Ba32759764
Transcript of Ba32759764
International Journal of Modern Engineering Research (IJMER)
www.ijmer.com Vol.3, Issue.2, March-April. 2013 pp-759-764 ISSN: 2249-6645
www.ijmer.com 759 | Page
G.Anitha, 1 M.Mariasingam
2
1Research Scholar, V.O.Chidambaram College, Tuticorin, Tamil Nadu, India
2Department of Mathematics, V.O.Chidambaram College, Tuticorin, Tamil Nadu, India
Abstract: The aim of this paper is to introduce π πΌwg-quotient map using π πΌwg-closed sets and study their basic properties.
We also study the relation between weak and strong form of π πΌwg-quotient maps. We also derive the relation between
π πΌwg-quotient maps and π πΌ -quotient maps and also derive the relation between the π πΌwg-continuous map and π πΌwg-
quotient maps. Examples are given to illustrate the results.
Keywords: π πΌ -closed sets, π πΌ -open sets, π πΌwg-closed sets, π πΌwg-open sets.
2000 Mathematics Subject Classification: 54C10, 54C08, 54C05
I. Introduction Njastad [12] introduced the concept of an Ξ±-sets and Mashhour et al [9] introduced Ξ±-continuous mappings in
topological spaces. The topological notions of semi-open sets and semi-continuity, and preopen sets and precontinuity were
introduced by Levine [5] and Mashhour et al [10] respectively. After advent of these notions, Reilly [14] and Lellis Thivagar
[1] obtained many interesting and important results on Ξ±-continuity and Ξ±-irresolute mappings in topological spaces. Lellis
Thivagar [1] introduced the concepts of Ξ±-quotient mappings and Ξ±*-quotient mappings in topological spaces. Jafari et
al.[15] have introduced π πΌ -closed set in topological spaces. The author [6] introduced π πΌ -WG closed set using π πΌ -closed set.
In this paper we have introduced π πΌ -WG quotient mappings.
II. Preliminaries Throughout this paper (X, ), (Y, ) and (Z,π) (or X, Y and Z) represent non empty topological spaces on which
no separation axiom is defined unless otherwise mentioned. For a subset A of a space the closure of A, interior of A and
complement of A are denoted by cl(A), int(A) and Ac respectively.
We recall the following definitions which are useful in the sequel.
Definition 2.1: A subset A of a space (X, t) is called:
(i)semi-open set [5] if Aβcl(int(A));
(ii) a Ξ±-open set [12] if Aβ int(cl(int(A))).
The complement of semi-open set(resp.πΌ-open set) is said to be semi closed (resp.πΌ-closed)
Definition 2.2: A subset A of a topological space(X, π)is called
(i)w-closed set [13] if cl(A)U, whenever AU and U is semi-open in (X, π).
(ii) g-closed set [16] if cl(A) U, whenever AU and U is w-open in (X, π).
(iii) a # g-semi closed set( # gs-closed)[17] if scl(A)U, whenever AU and U is g -open in (X, π).
(iv) a π πΌ -closed [15] if πΌcl(A) U, whenever AU and U is # gs-open in (X, π).
(v) a π πΌ -Weakly generalized closed set(π πΌwg-closed) [6] if Cl(Int(A)) U, whenever AU,U is π πΌ -open in (X, π).
The complements of the above sets are called their respective open sets.
Definition 2.3: A function π: π, π β (π,π) is called
(i) a πΌ-continuous [1] if f(V) is a πΌ -closed set of (X, π) for each closed set V of (Y, π).
(ii)a πΌ -irresolute [1] if f-1(V) is an πΌ -open in (X,π) for each πΌ -open set V of (Y, π).
(iii) a π πΌ -continuous [3] if f-1
(V ) is a π πΌ_-closed set of (X, π ) for each closed set V of (Y, π),
(iv)a π πΌ_-irresolute [3] if fοΏ½1(V ) is π πΌ -open in (X, π ) for each π πΌ-open set V of (Y, π),
(v)π πΌwg - continuous [7] if f -1
(V) is π πΌwg-closed in (X, π) for every closed set V of (Y, π).
(vi) π πΌwg - irresolute [7] if f -1
(v) is π πΌwg-closed in (X, π) for every π πΌwg-closed set V in (Y, π)
Definition 2.4: A space(X, π) is called ππ πΌπ€π -space [6] if every π πΌwg-closed set is closed.
Definition 2.5: A function π: π, π β (π,π) is said to be
(i)a π πΌwg -open [8]if the image of each open set in (X,π) is π πΌwg -open set in (Y,π).
(ii) a strongly π πΌwg -open or ((π πΌπ€π)β-open)[8] if the image of each π πΌwg -open set in (X,π) is a π πΌwg -open in (Y,π).
On Topological g ΜΞ±--WG Quotient Mappings
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Definition 2.6: A surjective map π: π, π β (π,π) is said to be
(i) a quotient map [4] provided a subset U of (Y,π) is open in (Y, π) if and only if f-1
(U) is open in (X, π),
(ii) An πΌ-quotient map [1] if f is πΌ -continuous and f-1
(U) is open in (X, π ) implies U is an πΌ -open in (Y, π)
(iii) An πΌβ -quotient map [1] if f is πΌ -irresolute and f-1
(U) is an πΌ -open set in (X, π ) implies U is an open set in (Y, π).
(iv) a π πΌ -quotient map[2] if f is π πΌ -continuous and f-1
(U) is open in (X,π) implies U is a π πΌ -open set in (Y,π).
(v) a strongly π πΌ -quotient map[2], provided a set U of (Y,π) is open in Y if and only if f-1
(U) is a π πΌ -open set in (X,π).
(vi) a π πΌβ-quotient map[2]if f is π πΌ -irresolute and f
-1(U) is an π πΌ -open set in (X, π ) implies U is an open set in (Y, π).
Remark 2.7: The collection of all π πΌwg-closed (π πΌwg-open sets) are denoted by πΊ πΌWG_Cl(X) and (πΊ πΌWG-O(X)),
respectively.
III. π πΆ - Weakly Generalized quotient maps. Definition 3.1: A surjective map π: π, π β (π,π) is said to be π πΌwg-quotient map if f is π πΌwg-continuous and
f-1
(V) is open in (π, π) implies V is π πΌwg-open set in (π,π).
Example3.2:Letπ = π, π, π,π , π = β ,π, π , π, π , π, π,π ,π = 1,2,3 ,π = {β ,π, 1 , 1,2 , 1,3 },
π πΌwgπ(π)={β ,X,{a},{a,c},{a,b},{a,d},{a,b,c},{a,b,d},{a,c,d}}, π πΌwgO(Y) = {β ,Y,{1},{1,2},{1,3}}
The map π: π, π β (π,π) is defined as f(a)=1, f(b)=2=f(d), f(c)=3. The map f is π πΌwg-quotient map.
Proposition 3.3: If a map π: π, π β π,π is π πΌwg-continuous and π πΌwg-open then f is π πΌwg-quotient map.
Proof: We only need to prove f-1
(V) is open in (X,π) implies V is π πΌwg-open in (Y,π). Let f-1
(V) is open in (X,π). Then f(f-
1(V)) is π πΌwg-open in(Y,π). Since f is π πΌwg-open. Hence V is π πΌwg-open in (X,π).
IV. Strong form of π πΆ - Weakly Generalized quotient maps. Definition 4.1: Let π: π, π β π,π be a surjective map. Then f is called strongly π πΌwg-quotient map provided a set U of
(π,π) is open in Y if and only if f-1
(U) is π πΌwg-open set in (X,π)
Example 4.2: Let π = π, π, π,π , π = β ,π, π , π, π , π, π, π ,π = 1,2,3 ,π = {β ,π, 1 , 2 , 1,2 }
π πΌwgπ(π)={β ,X,{a},{b},{c},{a,c},{a,b},{b,c},{a,b,c},{a,b,d},{a,c,d}}, π πΌwgO(Y) = {β ,Y,{1},{2},{1,2}}
The map π: π, π β (π,π) is defined as f(a)=1, f(b)=2=f(c), f(d)=3.The map f is strongly π πΌwg-quotient map.
Theorem 4.3: Every strongly π πΌwg-quotient map is π πΌwg-open map.
Proof: Let π: π, π β (π,π) be a strongly π πΌwg β ππ’ππ‘ππππ‘ πππ. Let V be any open set in (X,π). Since every open set is
π πΌwg-open by theorem 3.2[6]. Hence V is π πΌwg-open in π, π . That is f-1
(f(V)) is π πΌwg-open in(π, π). Since f is strongly
π πΌwg-quotient, then f(V) is open in (Y,π) and hence f(V) is π πΌwg-open in (Y,π). This shows that f is π πΌwg-open map.
Remark 4.4: Converse need not be true
Example 4.5: Let π = π, π, π,π , π = β ,π, π , π , π, π ,π = 1,2,3 ,π = {β ,π, 1 , 2 , 1,2 , 1,3 },
π πΌwgπ(π)={β ,X,{a},{b},{a,b},{a,b,c},{a,b,d}}, π πΌwgO(Y) = {β ,Y,{1},{2},{1,2},{1,3}}. π: π, π β π,π is defined by
f(a)=1=f(b), f(c)=3, f(d)=2 is a π πΌwg-open map but not a strongly π πΌwg-quotient map. Since the set {2} is open in (Y,π) but
f-1
({2})={d} is not π πΌwg-open in (X,π).
Theorem 4.6: Every strongly π πΌwg-quotient map is strongly π πΌwg-open.
Proof: Let π: π, π β π,π be a strongly π πΌwg-quotient map. Let V be a π πΌwg-open in (X,π). That is
f-1
(f(V)) is π πΌwg-open in(π, π). Since f is strongly π πΌwg-quotient, then f(V) is open in (Y,π) and hence f(V) is π πΌwg-open
in (Y,π). This shows that f is π πΌwg-open map.
Example4.7: Let π = π, π, π , π = β ,π, π , π , π, π ,π = 1,2,3 ,π = {β ,π, 1,3 }, π πΌwgπ(π)={Sβ ,X,{a},{c},{a,c}},
π πΌwgO(Y) = {β ,Y,{1},{3},{1,2},{1,3},{2,3}}. The map π: π, π β (π,π) is defined as identity map. Then f is strongly
π πΌwg-open but not strongly π πΌwg-quotient map. Since
f-1
{3}={c} is π πΌwg-open in (X,π) but {3} is not open in (Y,π).
Definition 4.8: Let π: π, π β π,π be a surjective map. Then f is called a (π πΌπ€π)β -quotient map if f is π πΌwg-irresolute
and f-1
(V) is a π πΌwg-open set in (X,π) implies V is open in (Y,π).
Example 4.9: X={a,b,c,d}, π={β ,π, π , π , π, π }, Y={1,2,3}, π = {β ,π, 1 , 3 , 1,3 }
π πΌwgπ(π)={β ,X,{a},{b},{a,b},{a,b,c},{a,b,d}}, π πΌwgO(Y) = {β ,Y,{1},{3},{1,3}}. The map π: π, π β π,π defined by
f(a)=1, f(b)=3, f(c)=2=f(d). The map f is (π πΌπ€π)β-quotient map.
Theorem 4.10: Every (π πΌπ€π)β-quotient map is π πΌwg-irresolute.
Proof: Obviously true from the definition.
Remark 4.11: Converse need not be true.
Example 4.12: X={a,b,c,d}, π = β ,π, π , π, π , π, π,π ,π = 1,2,3 ,π = {β ,π, 1 , {1,3}}
π πΌwgπ(π)={β ,X,{a},{a,c},{a,b},{a,d},{a,b,c},{a,b,d},{a,c,d}}, π πΌwgO(Y) = {β ,Y,{1},{1,2},{1,3}} Let π: π, π β π,π is defined by f({a})={1}, f({b})={2}=f({d}),f({c})={3}. The map f is π πΌwg-irresolute but not (π πΌπ€π)β-quotient map Since
f-1
{1,2}={a,b,d} is π πΌwg-open in (X,π) but the set {1,2} is not open in (Y,π).
Theorem 4.13: Every (π πΌπ€π)β-quotient map is strongly π πΌwg-open map.
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Proof: Let π: π, π β π,π be a (π πΌπ€π)β-quotient map. Let V be π πΌwg-open set in (X,π). Then f-1
(f(V)) is π πΌwg-open in
(X,π). Since f is (π πΌπ€π)β-quotient this implies that f(V) is open in (Y,π) and thus π πΌwg-open in (Y,π) and thus f(V) is
π πΌwg-open in (Y,π). Hence f is strongly π πΌwg-open.
Remark 4.14: Converse need not be true
Example 4.15: Let X={a,b,c}, π={β ,π, π , π, π , π, π }, Y={1,2,3}, π = {β ,π, 1 , 2,3 },
π πΌwgπ(π)={β ,X,{c}.{a,c},{b,c}}, π πΌwgO(Y) = {β ,Y,{1},{2},{3},{1,2},{2,3},{1,3}}
Let π: π, π β π,π be a identity map, f is strongly π πΌwg βopen map but not (π πΌπ€π)β-quotient map. since
F-1{1}={a} is π πΌwg-open in (Y,π) but the set{1} is not π πΌwg-open set in (X,π).
Proposition 4.16: Every π πΌ-irresolute (πΌ-irresolute) map is π πΌwg-irresolute.
Proof: Let U be π πΌ -closed (πΌ-closed) set in(Y,π). Since every π πΌ -closed (πΌ-closed) set is π πΌwg-closed by theorem 3.7(by
theorem 3.11)[6]. Then U is π πΌwg-closed in (Y,π). Since f is π πΌ -irresolute (πΌ-irresolute), f-1
(U) is π πΌ -closed (πΌ-closed) in
(X,π) which is π πΌwg-closed in (X,π). Hence f is π πΌwg-irresolute.
V. Comparisons Proposition 5.1:
(i) Every quotient is π πΌwg-quotient map.
(ii) Every πΌ-quotient map is π πΌwg-quotient map.
Proof: Since every continuous and πΌ-continuous map is π πΌwg-continuous by theorem 2.3 1nd 2.7[7] and every open set and
πΌ-open set is π πΌwg-open by theorem 3.11[6]. The proof follows from the definition.
Remark 5.2: Converse of the above proposition need not be true.
Example 5.3: Let X={a,b,c,d}, π = β ,π, π , π , π,π ,π = 1,2,3 ,π = {β ,π, 1,2 }
π πΌwgπ(π)={β ,X,{a},{b}, {a,b}, {a,b,c},{a,b,d}}, π πΌwgO(Y) = {β ,Y,{1},{1,2},{1,3},{2,3}}. Let π: π, π β π,π is
defined by f({a})={1}, f({b})={2},f({c})={3}=f({d}).The function f is π πΌwg-quotient but not a quotient map. Since f-
1{1}={a} is open in( X,π) but the set {1} is not open in (Y,π).
Example 5.4: Let X={a,b,c,d}, π = β ,π, π , π , π,π ,π = 1,2,3 ,π = {β ,π, 1,2 }
π πΌwgπ(π)={β ,X,{a},{b}, {a,b}, {a,b,c},{a,b,d}},πΌπ(π)= {β ,X,{a},{b}, {a,b}, {a,b,c},{a,b,d}}, π πΌwgO(Y) =
{β ,Y,{1},{1,2},{1,3},{2,3}}, πΌπ(π)= {β ,Y,{1,2}}. Let π: π, π β π,π is defined by f({a})={1},
f({b})={2},f({c})={3}=f({d}).The function f is π πΌwg-quotient but not πΌ-quotient map. Since
f-1
{1}={a} is open in( X,π) but the set {1} is not πΌ- open in (Y,π).
Theorem 5.5: Every π πΌ -quotient map is π πΌwg-quotient map.
Proof: Let π: π, π β π,π be a π πΌ -quotient map. Then f is π πΌ -continuous function. By theorem 2.5[7] every π πΌ-
continuous function is π πΌwg-continuous function, then f is π πΌwg-continuous map. Let f-1
(V) is open in (Y,π). Since every
π πΌ -open set is π πΌwg-open . Then V is π πΌwg-open in (Y,π). Hence V is π πΌwg-open in (Y,π). Hence f is π πΌwg-quotient map.
Remark 5.6: Converse need not be true:
Example 5.7: Let X={a,b,c,d}, π = β ,π, π , π, π , π, π,π , π = 1,2,3 ,π = {β ,π, 2 , 3 , 1,3 , {2,3}}
π πΌwgπ(π)={β ,X,{a},{c},{d},{a,c},{a,d},{c,d},{a,b,d},{a,c,d},{b,c,d}}, π πΌO(X) =
{β ,Y,{a},{c},{d},{a,c},{a,d},{c,d},{a,c,d}}. Let π: π, π β π,π is defined by f(a)=2, f(b)=1,f(c)=3=f(d). f is π πΌwg-
quotient map but not π πΌ -quotient map Since f-1
{1,3}={b,c,d} is π πΌwg-open in( X,π) but not π πΌ- open in (Y,π).
Theorem 5.8: Every strongly π πΌwg-quotient map is π πΌwg-quotient.
Proof: Let V be any open set in(Y,π). Since f is strongly π πΌwg-quotient, f-1
(V) is π πΌwg-open set in (X,π). Hence f is π πΌwg
continuous. Let f-1
(V) be open in (X,π). Then f-1
(V) is π πΌwg-open in (X,π). Since f is strongly π πΌwg-quotient, V is open in
(Y,π). Hence f is a π πΌwg quotient map.
Remark 5.9: Converse need not be true
Example 5.10: Let X= {a, b, c, d}, π = β ,π, π , π, π , π, π,π ,π = 1,2,3 ,π = {β ,π, 1 }
π πΌwgπ(π)={β ,X,{a},{a,c},{a,b},{a,d},{a,b,c},{a,b,d},{a,c,d}}, π πΌwgO(Y) = {β ,Y,{1},{1,2},{1,3}} Let π: π, π β π,π is defined by f({a})={1}, f({b})={3},f({c})=2=f({d}).The function f is π πΌwg-quotient but not strongly π πΌwg-quotient. Since
f-1
{1,3}={a,b} is π πΌwg-open in( X,π) but {1,3} is not open in (Y,π).
Theorem 5.11: Every strongly π πΌ-quotient map is strongly π πΌπ€π-quotient map.
Proof: Let π: π, π β π,π strongly π πΌ-quotient map. Let V be any open set in (Y,π). Since f is strongly π πΌ -quotient, f-
1(V) is π πΌ -open in (X,π). Since every π πΌ-open set is π πΌπ€π-open by theorem. Then f
-1(v) is π πΌwg-open in(X,π). Hence f is
strongly π πΌwg-quotient map.
Remark 5.12: Converse need not be true.
Example 5.13: Let X={a,b,c,d}, π = β ,π, π , π, π , π, π,π , π = 1,2,3 ,π = {β ,π, π , π , π, π , {π, π}}
π πΌwgπ(π)={β ,X,{a},{c},{d},{a,c},{a,d},{c,d},{a,b,d},{a,c,d},{b,c,d}}, π πΌO(X) =
{β ,Y,{a},{c},{d},{a,c},{a,d},{c,d},{a,c,d}}. Let π: π, π β π,π is defined by f({a})={b}, f({b})={a},f({c})=c=f({d}).
Since f-1
{a,c}={b,c,d} is π πΌwg-open in( X,π) but not π πΌ - open in (Y,π).
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Theorem 5.14: Every strongly π πΌwg quotient map is π πΌwg quotient
Proof: Let V be any open set in (Y,π). Since f is strongly π πΌwg quotient, f-1
(V) is π πΌwg-open set in(X,π). Hence f is π πΌwg-
continuous. Let f-1
(V) be open in (X,π). Then f-1
(V) is π πΌwg open in (X,π) . Since f is strongly π πΌwg-quotient V is open in
(Y,π). Hence f is a π πΌwg-quotient map.
Remark 5.15: Converse need not be true
Example 5.16: Let X={a,b,c,d}, π = β ,π, π , π, π , π, π,π ,π = 1,2,3 ,π = {β ,π, 1 }
π πΌwgπ(π)={β ,X,{a},{a,c},{a,b},{a,d},{a,b,c},{a,b,d},{a,c,d}}, π πΌwgO(Y) = {β ,Y,{1},{1,2},{1,3}} Let π: π, π β π,π is defined by f({a})={1}, f({b})={3},f({c})=2=f({d}).The function f is π πΌwg-quotient but not strongly π πΌwg-quotient. Since
f-1
{1,3}={a,b} is π πΌwg-open in( X,π) but {1,3} is not open in (Y,π).
Theorem 5.17: Every (π πΌπ€π)β-quotient map is π πΌwg-quotient map.
Proof: Let f be (π πΌπ€π)β-quotient map. Then f is π πΌwg-irresolute, by theorem 3.2[7] f is π πΌwg-continuous. Let
f-1
(V) be an open set in (X,π). Then f-1
(V) is a π πΌwg-open in(X,π). Since f is (π πΌπ€π)β-quotient, V is open in (Y,π). It means
V is π πΌwg-open in (Y,π). Therefore f is a π πΌwg-quotient map.
Remark 5.18: Converse need not be true
Example 5.19: Let X={a,b,c,d}, π = β ,π, π , π, π , π, π,π ,π = 1,2,3 ,π = {β ,π, 1 }
π πΌwgπ(π)={β ,X,{a},{a,c},{a,b},{a,d},{a,b,c},{a,b,d},{a,c,d}}, π πΌwgO(Y) = {β ,Y,{1},{1,2},{1,3}} Let π: π, π β π,π is defined by f({a})={1}, f({b})={3},f({c})=2=f({d}).The function f is π πΌwg-quotient but not ( π πΌwg)
*-quotient. Since f
-
1{1,2}={a,c,d} is π πΌwg-open in( X,π) but {1,2} is not open in (Y,π).
Theorem 5.20: Every πΌβ-quotient map is (π πΌπ€π)β-quotient map.
Proof: Let f be πΌβ-quotient map. Then f is surjective, πΌ-irresolute and f-1
(U) is πΌ-open in (X,π) implies U is open set
in(Y,π). Then U is π πΌπ€π-open in (Y,π). Since every πΌ-irresolute map is π πΌwg-irresolute by proposition 4.16 and every πΌ-
irresolute map is πΌ-continuous. Then f-1
(U) is πΌ-open which is π πΌπ€π-open in(X,π). Since f is πΌβ-quotient map, U is open in
(Y,π). Hence f is (π πΌπ€π)β-quotient map.
Remark 5.21: Converse need not be true
Example 5.22: X={a,b,c,d}, π = β ,π, π , π, π , π, π,π ,π = 1,2,3 ,π = {β ,π, 2 , 3 , 2,3 , {1,3}}
π πΌwgπ(π)={β ,X,{a},{c},{d},{a,c},{a,d},{c,d},{a,b,d},{a,c,d},{b,c,d}}, π πΌwgO(Y) = {β ,Y,{2},{3},{2,3},{1,3}},
πΌπ(π)={{d},{a,c},{a,c,d}}, πΌO(Y)={{2},{3},{2,3},{1,3}}. The map π: π, π β π,π is defined by f(a)=2,
f(b)=1,f(c)=3=f(d).The function f is ( π πΌwg)*-quotient but not (πΌ)β-quotient map. Since the set {2} is πΌ-open in (Y,π) but f
-
1{2}={a} is not πΌ -open in( X,π).
Theorem 5.23: Every (π πΌ)β quotient map is (π πΌπ€π)β-quotient map:
Proof: Let f be (π πΌ)β-quotient map. Then f is surjective, π πΌ -irresolute and f-(U) is π πΌ -open in (X,π) implies U is open
in(Y,π). Then U is π πΌwg-open in(Y,π). Since every π πΌ -irresolute map is π πΌwg-irresolute and every π πΌ -irresolute map is π πΌ-
continuous. Then f-1
(U) is π πΌ-open set which is π πΌwg-open set in(X,π). Since f is a (π πΌ)β-quotient map, U is open in (Y,π).
Hence f is a (π πΌπ€π)β-quotient map.
Remark 5.24: Converse need not be true
Example 5.25: Let X={a,b,c,d}, π = β ,π, π , π, π , π, π,π ,π = 1,2,3 ,π = {β ,π, 2 , 3 , 2,3 , {1,3}}
π πΌwgπ(π)={β ,X,{a},{c},{d},{a,c},{a,d},{c,d},{a,b,d},{a,c,d},{b,c,d}}, π πΌwgO(Y) = {β ,Y,{2},{3},{2,3},{1,3}},
π πΌπ(π )={{a},{d},{c},{a,c},{a,d},{c,d},{a,b,d},{a,c,d},{b,c,d}}. π πΌ O(Y)={{2},{3},{2,3},{1,3}}. The map π : π , π β π ,π is defined by f({a})={2}, f({b})={1},f({c})=3=f({d}).The function f is ( π πΌ wg)
*-quotient but not (π
πΌ)β-quotient
map. Since the set {1,3} is π πΌ -open in (Y,π ) but f-1
{1,3}={b,c,d} is not π πΌ -open in( X,π ).
Theorem 5.26: Every (π πΌπ€π )β-quotient map is strongly π πΌ wg-quotient.
Proof: Let V be an open set in (Y,π ). Then it is π πΌ wg-open in(Y,π ) since f is (π πΌπ€π )β-quotient map. f-1
(V) is π πΌ wg-
open in (X,π ).(Since f is π πΌ wg-irresolute). Also V is open in(Y,π ) implies f-1
(V) is π πΌ wg-open in (X,π ). since f is
(π πΌπ€π )β-open V is open in(Y,π ). Hence f is strongly π πΌ wg-quotient map.
Remark 5.27: Converse need not be true
Example 5.28: Let X={a,b,c,d}, π = β ,π , π , π , π , π , π , π , π , π = 1,2,3 ,π = {β ,π , 1 , 1,2 }
π πΌ wgπ(π )={β ,X,{a},{b},{a,b},{a,b,c},{a,b,d}}, π πΌ wgO(Y) = {β ,Y,{1},{1,2},{1,3}} Let π : π , π β π ,π is defined
by f({a})={1}, f({b})={2}=f({c}),f({d})={3}.The function f is strongly π πΌ wg-quotient but not a (π πΌπ€π )β-quotient. Since
the set {1,3} is π πΌ wg-open in(Y,π ) but f-1
{1,3}={a,d} is not open in (X,π ).
Remark 5.29: Quotient map and πΌ β-quotient map are independent
Example 5.30: Let X={a,b,c,d}, π = β ,π , π , π , π , π = 1,2,3 ,π = {β ,π , 1 , 1,2 }
πΌπ (π )={β ,X,{a},{a,b},{a,c},{a,d},{a,b,c},{a,b,d},{a,c,d}}, πΌO(Y) = {β ,Y,{1},{1,2},{1,3}} Let π : π , π β π ,π is
defined by f(a)=1, f(b)={2},f(c)=3=f(d).The function f is quotient but not a (πΌ )β-quotient. Since
f-1
{1,3}={a,c,d} is πΌ -open in(X,π ) but the set {1,3} is not open in (Y,π ).
Example 5.31: Let X={a,b,c,d}, π = β ,π , π , π , π , {π , π , π } , π = 1,2,3 ,π = {β ,π , 1 , 1,2 , {1,3}}
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πΌπ (π )={β ,X,{a},{a,b},{a,c},{a,d},{a,b,c},{a,b,d},{a,c,d}}, πΌO(Y) = {β ,Y,{1},{1,2},{1,3}} Let π : π , π β π ,π is
defined by f(a)=1, f(b)={2},f(c)=3=f(d).The function f is πΌ β quotient but not a quotient map. Since
f-1
{1,3}={a,c,d} is πΌ -open in(X,π ) but the set {1,3} is not open in (Y,π )
Remark 5.32: Quotient map and strongly π πΌ wg-quotient map are independent.
Example 5.33: X={a,b,c,d}, π = β ,π , π , π , π , π , π ,π ,π = 1,2,3 ,π = {β ,π , 2 , 3 , 2,3 , {1,3}}
π πΌ wgπ(π )={β ,X,{a},{c},{d},{a,c},{a,d},{c,d},{a,b,d},{a,c,d},{b,c,d}}, π πΌ wgO(Y) = {β ,Y,{2},{3},{2,3},{1,3}},
πΌπ (π )={{d},{a,c},{a,c,d}}, πΌ O(Y)={{2},{3},{2,3},{1,3}}. The map π : π , π β π ,π is defined by f(a)=2,
f(b)=1,f(c)=3=f(d).The function f is strongly π πΌ wg-quotient but not quotient map. Since the set {2} is open in (Y,π ) but f-
1{2}={a} is not open in( X,π ).
Example 5.34: X={a,b,c,d}, π = β ,π , π , π , π ,π = 1,2,3 ,π = {β ,π , 1 , 1,2 }
π πΌ wgπ(π )={β ,X,{a},{a,b},{a,c},{a,d},{a,b,c},{a,b,d},{a,c,d}}, π πΌ wgO(Y) = {β ,Y,{1},{1,2},{1,3}}, The map
π : π , π β π ,π is defined by f(a)=1, f(b)=2,f(c)=3=f(d).The function f is quotient but not strongly π πΌ wg-quotient map.
Since f-1
({1,3} is π πΌ wg -open in (X,π ) but the set {1,3} is not open in
(Y,π ).
Remark 5.35: From the above results we have the following diagram where A B represent A implies B but not
conversely, A B represents A and B are independent each other.
VI. Applications Theorem 6.1: The composition of two (π πΌπ€π )β-quotient maps is (π πΌπ€π )β-quotient.
Proof: Let π : π , π β π ,π and π : π ,π β (π , π ) be two (π πΌπ€π )β-quotient maps. Let V be any π πΌ wg-open set in
(Z,π ). Since g is (π πΌπ€π )β-quotient, g-1
(V) is π πΌ wg-open in(Y,π ) and since f is π πΌπ€π β-quotient then
(f-1
(g-1
(V)))= (gβf)-1
(V) is π πΌ wg-open in(X,π ). Hence gβf is π πΌ wg-irresolute.
Let (gβf)-1
(V) is π πΌ wg-open in(X,π ). Then f-1
(g-1
(V)) is π πΌ wg-open in(X,π ). Since f is (π πΌπ€π )β-quotient, g-1
(V)
is open in (Y,π ). Since g is (π πΌπ€π )β-quotient, V is open in (Z,π ). Hence gβf is (π πΌπ€π )β-quotient.
Proposition 6.2: If π : π , π β π ,π is π πΌ wg-quotient map and π : π , π β π , π is a continuous map that is constant
on each set h-1
(y) for yβY, then g induces a π πΌ wg-continuous map π : π ,π β π , π π π’π π π‘ π ππ‘ π β π = π . Proof: g is a constant on h
-1(y) for each yβY, the set g(h
-1(y)) is a one point set in (Z,π ). If f(y) denote this point, then it is
clear that f is well defined and for each π₯ β π , π π π₯ = π (π₯ ). We claim that f is π πΌ wg-continuous. For if we let V be
any open set in (Z,π ), then g-1
(V) is an open set in (X,π ) as g is continuous. But g-1
(V)=h-1
(f-1
(V)) is open in (X,π ). Since h
is π πΌ wg-quotient map, f-1
(V) is a π πΌ wg-open in(Y,π ). Hence f is π πΌ wg-continuous.
Proposition 6.3: If a map π : π , π β π ,π is surjective, π πΌ wg-continuous and π πΌ wg-open then f is a π πΌ wg-quotient
map.
Proof: To prove f is π πΌ wg-quotient map. We only need to prove f-1
(V) is open in (X,π ) implies V is π πΌ wg-open in (Y,π ).
Since f is π πΌ wg-continuous. Let f-1
(V) is open in (X,π ). Then f(f-1
(V)) is π πΌ wg-open set, since f is π πΌ wg-open. Hence V is
π πΌ wg-open set. Hence V is π πΌ wg-open set, as f is surjective, f(f-1
(V))=V. Thus f is a π πΌ wg-quotient map.
Proposition 6.4: If π : π , π β π ,π be open surjective, π πΌ wg-irresolute map, and π : π ,π β (π ,π )is a π πΌ wg-
quotient map then π β π : π , π β (π ,π ) is π πΌ wg-quotient map.
Proof: Let V be any open set in (Z, π ). Since g is π πΌ wg-quotient map then g-1
(V) is π πΌ wg-open in (Y,π ). Since f is π πΌ wg-
irresolute, f-1
(g-1
(V)) =(gβf)-1
(V) is π πΌ wg-open in (X,π ). This implies
(gβf)-1
(V) is π πΌ wg-open set in (X,π ). This shows that gβf is π πΌ wg-continuous map. Also assume that
π β π β1 π ππ ππππ ππ π , π .πΉππ π β π , π‘ π ππ‘ ππ (π β1 π β1 π ππ ππππ ππ π ,π . It follows that g-
1(V) is open in (Y,π ). Since f is surjective and g is π πΌ wg-quotient map. V is π πΌ wg-open set in(Z,π ).
Proposition 6.5: Let π : π , π β π ,π be strongly π πΌ wg-open surjective and π πΌ wg-irresolute map and π : π ,π β(π ,π ) be strongly π πΌ wg-quotient map then π β π is a strongly π πΌ wg-quotient map.
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Proof: Let V be an open set in(Z,π ). Since g is strongly π πΌ wg-quotient, g-1
(V) is a π πΌ wg-open in(Y,π ). Since f is π πΌ wg-
irresolute, f-1
(g-1
(V)) is a π πΌ wg-open in (X,π ) implies (g βf)-1
(V) is a π πΌ wg-open in (X,π ). Assume
(gβf)-1
(V) is π πΌ wg-open in(X,π ). Then (π β1 π β1 π ππ π πΌ wg-open in (X,π ). Since f is strongly π πΌ wg-open, then f(f-
1(g
-1(V))) is π πΌ wg-open in (Y,π ) which implies g
-1(V) is π πΌ wg-open in(Y,π ). Since g is strongly π πΌ wg-quotient map, V is
open in (Z,π ). Thus gβf is strongly π πΌ wg-quotient map.
Theorem 6.6: Let p:(X,π ) β π ,π be π πΌ wg-quotient map and the spaces (X,π ), (π ,π ) are π π πΌπ€π -spaces.
f:(Y,π )β(Z,π ) is a strongly π πΌ wg-continuous iff fβ π : π , π β π , π is a strongly π πΌ wg-continuous.
Proof: Let f be strongly π πΌ wg-continuous and U be any π πΌ wg-open set in (Z,π ). Then f-1
(U) is open in (Y,π ). Since p is
π πΌ wg-quotient map, then p-1
(f-1
(U))=(fβp)-1
(U) is π πΌ wg-open in(X,π ). Since(X,π ) is π π πΌπ€π -space,
p-1
(f-1
(U)) is open in (X,π ). Thus fβp is strongly π πΌ wg-continuous.
Conversely, Let the composite function fβp is strongly π πΌ wg-continuous. Let U be any π πΌ wg-open set in (Z,π ),
p-1
(f-1
(U)) is open in (X,π ). Since p is a π πΌ wg-quotient map, it implies that f-1
(U) is π πΌ wg-open in (Y,π ). Since (Y,π ) is a
π π πΌπ€π -space, f-1
(U) is open in (Y,π ). Hence f is strongly is π πΌ wg-continuous.
Theorem 6.7: Let π : π , π β π ,π be a surjective, strongly π πΌ wg-open and π πΌ wg-irresolute map and π : π ,π β(π ,π ) be a (π πΌπ€π )β-quotient map, then gβf is a (π πΌπ€π )β-quotient map.
Proof: Let V be π πΌ wg-open set in (Z,π ). Since g is a (π πΌπ€π )β-quotient map, g-1
(V) is a π πΌ wg-open set in(Y,π ), since f is
π πΌ wg-irresolute, f-1
(g-1
(V)) is π πΌ wg-open in (X,π ). Then (gβ π )-1
(V) is π πΌ wg-open in (X,π ). Since f is strongly π πΌ wg-
open, f(f-1
(g-1
(V))) is π πΌ wg-open in (Y,π ) which implies g-1
(V) is a π πΌ wg-open in (Y,π ). Since g is (π πΌπ€π )β-quotient
map then V is open in (Z,π ).
Hence gβf is a (π πΌπ€π )β-quotient map.
Theorem 6.8: Let π : π , π β π ,π be a strongly π πΌ wg-quotient map and π : π ,π β (π , π )be a (π πΌπ€π )β-quotient
map and f is π πΌ wg-irresolute then gβf is (π πΌπ€π )β-quotient map.
Proof: Let V be a π πΌ wg-open in (Z,π ). Then g-1
(V) is π πΌ wg-open in (Y,π ) since g is (π πΌπ€π )β-quotient map. Since f is
π πΌ wg-irresolute map, then f-1
(g-1
(V)) is π πΌ wg-open in (X,π ). ie, (gβf)-1
(V) is π πΌ wg-open in (X,π ) which shows that gβf is
π πΌ wg βirresolute. Let f-1
(g-1
(V)) is π πΌ wg-open in (X,π ). Since f is strongly π πΌ wg-quotient map then g-1
(V) is open in
(Y,π ) which implies g-1
(V) is π πΌ wg-open in(Y,π ). Since g is (π πΌπ€π )β-quotient map, V is open in (Z,π ). Hence gβf is
(π πΌπ€π )β-quotient map.
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