Keywords: fixed point theorems, symmetric spaces, g-reciprocal continuity, noncompatible mappings, g-compatible
American Journal of Mathematical Analysis, 2013 1 (3),
pp 39-41.
DOI: 10.12691/ajma-1-3-3
Received August 22, 2013; Revised September 13, 2013; Accepted September 29, 2013
Copyright © 2013 Science and Education Publishing. All Rights Reserved.
1. Introduction
Fixed point theory of strict contractive conditions constitutes a very important class of mappings and includes contraction mappings as their subclass. It may be observed that strict contractive conditions do not ensure the existence of common fixed points unless some strong condition is assumed either on the space or on the mappings. In such cases either the space is taken to be compact or some sequence of iterates is assumed to be Cauchy sequence. The study of common fixed points of strict contractive conditions using noncompatibility was initiated by Pant [9]. Motivated by Pant [9] researchers [1, 3, 6, 7, 11, 12, 13] of this domain obtained common fixed point results for strict contractive conditions under generalized metric spaces. The significance of this paper lies in the fact that we can obtain fixed point theorems for g-reciprocally continuous mappings in generalized strict contractive conditions without assuming any strong conditions on the space or on the mappings.
2. Preliminaries
Definition 2.1 [14]. Let X be a non-empty set. A symmetric on a set X is a real valued function
such that,
Let d be a symmetric on a set X and for
and any x
, let B(x,
. A topology t(d) on X is given by U
if and only if for each x
for some
.A symmetric d is a semi-metric if for each x
and each
,
is a neighborhood of x in the topology t(d). There are several concepts of completeness in this setting. A sequence is a d-Cauchy if it satisfies the usual metric condition.
Definition 2.2. [14]. Let (X, d) be a symmetric (semi-metric) space.
(1). (X, d) is S-Complete if for every d-Cauchy sequence {xn } there exists x in X with lim
.
(2). (X, d) is d-Cauchy Complete if for every d-Cauchy sequence {xn} there exists x in X with lim xn = x with respect to t(d).
(3).
is d-Continuous if
implies 
(4).
is t(d) continuous if
with respect to t(d) implies
with respect to t(d).
The following two axioms were given by Wilson [14].
Definition 2.3. Let (X, d) be a symmetric (semi-metric) space.
W1: Given {xn}, x and y in X,
and
.
W2: Given {xn}, {yn} and an x in X,
and
.
Definition 2.4. [4]. Two self maps
and g of a metric space
are called compatible if
whenever
is a sequence in
such that
for some
in 
The definition of compatibility implies that the mappings
and
will be noncompatible if there exists a sequence
in
such that
for some
in
but
is either non zero or nonexistent.
Definition 2.5. [1]. Two self maps
and
of a metric space
are said to satisfy property (E. A.) if there exists a sequence
in
such that
for some
in
.
Definition 2.6 .[5] Two self maps
and
of a metric space
are called g-compatible if
whenever
is a sequence in
such that
for some
in 
Definition 2.7 [8]. Two selfmappings
and
of a metric space
are called reciprocally continuous iff
and
whenever
is a sequence such that
for some
in
Definition 2.8 [10]. Two selfmappings
and
of a metric space
are called g-reciprocally continuous iff
and
whenever
is a sequence such that
for some
in 
It may be observed that if
and
are both continuous then they are obviously g-reciprocally continuous but the converse is not true. It may also be observed that g-reciprocal continuity is independent of the notion of reciprocal continuity. The following examples illustrate this fact.
Example 2.1. [9]. Let
and
be the symmetric (semi-metric)
on
Define
as follows
Then
and
are g-reciprocally continuous but not reciprocally continuous. To see this let us consider the sequence
Then
and
Thus
and
are g-reciprocally continuous but they are not reciprocally continuous.
Example 2.2. [9]. Let
and
be symmetric (semi-metric)
on
Define
as follows
Then
and
are reciprocally continuous but not g-reciprocally continuous . To see this let us consider the sequence
Then
and
Thus
and
are reciprocally continuous but they are not g-reciprocally continuous.
Examples 2.1 and 2.2 clearly show that reciprocal continuity and g-reciprocally continuous reciprocal continuity are independent of each other.
3. Main Results
Theorem 3.1. Let
and
be g-reciprocally continuous self mappings of a symmetric space
satisfying
whenever the right hand side is nonzero. Suppose
and
satisfy property (E. A.). If
and
are g-compatible then
and
have a unique common fixed point.
Proof: Since
and
satisfy property (E. A.), there exists a sequence
in
such that
for some
in
Suppose that
and
are g- compatible. Then
g- reciprocally continuity of
and
implies that
and
The last two limits together imply
Since g- compatibility implies commutativity at coincidence points, i.e.,
and, hence 
If
then by using (i), we get
a contradiction. Hence
and
is a common fixed point of
and
This completes the proof of the theorem.
The next example illustrates the above theorem.
Example 3.1. Let
with the symmetric (semi-metric)
. Define
as follows
Then
and
satisfy all the conditions of Theorem 3.1 and have a unique common fixed point at
It can be verified in this example that
and
satisfy the contraction condition (i). Furthermore,
and
are g-reciprocally continuous g-compatible mappings. It is also obvious that
and
are not reciprocally continuous. Here
and
are not reciprocally continuous mappings.
Remark: In the above result we have not assumed strong conditions, e.g., completeness of the space, containment of the ranges of the mappings, closedness of the range of any one of the involved mappings and continuity of any mapping. We also proved a result using generalized strict contractive condition. It may be observed that strict contractive conditions do not ensure the existence of common fixed points unless the space is assumed compact or the strict contractive condition is replaced by some strong conditions, e.g., a Banach type contractive condition or a
contractive condition or a Meir-Keeler type contractive condition. In the result established in this paper, we have not assumed any mapping to be continuous. Thus we provide more answers to the problem posed by Rhoades [2] regarding existence a contractive definition which is strong enough to generate a fixed point, but which does not force the map to be continuous at the fixed point.
References
[1] | A. Aamri and D. El Moutawakil, Some new common fixed point theorems under strict contractive conditions, J. Math. Anal. Appl., 270 (2002), 181-188. |
| In article | CrossRef |
|
[2] | B. E. Rhoades, Contractive definitions and continuity, Contemporary Math. (Amer. Math. Soc.) 72 (1988), 233-245. |
| In article | |
|
[3] | Fang Jin-xuan and Gao Yang, Common fixed point theorems under strict contractive conditions in Menger spaces, Nonlinear Analysis 70 (2009), 184-193. |
| In article | CrossRef |
|
[4] | G. Jungck, Compatible mappings and common fixed points, Internat. J. Math. Math. Sci., 9(1986), 771-779. |
| In article | CrossRef |
|
[5] | H. K. Pathak and M. S. Khan, A comparison of various types of compatible maps and common fixed points, Indian J. Pure Appl. Math. 28 no. 4, (1997), 477-485. |
| In article | |
|
[6] | I. Kubiaczyk and S. Sharma, Some common fixed point theorems in Menger space under strict contractive conditions, Southeast Asian Bull. Math., 32(2008), 117-124. |
| In article | |
|
[7] | M. Imdad, Javid Ali and Ladlay Khan, Coincidence fixed points in symmetric spaces under strict contractions, J. Math. Anal. Appl., 320 (2006), 352-360. |
| In article | CrossRef |
|
[8] | R. P. Pant, Common fixed points of four mappings, Bull. Cal. Math. Soc. 90(1998), 281-286. |
| In article | |
|
[9] | R. P. Pant, Discontinuity and fixed points, J. Math. Anal. Appl. 240 (1999), 284-289. |
| In article | CrossRef |
|
[10] | R. P. Pant and R. K. Bisht, Common fixed points of pseudo compatible mappings, Revista de la Real Academia de Ciencias Exactas, Físicas y Naturales. Serie A. Matemáticas. |
| In article | |
|
[11] | R. P. Pant and V. Pant, Common fixed points under strict contractive conditions, J. Math. Anal. Appl., 248 (2000), 327-332. |
| In article | CrossRef |
|
[12] | R. K. Bisht, Common fixed points of generalized Meir-Keeler type condition and nonexpansive mappings; The International Journal of Mathematics and Mathematical Sciences, Volume 2012, Article ID 786814, 12 pages. |
| In article | |
|
[13] | R.U.Joshi, et.al, Common Fixed Points under Strict Contractive Condition and g-reciprocal Continuity, Journal of International Academy of Physical Sciences, Vol. 16 No.1 (2012). |
| In article | |
|
[14] | W.A.Wilson, on semi-metric spaces, Amer.J.Math, 53(1931), 361-373. |
| In article | CrossRef |
|