a bifuzzy Lie subalgebra if the following conditions are satisfied: (i) ππ΄ (π₯ + π¦) β₯ min{ππ΄ (π₯), ππ΄ (π¦)}, (ii) ]π΄(π₯ + π¦) β€ max{]π΄(π₯), ]π΄(π¦)}, (iii) ππ΄ (πΌπ₯) β₯ ππ΄ (π₯), ]π΄(πΌπ₯) β€ ]π΄(π₯), (iv) π([π₯, π¦]) β₯ max{π(π₯), π(π¦)}, (v) ]([π₯, π¦]) β€ min{](π₯), ](π¦)} for all π₯, π¦ β πΏ and πΌ β πΉ. Definition 3 (see [13]). Let π be a point in a nonempty set π. If πΎ β (0, 1] and πΏ β [0, 1) are two real numbers such that 0 β€ πΎ + πΏ β€ 1, then the bifuzzy set π(πΎ, πΏ) = β¨π₯, ππΎ , 1 β π1βπΏ β© is called a bifuzzy point (BP for short) in π, where πΎ (resp., πΏ) is the degree of membership (resp., nonmembership) of π(πΎ, πΏ) and π β π is the support of π(πΎ, πΏ). Let π(πΎ, πΏ) be a
{ β (ππ (π) β§ ππ (π) β§ ππ (π) β§ ππ (π)) = {π§=[π₯,π¦] {0
for π§ = [π₯, π¦] , otherwise,
(]π + ]π ) (π§) { β (]π (π) β¨ ]π (π) β¨ ]π (π) β¨ ]π (π)) = {π§=[π₯,π¦] {1
for π§ = [π₯, π¦] , otherwise.
(3)
Let IF(π) denote the family of all bifuzzy sets in π. Definition 5 (see [7]). Let π be an initial universe and π΄ β πΈ a set of parameters. A pair (π, π΄) is called a bifuzzy soft set over π, where π is a mapping given by π : π΄ β πΌπΉ(π). A bifuzzy soft set is a parameterized family of bifuzzy subsets of π. For any π β π΄, ππ is referred to as the set of π-approximate elements of the bifuzzy soft set (π, π΄), which is actually a bifuzzy set on π and can be ππ = {(πππ (π₯) , ]ππ (π₯)) | π₯ β π} ,
(4)
where πππ (π₯) and ]ππ (π₯) are the membership degree and nonmembership degree that object π₯ holds on parameter π, respectively. Definition 6 (see [7]). Let (π, π΄) and (π, π΅) be two bifuzzy soft sets over π. We say that (π, π΄) is a bifuzzy soft subset of (π, π΅) and write (π, π΄) β (π, π΅) if (i) π΄ β π΅, (ii) for any π β π΄, π(π) β π(π). (π, π΄) and (π, π΅) are said to be bifuzzy soft equal and write (π, π΄) = (π, π΅) if (π, π΄) β (π, π΅) and (π, π΅) β (π, π΄). Definition 7 (see [7, 14]). Let (π, π΄) and (π, π΅) be two bifuzzy soft sets over π. Then their extended intersection is a bifuzzy soft set denoted by (β, πΆ), where πΆ = π΄ βͺ π΅ and π { { π β (π) = {ππ { {ππ β© ππ
if π β π΄ β π΅, if π β π΅ β π΄, if π β π΄ β© π΅,
(5)
Μ (π, π΅). for all π β πΆ. This is denoted by (β, πΆ) = (π, π΄) β© Definition 8 (see [7, 14]). If (π, π΄) and (π, π΅) are two bifuzzy soft sets over the same universe π then β(π, π΄) AND (π, π΅)β
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is a bifuzzy soft set denoted by (π, π΄) β§ (π, π΅) and is defined by (π, π΄) β§ (π, π΅) = (β, π΄ Γ π΅), where, β(π, π) = β(π) β© π(π) for all (π, π) β π΄ Γ π΅. Here β© is the operation of a bifuzzy intersection. Definition 9 (see [7, 14]). Let (π, π΄) and (π, π΅) be two bifuzzy soft sets over π. Then their extended union is denoted by (β, πΆ), where πΆ = π΄ βͺ π΅ and ππ { { { { β (π) = {ππ { { { {ππ βͺ ππ
if π β π΄ β π΅, if π β π΅ β π΄,
(6)
if π β π΄ β© π΅,
Μ (π, π΅). for all π β πΆ. This is denoted by (β, πΆ) = (π, π΄) βͺ Definition 10 (see [7, 14]). Let (π, π΄) and (π, π΅) be two fuzzy soft sets over a common universe π with π΄β©π΅ =ΜΈ 0. Then their restricted intersection is a bifuzzy soft set (β, π΄ β© π΅) denoted by (π, π΄) β (π, π΅) = (β, π΄ β© π΅), where β(π) = π(π) β© π(π) for all π β π΄ β© π΅. Definition 11 (see [7, 14]). Let (π, π΄) and (π, π΅) be two bifuzzy soft sets over a common universe π with π΄β©π΅ =ΜΈ 0. Then their restricted union is denoted by (π, π΄) β (π, π΅) and is defined as (π, π΄) β (π, π΅) = (β, πΆ), where πΆ = π΄ β© π΅ and for all π β πΆ, β(π) = π(π) βͺ π(π). Definition 12 (see [7, 14]). The extended product of two bifuzzy soft sets (π, π΄) and (π, π΅) over π is a fuzzy soft set, denoted by (π β π, πΆ), where πΆ = π΄ βͺ π΅, and defined by π (π) { { { { (π β π) (π) = {π (π) { { { {π (π) β π (π)
if π β π΄ β π΅, if π β π΅ β π΄,
(7)
if π β π΄ β© π΅,
for all π β πΆ. This is denoted by (π β π, πΆ) = (π, π΄) Μβ (π, π΅).
3. Bifuzzy Lie Algebras In this section, we introduce a new kind of generalized bifuzzy Lie algebra, an (πΎ, πΏ)-bifuzzy Lie subalgebra, and discuss some of its properties. Definition 13. A bifuzzy set π΄ = (ππ΄ , ]π΄) in πΏ is called an (πΎ, πΏ)-bifuzzy Lie subalgebra of πΏ if it satisfies the following conditions: (a) π₯(π 1 , π‘1 )πΎπ΄, π¦(π 2 , π‘2 )πΎπ΄ β (π₯+π¦)(min(π 1 , π 2 ), max(π‘1 , π‘2 ))πΏπ΄, (b) π₯(π , π‘)πΎπ΄ β (ππ₯)(π , π‘)πΏπ΄, (c) π₯(π 1 , π‘1 )πΎπ΄, π¦(π 2 , π‘2 )πΎπ΄ β [π₯, π¦](max(π 1 , π 2 ), min(π‘1 , π‘2 ))πΏπ΄ for all π₯, π¦ β πΏ, π β πΉ, π , π 1 , π 2 β (0, 1], π‘, π‘1 , π‘2 β [0, 1). Remark 14. Consider (i) π₯(π , π‘)πΎπ΄ β (βπ₯)(π , π‘)πΏπ΄, (ii) π₯(π , π‘)πΎπ΄ β (0)(π , π‘)πΏπ΄.
Example 15. Let π be a vector space over a field πΉ such that dim(π) = 5. Let π = {π1 , π2 , . . . , π5 } be a basis of a vector space over a field πΉ with Lie brackets as follows: [π1 , π2 ] = π3 ,
[π1 , π3 ] = π5 ,
[π1 , π4 ] = π5 ,
[π1 , π5 ] = 0,
[π2 , π3 ] = π5 , [π2 , π5 ] = 0, [π3 , π5 ] = 0,
[π4 , π5 ] = 0,
[π2 , π4 ] = 0,
(8)
[π3 , π4 ] = 0, [ππ , ππ ] = β [ππ , ππ ]
and [ππ , ππ ] = 0 for all π = π. Then π is a Lie algebra over πΉ. We define a bifuzzy set π΄ = (ππ΄ , ]π΄) : π β [0, 1] Γ [0, 1] by 1 ππ΄ (π₯) := { 0.5
if π₯ = 0, otherwise,
0 ]π΄ (π₯) := { 0.3
if π₯ = 0, otherwise.
(9)
Take π = 0.4 β (0, 1] and π‘ = 0.5 β [1, 0). By routine computations, it is easy to see that π΄ is not an (πΎ, πΏ)-bifuzzy Lie subalgebra of πΏ. For a bifuzzy set π΄ in πΏ, we denote πΏ(0, 1) = {π₯ β πΏ : π(π₯) > 0 and ](π₯) < 1}. Theorem 16. Let π΄ = (ππ΄ , ]) be an (πΎ, πΏ)-bifuzzy Lie subalgebra of πΏ; then the nonzero set πΏ(0, 1) is a Lie subalgebra of πΏ. Proof. Let π₯, π¦ β πΏ(0, 1). Then ππ΄ (π₯) > 0 and ]π΄(π₯) < 1, ππ΄ (π¦) > 0 and ]π΄(π¦) < 1. Assume that ππ΄ (π₯ + π¦) = 0 and ]π΄(π₯ + π¦) = 1. If πΎ β {β, β β¨π}, then we can see that π₯(ππ΄ (π₯), ]π΄(π₯))πΎπ΄ and π¦(ππ΄ (π¦), ]π΄(π¦))πΎπ΄, but (π₯ + π¦)(min{ππ΄ (π₯), ]π΄(π₯)}, max{ππ΄ (π¦), ]π΄(π¦)})πΏπ΄ for all πΏ β {β , β β¨π, β β§π}, a contradiction. Also, π₯(1, 0)ππ΄ and π¦(1, 0)ππ΄, but (π₯+π¦)(1, 0)πΏπ΄ for all πΏ β {β, β β¨π, β β§π}, a contradiction. Thus ππ΄ (π₯+π¦) > 0 and ]π΄(π₯+π¦) < 1. Thus π₯+π¦ β πΏ(0, 1). For other conditions the verification is analogous. Consequently πΏ(0, 1) is a Lie subalgebra of πΏ. Definition 17. A bifuzzy set π΄ = (ππ΄ , ]π΄) in πΏ is called an (β, β β¨π)-bifuzzy Lie algebra of πΏ if it satisfies the following conditions: (f) π₯(π 1 , π‘1 ) β π΄, π¦(π 2 , π‘2 ) β π΄ β (π₯ + π¦)(min(π 1 , π 2 ), max(π‘1 , π‘2 )) β β¨ππ΄, (g) π₯(π , π‘) β π΄ β (ππ₯)(π , π‘) β β¨ππ΄, (h) π₯(π 1 , π‘1 ) β π΄, π¦(π 2 , π‘2 ) β π΄ β [π₯, π¦](max(π 1 , π 2 ), min(π‘1 , π‘2 )) β β¨ππ΄ for all π₯, π¦ β πΏ, π β πΉ, π , π 1 , π 2 β (0, 1], π‘, π‘1 , π‘2 β [0, 1). Theorem 18. Let π΄ = (ππ΄ , ]π΄) be a bifuzzy set in a Lie algebra πΏ. Then π΄ is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ if and only if (i) ππ΄ (π₯ + π¦) β©Ύ min(ππ΄ (π₯), ππ΄ (π¦), 0.5), ]π΄(π₯ + π¦) β©½ max(]π΄(π₯), ]π΄(π¦), 0.5),
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The Scientific World Journal (j) ππ (ππ₯) β©Ύ min(ππ΄ (π₯), 0.5), ]π (ππ₯) β©½ max(]π΄(π₯), 0.5), (k) ππ΄ ([π₯, π¦]) β©Ύ max(ππ΄ (π₯), ππ΄ (π¦), 0.5), ]π΄([π₯, π¦]) β©½ min(]π΄(π₯), ]π΄(π¦), 0.5)
hold for all π₯, π¦ β πΏ, π β πΉ. Proof. (f)β(i): Let π₯, π¦ β πΏ. We consider the following two cases: (1) min(ππ΄ (π₯), ππ΄ (π¦)) < 0.5, max(]π΄(π₯), ]π΄(π¦)) > 0.5, (2) min(ππ΄ (π₯, ππ΄ (π¦)) β©Ύ 0.5, max(]π΄(π₯, ]π΄(π¦)) β©½ 0.5. Case 1. Assume that ππ΄ (π₯ + π¦) < min(ππ΄ (π₯), ππ΄ (π¦), 0.5), ]π΄(π₯ + π¦) > max(]π΄(π₯), ]π΄(π¦), 0.5). Then ππ΄ (π₯ + π¦) < min(ππ΄ (π₯), ππ΄ (π¦)), ]π΄(π₯ + π¦) > max(]π΄(π₯), ]π΄(π¦)). Take π , π‘ such that ππ΄ (π₯ + π¦) < π < min(ππ΄ (π₯), ππ΄ (π¦)), ]π΄(π₯ + π¦) > π‘ > max(]π΄(π₯), ]π΄(π¦)). Then π₯π , π¦π β ππ΄ and π₯π‘ , π¦π‘ β ]π΄, but (π₯ + π¦)(min(π 1 , π 2 ), max(π‘1 , π‘2 ))β β¨ππ΄, which is contradiction with (π). Case 2. Assume that ππ΄ (π₯ + π¦) < 0.5, ]π΄(π₯ + π¦) > 0.5. Then π₯(0.5, 0.5), π¦(0.5, 0.5) β π΄ but (π₯ + π¦)(0.5, 0.5)β β¨ππ΄, a contradiction. Hence (i) holds. (i) β (f): Let π₯(π 1 , π‘1 ), π¦(π 2 , π‘2 ) β π΄; then ππ΄ (π₯) β©Ύ π 1 , ππ΄ (π¦) β©Ύ π 2 , ]π΄(π₯) β©½ π‘1 , ]π΄(π¦) β©½ π‘2 . Now, we have ππ΄ (π₯ + π¦) β©Ύ min (ππ΄ (π₯) , ππ΄ (π¦) , 0.5) β©Ύ min (π 1 , π 2 , 0.5) , ]π΄ (π₯ + π¦) β©½ max (]π΄ (π₯) , ]π΄ (π¦) , 0.5) β©½ max (π‘1 , π‘2 , 0.5) . (10) If min(π 1 , π 2 ) > 0.5, max(π‘1 , π‘2 < 0.5, then ππ΄ (π₯ + π¦) β©Ύ 0.5 β ππ΄ (π₯ + π¦) + min(π 1 , π 2 ) > 1, ]π΄(π₯ + π¦) β©½ 0.5 β ]π΄(π₯ + π¦) + max(π‘1 , π‘2 ) < 1. On the other hand, if min(π 1 , π 2 ) β©½ 0.5, max(π‘1 , π‘2 ) β©Ύ 0.5, then ππ΄ (π₯ + π¦) β©Ύ min(π 1 , π 2 ), ]π΄(π₯ + π¦) β©½ max(π‘1 , π‘2 ). Hence (π₯+π¦)(min(π 1 , π 2 ), max(π‘1 , π‘2 )) β β¨ππ΄. The verification of (g) β (j) and (h) β (k) is analogous and we omit the details. This completes the proof. Theorem 19. Let π΄ = (ππ΄ , ]π΄) be a bifuzzy set of Lie algebra of πΏ. Then π΄ is an (β, β β¨π)-bifuzzy Li subalgebra of πΏ if and only if each nonempty π΄ (π ,π‘) , π β (0.5, 1], π‘ β [0.5, 1) is a Lie subalgebra of πΏ. Proof. Assume that π΄ = (ππ΄ , ]π΄) is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ and let π β (0.5, 1], π‘ β [0.5, 1). If π₯, π¦ β π΄ (π ,π‘) and π β πΉ, then ππ΄(π₯) β₯ π and ππ΄ (π¦) β₯ π , ]π΄(π₯) β€ π‘ and ]π΄(π¦) β€ π‘. Thus, ππ΄ (π₯ + π¦) β©Ύ min (ππ΄ (π₯) , ππ΄ (π¦) , 0.5) β©Ύ min (π , 0.5) = π , ]π΄ (π₯ + π¦) β©½ max (]π΄ (π₯) , ]π΄ (π¦) , 0.5) β©½ max (π‘, 0.5) = π‘, ππ΄ (ππ₯) β©Ύ min (ππ΄ (π₯) , 0.5) β©Ύ min (π , 0.5) = π , ]π΄ (ππ₯) β©½ max (]π΄ (π₯) , 0.5) β©½ max (π‘, 0.5) = π‘, ππ΄ ([π₯, π¦]) β©Ύ min (ππ΄ (π₯) , ππ΄ (π¦) , 0.5) β©Ύ min (π‘, 0.5) = π‘, ]π΄ ([π₯, π¦]) β©½ max (]π΄ (π₯) , ]π΄ (π¦) , 0.5) β©½ max (π‘, 0.5) = π‘, (11)
and so π₯ + π¦, ππ₯, [π₯, π¦] β π΄ (π ,π‘) . This shows that πΏ(]; π‘) are Lie subalgebras of πΏ. The proof of converse part is obvious. This ends the proof. Theorem 20. Let π΄ be a bifuzzy set in a Lie algebra πΏ. Then π΄ (π ,π‘) is a Lie subalgebra of πΏ if and only if (1) max(ππ΄ (π₯+π¦), 0.5) β©Ύ min(ππ΄ (π₯), ππ΄ (π¦)), min(]π΄(π₯+ π¦), 0.5) β©½ max(]π΄(π₯), ]π΄(π¦)), (2) max(ππ΄ (ππ₯), 0.5) β©Ύ ππ΄ (π₯), min(]π΄(ππ₯), 0.5) β©½ ]π΄(π₯), (3) max(ππ΄ ([π₯, π¦]), 0.5)) β©Ύ min(ππ΄ (π₯), ππ΄ (π¦)), min(]π΄([π₯, π¦]), 0.5)) β©½ max(]π΄(π₯), ]π΄(π¦)) for all π₯, π¦ β πΏ, π β πΉ. Proof. Suppose that π΄ (π ,π‘) is a Lie subalgebra of πΏ. Let max(ππ΄ (π₯ + π¦), 0.5) < min(ππ΄ (π₯), ππ΄ (π¦)) = π , min(]π΄(π₯ + π¦), 0.5) > max(]π΄(π₯), ]π΄(π¦)) = π‘ for some π₯, π¦ β πΏ; then π β (0.5, 1], π‘ β [0.5, 1), ππ΄ (π₯ + π¦) < π , ]π΄(π₯ + π¦) > π‘, π₯, π¦ β π΄ (π ,π‘) . Since π₯, π¦ β π΄ (π ,π‘) and π΄ (π ,π‘) is a Lie subalgebra of πΏ, so π₯ + π¦ β π΄ (π ,π‘) or ππ΄ (π₯ + π¦) β©Ύ π , ]π΄(π₯ + π¦) β©½ π‘, which is contradiction with ππ΄ (π₯ + π¦) < π , ]π΄(π₯ + π¦) > π‘. Hence (1) holds. For (2), (3) the verification is analogous. Conversely, suppose that (1)β(3) hold. Assume that π β (0.5, 1], π‘ β [0.5, 1), π₯, π¦ β π΄ (π ,π‘) . Then 0.5 < π β©½ min (ππ΄ (π₯) , ππ΄ (π¦)) β©½ max (ππ΄ (π₯ + π¦) , 0.5) σ³¨β ππ΄ (π₯ + π¦) β©Ύ π , 0.5 > π‘ β©Ύ max (]π΄ (π₯) , ]π΄ (π¦)) β©Ύ min (]π΄ (π₯ + π¦) , 0.5) σ³¨β ]π΄ (π₯ + π¦) β©½ π‘, 0.5 < π β©½ ππ΄ (π₯) β©½ max (ππ΄ (ππ₯) , 0.5) σ³¨β ππ΄ (ππ₯) β©Ύ π , 0.5 > π‘ β©Ύ ]π΄ (π₯) β©Ύ min (]π΄ (ππ₯) , 0.5) σ³¨β ]π΄ (ππ₯) β©½ π‘, 0.5 < π β©½ min (ππ΄ (π₯) , ππ΄ (π¦)) β©½ max (ππ΄ [π₯, π¦] , 0.5) σ³¨β ππ΄ ([π₯, π¦]) β©Ύ π , 0.5 > π‘ β©Ύ max (]π΄ (π₯) , ]π΄ (π¦)) β©Ύ min (]π΄ [π₯, π¦] , 0.5) σ³¨β ]π΄ ([π₯, π¦]) β©½ π‘, (12) and so π₯ + π¦, ππ₯, [π₯, π¦] β π΄ (π ,π‘) . This shows that π΄ (π ,π‘) is a Lie subalgebra of πΏ. Theorem 21. The intersection of any family of (β, β β¨π)bifuzzy Lie subalgebras of πΏ is an (β, β β¨π)-bifuzzy Lie subalgebra. Proof. Let {π΄ π : π β Ξ} be a family of (β, β β¨π)-bifuzzy Lie subalgebra of πΏ and let π΄ := βπβΞ π΄ π = (supπβΞ ππ , inf πβΞ ]π ). Let π₯, π¦ β πΏ, then by Theorem 19, we have ππ΄ (π₯ + π¦) β©Ύ
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min(ππ΄ (π₯), ππ΄ (π¦), 0.5), ]π΄(π₯ + π¦) β©½ max(]π΄(π₯), ]π΄(π¦), 0.5), and hence ππ΄ (π₯ + π¦) = sup ππ (π₯ + π¦)
(d) π΄ is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ if and only Μ] are Lie subalgebras if nonempty subsets β¨ππ΄ β©π and [] π΄ π of πΏ for all π β (0.5, 1] and π β (0, 1];
β©Ύ sup min (ππ (π₯) , ππ (π¦) , 0.5)
(e) π΄ is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ if and only if nonempty subsets [ππ΄ ]π and ]Μπ΄π are Lie subalgebras of πΏ for all π β (0, 1] and π β (0.5, 1];
= min (sup ππ (π₯) , sup ππ (π¦) , 0.5)
(f) π΄ is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ if and only ]π΄]π are ideals of πΏ for if nonempty subsets [ππ΄ ]π and [Μ all π, π β (0, 1].
πβΞ
πβΞ
πβΞ
πβΞ
4. Bifuzzy Soft Lie Algebras
= min (β ππ (π₯) , β ππ (π¦) , 0.5) πβΞ
πβΞ
In this section, we introduce bifuzzy soft Lie subalgebras and investigate some of their properties.
= min (ππ΄ (π₯) , ππ΄ (π¦) , 0.5) , ]π΄ (π₯ + π¦) = inf ]π (π₯ + π¦)
Definition 24. Let πΏ be a Lie algebra and let (π, π΄) be a bifuzzy soft set over πΏ. Then (π, π΄) is said to be a bifuzzy soft Lie subalgebra over πΏ if π(π₯) is a bifuzzy Lie subalgebra of πΏ for all π₯ β π΄; that is, a bifuzzy soft set (π, π΄) on πΏ is called a bifuzzy soft Lie subalgebra of πΏ if
πβΞ
β©½ inf max (]π (π₯) , ]π (π¦) , 0.5) πβΞ
= max (inf ]π (π₯) , inf ]π (π¦) , 0.5) πβΞ
πβΞ
(a) πππ (π₯ + π¦) β©Ύ min{πππ (π₯), πππ (π¦)},
(b) ]ππ (π₯ + π¦) β©½ max{]ππ (π₯), ]ππ (π¦)},
= max (β ]π (π₯) , β ]π (π¦) , 0.5) πβΞ
(c) πππ (ππ₯) β©Ύ πππ (π₯),
πβΞ
(d) ]ππ (ππ₯) β©½ πππ (π₯),
= max (]π΄ (π₯) , ]π΄ (π¦) , 0.5) . (13) For other conditions the verification is analogous. By Theorem 19, it follows that π΄ is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ. Theorem 22. Let πΏ 0 β πΏ 1 β β
β
β
β πΏ π = πΏ be a strictly increasing chain of (β, β)-bifuzzy Lie subalgebras of a Lie algebra πΏ; then there exists (β, β)-bifuzzy Lie subalgebra π΄ = (ππ΄ , ]π΄) of πΏ whose level subalgebras are precisely the members of the chain with π΄ 0.5 = (π0.5 , ]0.5 ) = πΏ(0, 1).
(e) πππ ([π₯, π¦]) β©Ύ min{πππ (π₯), πππ (π¦)}, (f) ]ππ ([π₯, π¦]) β©½ max{]ππ (π₯), ]ππ (π¦)}
hold for all π₯, π¦ β πΏ and π β πΎ. Example 25. Let R2 = {(π₯, π¦) : π₯, π¦ β R} be the set of all 2-dimensional real vectors. Then R2 with [π₯, π¦] = π₯ Γ π¦ is a real Lie algebra. Let N and Z denote the set of all natural numbers and the set of all integers, respectively. Define π : 2 Z β ([0, 1] Γ [0, 1])R by π(π) = ππ : R2 β [0, 1] Γ [0, 1] for all π β Z,
For any π, π β [0, 1] and fuzzy subset π in πΏ, denotes ππΜ = {π₯ β πΏ | π(π₯) > π}, β¨πβ©π = {π₯ β πΏ | π₯π ππ}, [π]π = {π₯ β πΏ | Μ = {π₯ β πΏ | π₯π β β¨ππ}, Μ]π = {π₯ β πΏ | π(π₯) < π }, and []] π (π,π ) Μ π₯π β β¨ π]}. Clearly, π΄ = ππ΄Μπ β© π for all π, π β [0, 1]. π΄π We state here a nice characterization without proof. Theorem 23. Let πΏ be a Lie algebra and π΄ a bifuzzy set in πΏ. Then (a) π΄ is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ if and only if nonempty subsets ππ΄Μπ and ]Μπ΄π are Lie subalgebras of πΏ for all π β [0, 0.5) and π β (0.5, 1]; (b) π΄ is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ if and only Μ] are Lie subalgebras if nonempty subsets ππ΄Μπ and [] π΄ π of πΏ for all π β [0, 0.5) and π β (0, 1]; (c) π΄ is an (β, β β¨π)-intuitionistic fuzzy Lie subalgebra of πΏ if and only if nonempty subsets β¨ππ΄ β©π and ]Μπ΄π are πΎsubalgebras of K for all π, π β (0.5, 1];
0.6 { { πππ (π₯) = {0.2 { {0
if π₯ = (0, 0) = 0, if π₯ = (0, π) , π =ΜΈ 0, otherwise,
0.0 { { ]ππ (π₯) = {0.4 { {0.6
if π₯ = (0, 0) = 0, if π₯ = (0, π) , π =ΜΈ 0, otherwise.
(14)
By routine computations, we can easily check that (π, Z) is a bifuzzy soft Lie subalgebra of R2 . The following proposition is obvious. Proposition 26. Let (π, π΄) be a bifuzzy soft Lie subalgebra of πΏ; then (i) πππ (0) β©Ύ πππ (π₯),
(ii) ]ππ (0) β©½ ]ππ (π₯) for all π₯ β πΏ.
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Definition 27. Let (π, π΄) be a bifuzzy soft set over π. For each π , π‘ β [0, 1], the set (π, π΄)(π ,π‘) = (π(π ,π‘) , π΄) is called an (π , π‘)level soft set of (π, π΄), where ππ(π ,π‘) = {π₯ β π | πππ (π₯) β₯ π , ]ππ (π₯) β€ π‘} for all π β π΄. Theorem 28. Let (π, π΄) be a bifuzzy soft set over πΏ. (π, π΄) is a bifuzzy soft Lie subalgebra if and only if (π, π΄)(π ,π‘) is a soft Lie subalgebra over πΏ for each π , π‘ β [0, 1]. Proof. Suppose that (π, π΄) is a bifuzzy soft Lie subalgebra. For each π , π‘ β [0, 1], π β π΄, and π₯1 , π₯2 β (π, π΄)(π ,π‘) π , then πππ (π₯1 ) β₯ π , πππ (π₯2 ) β₯ π and ]ππ (π₯1 ) β€ π‘, ]ππ (π₯2 ) β€ π‘. From Definition 27, it follows that (π, π΄)(π ,π‘) is a bifuzzy Lie subalgebra over πΏ. Thus π πππ (π₯1 +π₯2 ) β₯ min(πππ (π₯1 ), πππ (π₯2 )), πππ (π₯1 +π₯2 ) β₯ π , ]ππ (π₯1 + π₯2 ) β€ max(]ππ (π₯1 ), ]ππ (π₯2 )), ]ππ (π₯1 +π₯2 ) β€ π‘. This implies that π₯1 +π₯2 β (π, π΄)(π ,π‘) π . Verification for other conditions is similar. is a Lie Hence we omit the details. This shows that (π, π΄)(π ,π‘) π subalgebra over πΏ. According to Definition 27, (π, π΄)(π ,π‘) is a soft Lie subalgebra over πΏ for each π , π‘ β [0, 1]. Conversely, assume that (π, π΄)(π ,π‘) is a soft Lie subalgebra over πΏ for each π , π‘ β [0, 1]. For each π β π΄ and π₯1 , π₯2 β πΏ, let π = min{πππ (π₯1 ), πππ (π₯2 )} and let π‘ = max{]ππ (π₯1 ), ]ππ (π₯2 )}; (π ,π‘) then π₯1 , π₯2 β (π, π΄)(π ,π‘) is a Lie subalgebra π . Since (π, π΄)π (π ,π‘) over πΏ, then π₯1 +π₯2 β (π, π΄)π . This means that πππ (π₯1 +π₯2 ) β₯ min(πππ (π₯1 ), πππ (π₯2 )), ]ππ (π₯1 + π₯2 ) β€ max(]ππ (π₯1 ), ]ππ (π₯2 )). Verification for other conditions is similar. Hence we omit is a bifuzzy Lie subalgebra over the details. Thus, (π, π΄)(π ,π‘) π πΏ. According to Definition 24, (π, π΄) is a bifuzzy soft Lie subalgebra over πΏ. This completes the proof. Definition 29. Let π : π β π and π : π΄ β π΅ be two functions, where π΄ and π΅ are parametric sets from the crisp sets π and π, respectively. Then the pair (π, π) is called a bifuzzy soft function from π to π. Definition 30. Let (π, π΄) and (π, π΅) be two bifuzzy soft sets over πΏ 1 and πΏ 2 , respectively, and let (π, π) be a bifuzzy soft function from πΏ 1 to πΏ 2 . (1) The image of (π, π΄) under the bifuzzy soft function (π, π), denoted by (π, π)(π, π΄), is the bifuzzy soft set on πΏ 2 defined by (π, π)(π, π΄) = (π(π), π(π΄)), where for all π β π(π΄), π¦ β πΏ 2 { { β β ππ (π₯) ππ(π)π (π¦) = {π(π₯)=π¦π(π)=π { {1 { { β β ππ (π₯) ]π(π)π (π¦) = {π(π₯)=π¦π(π)=π { {0
over πΏ 1 defined by (π, π)β1 (π, π΅) = (πβ1 (π), πβ1 (π΅)), where for all π β πβ1 (π΄), for all π₯ β πΏ 1 , ππβ1 (π)π (π₯) = πππ(π) (π (π₯)) , ]πβ1 (π)π (π₯) = ]ππ(π) (π (π₯)) .
(16)
Definition 31. Let (π, π) be a bifuzzy soft function from πΏ 1 to πΏ 2 . If π is a homomorphism from πΏ 1 to πΏ 2 , then (π, π) is said to be bifuzzy soft homomorphism. If π is a isomorphism from πΏ 1 to πΏ 2 and π is one-to-one mapping from π΄ onto π΅ then (π, π) is said to be bifuzzy soft isomorphism. Theorem 32. Let (π, π΅) be a bifuzzy soft Lie subalgebra over πΏ 2 and let (π, π) be a bifuzzy soft homomorphism from πΏ 1 to πΏ 2 . Then (π, π)β1 (π, π΅) is a bifuzzy soft Lie subalgebra over πΏ 1 . Proof. Let π₯1 , π₯2 β πΏ 1 ; then πβ1 (πππ ) (π₯1 + π₯2 ) = πππ(π) (π (π₯1 + π₯2 )) = πππ(π) (π (π₯1 ) + π (π₯2 )) β©Ύ min {πππ(π) (π (π₯1 )) , πππ(π) (π (π₯2 ))} = min {πβ1 (πππ ) (π₯1 ) , πβ1 (πππ ) (π₯2 )} , πβ1 (]ππ ) (π₯1 + π₯2 )
(17)
= ]ππ(π) (π (π₯1 + π₯2 )) = ]ππ(π) (π (π₯1 ) + π (π₯2 )) β©½ max {]ππ(π) (π (π₯1 )) , ]ππ(π) (π (π₯2 ))} = max {πβ1 (]ππ ) (π₯1 ) , πβ1 (]ππ ) (π₯2 )} . Verification for other conditions is similar. Hence we omit the details. Hence (π, π)β1 (π, π΅) is a bifuzzy soft Lie subalgebra over πΏ 1 . Remark 33. Let (π, π΄) be a bifuzzy soft Lie subalgebra over πΏ 1 and let (π, π) be a bifuzzy soft homomorphism from πΏ 1 to πΏ 2 . Then (π, π)(π, π΄) may not be a bifuzzy soft Lie subalgebra over πΏ 2 . Theorem 34. Let (π, π΄) be a bifuzzy soft Lie subalgebra over πΏ and let {(βπ , π΅π ) | π β πΌ} be a nonempty family of bifuzzy soft Lie subalgebras of (π, π΄). Then
if π₯ β πβ1 (π¦) , otherwise, (15) β1
if π₯ β π (π¦) , otherwise.
Μ (β , π΅ ) is a bifuzzy soft Lie subalgebra of (π, π΄); (a) β πβπΌ π π (b) βπβπΌ (βπ , π΅π ) is a bifuzzy soft Lie subalgebra of βπβπΌ (π, π΄); Μ (π» , π΅ ) is an (c) if π΅π β© π΅π = 0 for all π, π β πΌ, then β π π πβπΌ Μ (π, π΄). bifuzzy soft Lie subalgebra of β πβπΌ
(2) The preimage of (π, π΅) under the bifuzzy soft function (π, π), denoted by (π, π)β1 (π, π΅), is the bifuzzy soft set
As a generalization of above theorem, we have the following result.
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Theorem 35. Let (π, π΄) be an (β, β β¨π)-bifuzzy soft Lie subalgebra over πΏ and let {(βπ , π΅π ) | π β πΌ} be a nonempty family of (β, β β¨π)-bifuzzy soft πΎ-subalgebras of (π, π΄); then Μ (β , π΅ ) is an (β, β β¨π)-bifuzzy soft Lie subalgebra (a) β πβπΌ π π of (π, π΄); (b) βπβπΌ (βπ , π΅π ) is an (β, β β¨π)-bifuzzy soft Lie subalgebra of βπβπΌ (π, π΄); Μ (π» , π΅ ) is an (c) if π΅ β© π΅ = 0 for all π, π β πΌ, then β π
π
πβπΌ
π
π
Μ (π, π΄). (β, β β¨π)- bifuzzy soft Lie subalgebra of β πβπΌ
Theorem 36. Let (π, π΄) and (π, π΅) be two (β, β β¨π)-bifuzzy Μ (π, π΅) is soft πΎ-subalgebras over a Lie algebra πΏ. Then (π, π΄) β© an (β, β β¨π)-bifuzzy soft Lie subalgebra over πΏ. Μ (π, π΅) = (β, πΆ), Proof. By Definition 12, we can write (π, π΄) β© where πΆ = π΄ βͺ π΅ and π (πΌ) if πΌ β π΄ β π΅, { { β (πΌ) = {π (πΌ) if πΌ β π΅ β πΆ, { π β© π if πΌ β π΄ β© π΅, (πΌ) (πΌ) {
Μ , β©) is a complete distributive latTheorem 40. (FSI(πΊ, πΈ), βͺ tice under the ordering relation β. Proof. For any (π, π΄), (π, π΄) β FSI(πΊ, πΈ), by above Lemmas, Μ (π, π΄) β FSI(πΊ, πΈ) and (π, π΄) β© (π, π΄) β FSI(πΊ, πΈ). (π, π΄) βͺ Μ (π, π΄) and (π, π΄) β© (π, π΄) are the It is obvious that (π, π΄) βͺ least upper bound and the greatest lower bound of (π, π΄) and (π, π΅), respectively. There is no difficulty in replacing {(π, π΄), (π, π΄)} with an arbitrary family of FSI(πΊ, πΈ) and so Μ , β©) is a complete lattice. Now we prove that the (FSI(πΊ, πΈ), βͺ following distributive law Μ (β, πΆ)) (π, π΄) β© ((π, π΄) βͺ Μ ((π, π΄) β© (β, πΆ)) = ((π, π΄) β© (π, π΄)) βͺ
holds for all (π, π΄), (π, π΄), (β, πΆ) β FSI(πΊ, πΈ). Suppose that Μ (β, πΆ)) = (πΌ, π΄ β© (π΅ βͺ πΆ)) , (π, π΄) β© ((π, π΄) βͺ Μ ((π, π΄) β© (β, πΆ)) ((π, π΄) β© (π, π΅)) βͺ
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= (π½, (π΄ β© π΅) βͺ (π΄ β© πΆ))
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= (π½, π΄ β© (π΅ βͺ πΆ)) .
for all πΌ β πΆ. Now for any πΌ β πΆ, we consider the following cases.
Now for any π β π΄ β© (π΅ βͺ πΆ), it follows that π β π΄ and π β π΅ βͺ πΆ. We consider the following cases.
Case 1. Consider (πΌ β π΄ β π΅). Then β(πΌ) = π(πΌ) is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ since (π, π΄) is an (β, β β¨π)bifuzzy soft Lie subalgebra over πΏ.
Case 1. Consider (π β π΄, π β π΅ and π β πΆ). Then πΌ(π) = π(π) β© β(π) = π½(π).
Case 2. Consider (πΌ β π΅ β π΄). Then β(πΌ) = π(πΌ) is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ since (π, π΅) is an (β, β β¨π)bifuzzy soft Lie subalgebra over πΏ. Case 3. Consider (πΌ β π΄ β© π΅). Then β(πΌ) = π(πΌ) β© π(πΌ) is an (β, β β¨π)-bifuzzy Lie subalgebra of πΏ by the assumption. Thus, in any case, β(πΌ) is an (β, β β¨π)-bifuzzy Lie subalgebra Μ (π, π΅) is an (β, β β¨π)-bifuzzy soft Lie of πΏ. Therefore, (π, π΄) β© subalgebra over πΏ. Theorem 37. Let (π, π΄) and (π, π΅) be two (β, β β¨π)-bifuzzy soft πΎ-subalgebras over a Lie algebra πΏ. If π΄ and π΅ are disjoint, Μ (π, π΅) is an (β, β β¨π)-bifuzzy softLie subalgebra then (π, π΄) βͺ over πΏ. Lemma 38. Let πΏ be a Lie algebra and (π, π΄) and (π, π΅) intuitionistic bifuzzy soft sets on πΊ. If (π, π΄) and (π, π΅) are (β, β β¨π)-intuitionistic bifuzzy soft Lie subalgebra on πΏ, then Μ (π, π΅). Moreover, if (π, π΄) so are (π, π΄) β© (π, π΅) and (π, π΄) β© and (π, π΅) are an (β, β β¨π)-bifuzzy soft Lie subalgebra on πΏ and an (β, β β¨π)-bifuzzy soft Lie subalgebra on πΏ, then Μ (π, π΅). (π, π΄)ββ (π, π΅) β (π, π΄) β© Lemma 39. Let πΏ be a Lie algebra and (π, π΄) and (π, π΅) bifuzzy soft sets on πΏ. If (π, π΄) and (π, π΅) are (β, β β¨π)bifuzzy soft Lie subalgebra on πΏ, then so are (π, π΄) βͺ (π, π΅) and Μ (π, π΅). (π, π΄) βͺ Denote by SI(πΊ, πΈ) the set of all (β, β β¨π)-bifuzzy soft Lie subalgebras on πΏ.
Case 2. Consider (π β π΄, π β π΅ and π β πΆ). Then πΌ(π) = π(π) β© πΊ(π) = π½(π). Case 3. Consider (π β π΄, π β π΅ and π β πΆ). Then πΌ(π) = π(π) β© (π(π) βͺ β(π)) = (π(π) β© π(π)) βͺ (π(π) β© β(π)) = π½(π). Therefore, πΌ and π½ are the same operators, and so (π, π΄) β© Μ (β, πΆ)) = ((π, π΄) β© (π, π΅)) βͺ Μ ((π, π΄) β© (β, πΆ)). ((π, π΄) βͺ Μ (β, πΆ)) = ((π, π΄) β© It follows that (π, π΄) β© ((π, π΄) βͺ Μ ((π, π΄) β© (β, πΆ)). This completes the proof. (π, π΅)) βͺ Definition 41. The product of two bifuzzy soft sets (π, π΄) and (π, π΄) over a Lie algebra is a bifuzzy soft set over πΊ, denoted by (π β π, πΆ), where πΆ = π΄ βͺ π΅ and π (π) if π β π΄ β π΅, { { (π β π) (π) = {π (π) (21) if π β π΅ β π΄, { {π (π) β πΊ (π) if π β π΄ β© π΅, for all π β πΆ. This is denoted by (π β π, πΆ) = (π, π΄) β (π, π΄). The following results can be easily deduced. Lemma 42. Let (π1 , π΄), (π2 , π΄), (π1 , π΅), and (π2 , π΅) be bifuzzy soft sets over a Lie algebra πΏ such that (π1 , π΄) β (π2 , π΄) and (π1 , π΅) β (π2 , π΅). Then (a) (π1 , π΄) β (π1 , π΅) β (π2 , π΄) β (π2 , π΅), Μ (b) (π1 , π΄) β© (π1 , π΅) β (π2 , π΄) β© (π2 , π΅) and (π1 , π΄) β© Μ (π2 , π΅), (π1 , π΅) β (π2 , π΄) β© Μ (c) (π1 , π΄) βͺ (π1 , π΅) β (π2 , π΄) βͺ (π2 , π΅) and (π1 , π΄) βͺ Μ (π1 , π΅) β (π2 , π΄) βͺ (π2 , π΅).
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Lemma 43. Let (π, π΄), (π, π΄), and (β, πΆ) be bifuzzy soft sets over a Lie algebra πΏ. Then (πΉ, π΄) β ((π, π΄) β (β, πΆ)) = ((π, π΄) β (π, π΅)) β (β, πΆ). Now we consider the bifuzzy soft sets over a definite parameter set. Let π΄ β πΈ, πΏ be a Lie algebra and FSπ΄ (πΊ) = {(π, π΄) β FSI (πΊ, πΈ) | πΉ : π΄ σ³¨β F (π)}
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the set of bifuzzy soft sets over πΏ and the parameter set π΄. It Μ (πΊ, π΄), (π, π΄) β© Μ (π, π΄), (π, π΄) βͺ is trivial to verify that (π, π΄) βͺ (π, π΄), (π, π΄)β©(π, π΄) β FSπ΄ (πΊ) for all (π, π΄), (π, π΄) β FSπ΄(πΊ). Theorem 44. Let (π, π΄) and (π, π΄) be (β, β β¨π)-bifuzzy soft Lie subalgebra over a Lie algebra πΏ. Then so is (π, π΄) β (π, π΄). Theorem 45. Let πΏ be a Lie algebra with an identity π. Then (FSI(πΊ, πΈ), β, β©) is a complete lattice under the relation β.
5. Conclusions Presently, science and technology are featured with complex processes and phenomena for which complete information is not always available. For such cases, mathematical models are developed to handle various types of systems containing elements of uncertainty. A large number of these models are based on an extension of the ordinary set theory such as bifuzzy sets and soft sets. In the current paper, we have presented the basic properties on bifuzzy soft Lie subalgebras. The most of these properties can be simply extended to bifuzzy soft Lie ideals. A Lie algebra is known algebraic structure and there are still many unsolved problems in it. In our opinion the future study of Lie algebras can be extended with the study of (i) roughness in Lie algebras and (ii) fuzzy rough Lie algebras.
Acknowledgment This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under Grant no. 1433/363/124. The authors, therefore, acknowledge with thanks DSR technical and financial support.
References [1] P. Coelho and U. Nunes, βLie algebra application to mobile robot control: a tutorial,β Robotica, vol. 21, no. 5, pp. 483β493, 2003. [2] L. A. Zadeh, βFuzzy sets,β Information and Control, vol. 8, no. 3, pp. 338β353, 1965. [3] K. T. Atanassov, βIntuitionistic fuzzy sets,β VII ITKRβs Session, Sofia, June 1983, Deposed in Central Science-Technology Library of Bulgarian Academy of Sciences, 1697/84 (Bulgarian). [4] T. Gerstenkorn and J. MaΒ΄nko, βBifuzzy probabilistic sets,β Fuzzy Sets and Systems, vol. 71, no. 2, pp. 207β214, 1995. [5] D. Molodtsov, βSoft set theoryβfirst results,β Computers and Mathematics with Applications, vol. 37, no. 4-5, pp. 19β31, 1999. [6] P. K. Maji, R. Biswas, and A. R. Roy, βSoft set theory,β Computers and Mathematics with Applications, vol. 45, no. 4-5, pp. 555β562, 2003.
[7] P. K. Maji, R. Biswas, and A. R. Roy, βIntuitionistic fuzzy soft sets,β Journal of Fuzzy Mathematics, vol. 9, no. 3, pp. 677β692, 2001. [8] S. E.-B. Yehia, βFuzzy ideals and fuzzy subalgebras of Lie algebras,β Fuzzy Sets and Systems, vol. 80, no. 2, pp. 237β244, 1996. [9] M. Akram and F. Feng, βSoft intersection Lie algebras,β Quasigroups and Related Systems, vol. 21, pp. 1β10, 2013. [10] M. Akram, B. Davvaz, and F. Feng, βFuzzy soft Lie algebras,β Journal of Multivalued Valued and Soft Computing. In press. [11] S. Abdullah, B. Davvaz, and M. Aslam, β(πΌ, π½)-intuitionistic fuzzy ideals of hemirings,β Computers & Mathematics with Applications, vol. 62, no. 8, pp. 3077β3090, 2011. [12] M. Akram, βIntuitionistic (π, π)-fuzzy Lie ideals of Lie algebras,β Quasigroups and Related Systems, vol. 15, no. 2, pp. 201β218, 2007. [13] D. C ΒΈ oker and M. Demirci, βOn intuitionistic fuzzy points,β Notes on Intuitionistic Fuzzy Sets, vol. 1, no. 2, pp. 79β84, 1995. [14] M. I. Ali, F. Feng, X. Liu, W. K. Min, and M. Shabir, βOn some new operations in soft set theory,β Computers and Mathematics with Applications, vol. 57, no. 9, pp. 1547β1553, 2009.