Some Common Fixed Point Results for Expansive Mappings in a Cone Metric Space

IOSR Journal of Mathematics (IOSR-JM)
e-ISSN: 2278-5728.Volume 6, Issue 1 (Mar. - Apr. 2013), PP 59-61
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Some Common Fixed Point Results for Expansive Mappings in a
Cone Metric Space
S.K. Tiwari*1
, R. P. Dubey1
, A. K. Dubey2
1
Department of Mathematics, Dr. C.V. Raman University, Bilaspur, Chhattisgarh, India-495113
2
Department of Mathmetics, Bhilai Institute of Technology Bhilai House, Durg India 491001
Abstract: The purpose of this work is to extend and generalize some common fixed point theorems for
Expansive type mappings in complete cone metric spaces. We are attempting to generalize the several well-
known recent results.
Mathematical subject classification; 54H25, 47H10
Key word: Complete cone metric space, common fixed point, expansive type mapping.
I. Introduction
Very recently, Huang and Zhang [3] introduced the concept of cone metric space by replacing the set of
real numbers by an ordered Banach space. They prove some fixed point Theorems for contractive mappings
using normality of the cone. The results in [3] were generalized by Sh. Rezapour and Hamlbarani [4] omitted
the assumption of normality on the cone, which is a milestone in cone metric space.
In this manuscript, the known results [14] are extended to cone metric spaces where the existence of
common fixed points for expansive type mappings on cone metric spaces is investigated.
II. Preliminary Notes
Definition 2.1[3] : Let E be a real Banach space and P, a subset of E. Then P is called a cone if and only if:
(i) P is closed, non-empty and P ≠ {0} ;
(ii) 𝑎, 𝑏 ϵ 𝑅, 𝑎,𝑏≥ 0 𝑥,𝑦 ϵ 𝑷 ⇒ 𝑎𝑥+𝑏𝑦 ϵ 𝑷;
(iii) 𝑥 ϵ P and – 𝑥 ϵ P => 𝑥 = 0.
Given a cone P⊆E, we define a Partial ordering ≤ on E with respect to P by 𝑥 ≤ 𝑦 if and only if 𝑦 - 𝑥 ϵ 𝑷. We
shall write x ≪ y to denote 𝑥 ≤ 𝑦 but 𝑥 ≠ 𝑦 to denote 𝑦 - 𝑥 ϵ p0
, where 𝑝0
stands for the interior of P.
Remark 2.2 [7]: λ𝑝0
⊆𝑝0
𝑓𝑜𝑟 λ> 0 and 𝑝0
+ 𝑝0
⊆ 𝑝0
Definition 2.2 [3] : Let X be a non-empty set and 𝑑 : 𝑋 × 𝑋 → 𝐸 a mapping such that
(𝑑1) 0 ≤ (𝑥 ,𝑦) for all𝑥,𝑦 ϵ 𝑋 and 𝑑 𝑥, 𝑦 = 0 if and only if 𝑥 = 𝑦,
(𝑑2) 𝑑 (𝑥, 𝑦) = 𝑑 (𝑦, 𝑥) for all 𝑥, 𝑦 𝜖 𝑋,
(𝑑3) 𝑑 (𝑥, 𝑦) ≤ 𝑑(𝑥, 𝑧) + 𝑑(𝑧, 𝑦) for all 𝑥, 𝑦, 𝑧 ϵ𝑋.
Then d is called a cone metric on 𝑋, and (𝑋, d) is called a cone metric space.
Example 2.4 [3]: Let 𝐸 = 𝑅2 ,
𝑃 𝑥 , 𝑦 𝜖 𝐸: 𝑥, 𝑦 ≥ 0 and 𝑋 = 𝑌, defined by 𝑑 𝑥 , 𝑦 = ( 𝛼| 𝑥 − 𝑦 |,
𝛽| 𝑥 − 𝑦 | , 𝛾| 𝑥 − 𝑦) where 𝛼, 𝛽, 𝛾 ≥0 is a constant. Then (𝑋, 𝑑) is a cone metric space.
Definition 2.5 [3]: Let (𝑋, 𝑑) be a cone metric space, 𝑥𝜖 𝑋 and {𝑥 𝒏} be a sequence in 𝑋. Then
𝑖 {𝑥 𝒏} 𝒏≥1 converges to 𝑥 whenever to every 𝑐 𝜖 𝐸 with 0 ≪ 𝑐 there is a natural number N such that
𝑑 𝑥 𝑛 , 𝑥 ≪ 𝑐 for all n ≥ N.
𝑖𝑖 {𝑥 𝒏} 𝒏≥1 is said to be a Cauchy sequence if for every 𝑐 ∊ 𝐸 with 0 ≪ 𝑐 there is a natural number N such
that 𝑑(𝑥 𝒏, 𝑥 𝑚) ≥ 𝑐 for all𝑛, 𝑚 ≥ 𝑁.
𝑖𝑖𝑖 (𝑋, 𝑑) is called a complete cone metric space if every Cauchy sequence in 𝑋 is convergent in 𝑋.
Definition 2.6[3]: Let(𝑋, 𝑑)𝑏𝑒 𝑎 𝑐𝑜𝑛𝑒 𝑚𝑒𝑡𝑟𝑖𝑐 𝑠𝑝𝑎𝑐𝑒, 𝑃 𝑏𝑒 𝑎 𝑐𝑜𝑛𝑒 𝑖𝑛 𝑟𝑒𝑎𝑙 𝐵𝑎𝑛𝑎𝑐ℎ 𝑠𝑝𝑎𝑐𝑒 𝐸, 𝑖𝑓
𝑖 𝑎 𝜖 P and 𝑎 ≪ 𝑐 for some 𝑘𝜖 0,1 then 𝑎 = 0.
𝑖𝑖 𝑎 𝜖 P and 𝑎 ≪ 𝑐 for some 𝑘𝜖 0,1 then 𝑎 = 0.
(iii)𝑢 ≤ 𝑣, 𝑣 ≪ 𝑤 , then 𝑢 ≪ 𝑤.

Some Common Fixed Point Results for Expansive Mappings in a Cone Metric Space
Lemma 2.7
𝐿𝑒𝑡 𝑥, 𝑑 𝑏𝑒 𝑎 𝑐𝑜𝑛𝑒 𝑚𝑒𝑡𝑟𝑖𝑐 𝑠𝑝𝑎𝑐𝑒 𝑎𝑛𝑑 𝛲 𝒃𝒆 𝑎 𝑐𝑜𝑛𝑒 𝑚𝑒𝑡𝑟𝑖𝑐 𝑠𝑝𝑎𝑐𝑒 𝑖𝑛 𝑟𝑒𝑎𝑙 𝐵𝑎𝑛𝑎𝑐ℎ 𝑠𝑝𝑎𝑐𝑒 𝐸 𝑎𝑛𝑑
𝛼1, 𝛼2, 𝛼3. 𝛼4 𝛼 ≥ 0. If 𝑥 𝒏 →𝑥, 𝑦 𝒏→ 𝑦, 𝑧 𝒏→z, and
an→ 𝑝 𝑖𝑛 𝑥 𝑎𝑛𝑑 𝛼1 𝑑 𝑥 𝑛, 𝑥 , +𝛼2 𝑑 𝑦𝑛, 𝑦 +𝛼3 𝑑 𝑧 𝑛, 𝑧 +. 𝛼4 𝑑 𝑝𝑛, 𝑝 . 𝑇ℎ𝑒𝑛 𝑎 = 0.
III. Main 𝐑𝐞𝐚𝐮𝐥𝐭:
Theorem 3.1 Let (𝑋 , 𝑑)be a complete cone metric space with respect to a cone Ρ containing in a real Banach
space𝐸. Let R1, R2 be any two surjective self mappings of 𝑋 satisfy
𝒅(𝑅1 𝑥, 𝑅2 y) ≥ α 𝑑(𝑥, 𝑅1 𝑥) + β 𝑑(𝑦, 𝑅2 𝑦) + γ 𝑑(𝑥, 𝑦)+ 𝑘[𝑑( 𝑥, 𝑅2 𝑦) + 𝑑(𝑦, 𝑅1 𝑥)]…… (3.1.1)
for each 𝑥,𝑦 ϵ 𝑋, 𝑥≠ 𝑦 where α ,β, γ, 𝑘 ≥ 0, α + β + γ >1+2𝑘, β + γ > k and γ >2k. Then 𝑅1 and 𝑅2 have a unique
common fixed point.
Proof: Let x0 be an arbitrary point in X. Since R1 and R2 surjective mappings, there exist points 𝑥1 ϵ 𝑅1
−1
𝑥0
and 𝑥2ϵ 𝑅2
−1
𝑥1 that is 𝑅1 𝑥1 = 𝑥0 and 𝑅2 𝑥2 = 𝑥1. In this way, we define the sequence 𝑥 𝑛 with
𝑥2𝑛+1ϵ𝑅1
−1
𝑥2𝑛 and 𝑥2𝑛+2ϵ 𝑅2
−1
𝑥2𝑛+1 .
i.e. 𝑥2𝑛 = 𝑅1 𝑥2𝑛+1 for n= 0,1 ,2,…………..(3.1.2)
𝑥2𝑛+1 = 𝑅2 𝑥2𝑛+2 for n =0,1,2……………(3.1.2)
Note that, if 𝑥2𝑛 = 𝑥2𝑛+1 for some n≥0, then 𝑥2𝑛 is fixed point of 𝑅1 and 𝑅2. Now putting x =𝑥2𝑛+1 and
𝑦 = 𝑥2𝑛+2 from 3.1.1 , we have
𝑑 𝑅1 𝑥2𝑛+1, 𝑅2 𝑥2𝑛+2 = 𝛼 𝑑 𝑥2𝑛+1, 𝑅1 𝑥2𝑛+1 + 𝛽 𝑑( 𝑥2𝑛+2, 𝑅2 𝑥2𝑛+2)+𝛾 𝑑 𝑥2𝑛+1, 𝑥2𝑛+2
+ 𝑘[𝑑 𝑥2𝑛+1, 𝑅2 𝑥2𝑛+2 + 𝑑 𝑥2𝑛+2, 𝑅2 𝑥2𝑛+1 ]
⇒ 𝑑(𝑥2𝑛 ,𝑥2𝑛+1) ≥ 𝛼 𝑑 𝑥2𝑛+1, 𝑥2𝑛 + 𝛽 𝑑( 𝑥2𝑛+2, 𝑥2𝑛+1)+𝛾 𝑑 𝑥2𝑛+1, 𝑥2𝑛+2
+ 𝑘[𝑑 𝑥2𝑛+1, 𝑥2𝑛+1 + 𝑑 𝑥2𝑛+2, 𝑥2𝑛 ]
⇒ 𝑑(𝑥2𝑛 , 𝑥2𝑛+1) ≥ 𝛼𝑑 𝑥2𝑛+1, 𝑥2𝑛 + 𝛽 𝑑( 𝑥2𝑛+2, 𝑥2𝑛+1)+𝛾𝑑 𝑥2𝑛+1, 𝑥2𝑛+2
+ 𝑘[𝑑 𝑥2𝑛+2, 𝑥2𝑛+1 + 𝑑 𝑥2𝑛+1, 𝑥2𝑛 ]
⇒ 𝑑(𝑥2𝑛 , 𝑥2𝑛+1) ≥ [𝛼+ 𝑘]𝑑 𝑥2𝑛+1, 𝑥2𝑛 + [𝛽 + 𝛾 + 𝑘]𝑑 𝑥2𝑛+1, 𝑥2𝑛+2
⇒ 𝑑 𝑥2𝑛+1, 𝑥2𝑛+2 ≤
1− 𝛼+ 𝑘
𝛽 +𝛾+𝑘
(𝑥2𝑛 , 𝑥2𝑛+1)………………..(3.1.4)
Where h =
1− 𝛼+ 𝑘
𝛽 +𝛾+𝑘
< 1 , [as α + β + γ >1+2k]
In general
𝑑(𝑥2𝑛 , 𝑥2𝑛+1)≤ ℎ 𝑑(𝑥2𝑛−1, 𝑥2𝑛 )
⇒ 𝑑(𝑥2𝑛 , 𝑥2𝑛+1)≤ ℎ2𝑛
(𝑥2𝑛−1, 𝑥2𝑛 )…………………..(3.1.5)
So for every positive integer p, we have
𝑑(𝑥2𝑛 , 𝑥2𝑛+𝑝) ≤ 𝑑 𝑥2𝑛, 𝑥2𝑛+1 +𝑑 𝑥2𝑛+1 𝑥2𝑛+2 +……….+ 𝑑 𝑥2𝑛+𝑝−1, 𝑥2𝑛+𝑝
≤ ( ℎ2𝑛
+ ℎ2𝑛+1
+…………+ ℎ2𝑛+𝑝−1
) 𝑑 𝑥0, 𝑥1
. = ℎ2𝑛
1 + ℎ + ℎ2
+ ⋯ … … … . +ℎ2𝑛+𝑝−1
𝑑 𝑥0, 𝑥1
<
ℎ2𝑛
1−ℎ
d 𝑥0, 𝑥1 …………………….. 3.1.6
Therefore 𝑥2𝑛 is a Cauchy sequence, which is complete space in X there exist 𝑥∗
ϵ 𝑋 such that𝑥2𝑛→ 𝑥∗
. Since
R1 is surjective map, there exist a point y in X such that
𝑦 ϵ 𝑅1
−1
𝑥∗
. i.e. 𝑥∗
= 𝑅1 𝑦 ………………………(3.1.7)
Now consider 𝑑 𝑥2𝑛,𝑥∗ = 𝑑 𝑅1 𝑥2𝑛+1, 𝑦
≥ 𝛼𝑑 𝑥2𝑛+1, 𝑅1 𝑥2𝑛+1 + 𝛽𝑑 𝑦, 𝑅1 𝑦 + 𝛾𝑑 𝑥2𝑛+1, 𝑦 + 𝑘 𝑑 𝑥2𝑛+1, 𝑅1 𝑦 +
𝑑 𝑦,𝑅1𝑥2𝑛+1
⇒𝑑 𝑥∗
, 𝑥∗
≥ 𝛼𝑑 𝑥∗
, 𝑥∗
+ 𝛽𝑑 𝑦, 𝑥∗
+ 𝛾𝑑 𝑥∗
, 𝑦 +
𝑘 𝑑 𝑥2𝑛+1, 𝑅1 𝑦 + 𝑑 𝑦, 𝑅1 𝑥2𝑛+1
⇒𝑑 𝑥∗
, 𝑥∗
≥ 𝛼𝑑 𝑥∗
, 𝑥∗
+ 𝛽𝑑 𝑦, 𝑥∗
+ 𝛾𝑑 𝑥∗
, 𝑦 + 𝑘 𝑑 𝑥2𝑛+1, 𝑅1 𝑦 + 𝑑 𝑦, 𝑅1 𝑥2𝑛+1
⇒ 0 ≥ 𝛽 + 𝛾 + 𝑘 d 𝑥∗
, 𝑦
⇒ 𝑑 𝑥∗
𝑦 = 0 , as 𝛽 + 𝛾 + 𝑘 > 0
⇒ 𝑥∗
= y……………………………………………………….. 3.1.8
Hence 𝑥∗
is a fixed point of 𝑅1. as 𝑅1 𝑦 = 𝑥∗
= 𝑦. Now if z be another fixed point of 𝑅1 ,
i.e. R1z = z. Then
(𝑥*, z) = 𝑑 (𝑅1 𝑥*, 𝑅1z)
≥ 𝛼𝑑(𝑅1 𝑥*, 𝑅1 𝑧) + 𝛽𝑑(𝑧, 𝑅1z) + 𝛾𝑑(𝑥*,𝑧) + 𝑘[𝑑(𝑥*,𝑧) +d (z, 𝑥*)]
=k [ 𝑑(𝑥*,𝑧) + ( 𝑧, 𝑥*)] +𝛾𝑑 (𝑥*,𝑧)(z, 𝑅1 𝑧)
= (2𝑘+𝛾) 𝑑(𝑥*, z)

Some Common Fixed Point Results for Expansive Mappings in a Cone Metric Space
⇒ 𝑑(𝑥*,𝑧) ≤
1
𝑐+2𝑘
𝑑(𝑥*,𝑧)
⇒ 𝑑(𝑥*,𝑧) = 0 as 𝑐 >2𝑘 as and by proposition 2.6 (i).
⇒ 𝑥* = 𝑧. Therefore 𝑅1 has a unique fixed point .Similarly it can be established that 𝑅2 𝑥* = 𝑥*. Hence 𝑅1 𝑥*
=𝑥*=𝑅2 𝑥*.Thus 𝑥* is the common fixed point of 𝑅1 and 𝑅2. These completed the proof of the theorem.
Corollary 3.2 Let (x, d) be a complete cone metric space with respect to a cone P containing in a real Banach
space 𝐸. Let R1and R2 be any two surjective self mappings of 𝑋 satisfying
𝑑(𝑅1 𝑥, 𝑅2 y) ≥ α𝑑(x , 𝑅1 𝑥)+ β 𝑑(y,𝑅2y)+ γ𝑑(𝑥 ,𝑦) ……..(3.1.9)
For each , ϵ 𝑋 , 𝑥≠ 𝑦 where 𝛼, 𝛽, 𝛾, ≥ 0, 𝛼 + 𝛽 + 𝛾 >1. Then 𝑅1 and 𝑅2 have a unique fixed point.
Proof: The proof of the corollary immediately follows by putting 𝑘 = o in the previous theorem.
Corollary 3.3 Let (x, d) be a complete cone metric space with respect to a cone p containing in a real Banach
space 𝐸. Let R1and R2 be any two surjective self mappings of 𝑋 satisfying
𝑑(𝑅1 𝑥, 𝑅2 y) ≥𝑘[𝑑( 𝑥, 𝑅2 𝑦) + 𝑑(𝑦, 𝑅1 𝑥)] For each 𝑥, ϵ𝑋 , 𝑥 ≠ 𝑦 where 𝑘≥0
Then 𝑅1 and 𝑅2 have a unique fixed point.
Proof: The proof of the corollary immediately follows by putting 𝛼 = 0, 𝛽 = 0 𝑎𝑛𝑑 𝛾 = 0 in the previous
theorem.
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