• Views 967
• Citations 3
• ePub 15
• PDF 437
`The Scientific World JournalVolume 2014, Article ID 134534, 6 pageshttp://dx.doi.org/10.1155/2014/134534`
Research Article

## Spaces of Ideal Convergent Sequences

1Department of Mathematics, Aligarh Muslim University, Aligarh 202002, India
2Department of Mathematics, Model Institute of Engineering & Technology, Kot Bhalwal, J&K 181122, India

Received 20 August 2013; Accepted 26 November 2013; Published 28 January 2014

Academic Editors: F. Başar and J. Xu

Copyright © 2014 M. Mursaleen and Sunil K. Sharma. 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.

#### Abstract

In the present paper, we introduce some sequence spaces using ideal convergence and Musielak-Orlicz function . We also examine some topological properties of the resulting sequence spaces.

#### 1. Introduction and Preliminaries

The notion of ideal convergence was first introduced by Kostyrko et al.  as a generalization of statistical convergence which was further studied in topological spaces by Das et al. see . More applications of ideals can be seen in [2, 3]. We continue in this direction and introduce -convergence of generalized sequences with respect to Musielak-Orlicz function.

A family of subsets of a nonempty set is said to be an ideal in if(1),(2) imply ,(3), imply ,while an admissible ideal of further satisfies for each ; see . A sequence in is said to be -convergent to . If for each , the set belongs to ; see . For more details about ideal convergent sequence spaces, see  and references therein.

Mursaleen and Noman  introduced the notion of -convergent and -bounded sequences as follows.

Let be a strictly increasing sequence of positive real numbers tending to infinity; that is, The sequence is -convergent to the number , called the -limit of , if , as , where

The sequence is -bounded if . It is well known  that if in the ordinary sense of convergence, then

This implies that which yields that and hence is -convergent to .

Let be a linear metric space. A function is called paranorm if(1), for all ,(2), for all ,(3), for all ,(4)if is a sequence of scalars with as and is a sequence of vectors with as , then as .

A paranorm for which implies that is called total paranorm and the pair is called a total paranormed space. It is well known that the metric of any linear metric space is given by some total paranorm (see [12, Theorem 10.4.2, P-183]). For more details about sequence spaces, see  and references therein.

An Orlicz function is a function which is continuous, nondecreasing, and convex with , for and as .

Lindenstrauss and Tzafriri  used the idea of Orlicz function to define the following sequence space. Let be the space of all real or complex sequences . Then, which is called an Orlicz sequence space. The space is a Banach space with the norm

It is shown in  that every Orlicz sequence space contains a subspace isomorphic to . The -condition is equivalent to for all values of and for .

A sequence of Orlicz function is called a Musielak-Orlicz function see; [17, 18]. A sequence defined by is called the complementary function of a Musielak-Orlicz function . For a given Musielak-Orlicz function , the Musielak-Orlicz sequence space and its subspace are defined as follows: where is a convex modular defined by

We consider equipped with the Luxemburg norm or equipped with the Orlicz norm

Let be a Musielak-Orlicz function and let be a bounded sequence of positive real numbers. We define the following sequence spaces:

We can write

If we take , for all , we have

The following inequality will be used throughout the paper. If , , then for all , and . Also for all .

The main aim of this paper is to study some ideal convergent sequence spaces defined by a Musielak-Orlicz function . We also make an effort to study some topological properties and prove some inclusion relations between these spaces.

#### 2. Main Results

Theorem 1. Let be a Musielak-Orlicz function and let be a bounded sequence of positive real numbers. Then, the spaces , , , and are linear.

Proof. Let and let , be scalars. Then, there exist positive numbers and such that
For a given , we have
Let . Since is nondecreasing convex function, so by using inequality (15), we have
Now, by (17), we have
Therefore, . Hence is a linear space. Similarly, we can prove that , , and are linear spaces.

Theorem 2. Let be a Musielak-Orlicz function. Then,

Proof. Let . Then, there exist and such that
We have
Taking supremum over on both sides, we get . The inclusion is obvious. Thus,
This completes the proof of the theorem.

Theorem 3. Let be a Musielak-Orlicz function and let be a bounded sequence of positive real numbers. Then, is a paranormed space with paranorm defined by

Proof. It is clear that . Since , we get . Let us take . Let
Let and . If , then we have
Thus, and
Let , where and let as . We have to show that as . Let
If and , then we observe that
From the above inequality, it follows that and, consequently,
This completes the proof.

Theorem 4. Let and be Musielak-Orlicz functions that satisfy the -condition. Then,
(i),
(ii) for .

Proof. (i) Let . Then, there exists such that
Let and choose with such that for . Write and consider
Since satisfies -condition, we have
For , we have
Since is nondecreasing and convex, it follows that
Since satisfies -condition, we have
Hence, From (32), (34), and (38), we have . Thus, . Similarly, we can prove the other cases.
(ii) Let . Then, there exists such that
The rest of the proof follows from the following equality:

Corollary 5. Let be a Musielak-Orlicz function which satisfies -condition. Then, holds for , and .

Proof. The proof follows from Theorem 3 by putting and .

Theorem 6. The spaces and are solid.

Proof. We will prove for the space . Let . Then, there exists such that
Let be a sequence of scalars with . Then, the result follows from the following inequality: and this completes the proof. Similarly, we can prove for the space .

Corollary 7. The spaces and are monotone.

Proof. It is easy to prove, so we omit the details.

Theorem 8. The spaces and are sequence algebra.

Proof. Let . Then,
Let . Then, we can show that
Thus, . Hence, is a sequence algebra. Similarly, we can prove that is a sequence algebra.

#### Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

#### References

1. P. Kostyrko, T. Šalát, and W. Wilczyński, “$I$-convergence,” Real Analysis Exchange, vol. 26, no. 2, pp. 669–685, 2000.
2. P. Das, P. Kostyrko, W. Wilczyński, and P. Malik, “$I$ and ${I}^{*}$-convergence of double sequences,” Mathematica Slovaca, vol. 58, no. 5, pp. 605–620, 2008.
3. P. Das and P. Malik, “On the statistical and $I$ variation of double sequences,” Real Analysis Exchange, vol. 33, no. 2, pp. 351–363, 2008.
4. V. Kumar, “On $I$ and ${I}^{*}$-convergence of double sequences,” Mathematical Communications, vol. 12, no. 2, pp. 171–181, 2007.
5. M. Mursaleen and A. Alotaibi, “On $I$-convergence in random 2-normed spaces,” Mathematica Slovaca, vol. 61, no. 6, pp. 933–940, 2011.
6. M. Mursaleen, S. A. Mohiuddine, and O. H. H. Edely, “On the ideal convergence of double sequences in intuitionistic fuzzy normed spaces,” Computers & Mathematics with Applications, vol. 59, no. 2, pp. 603–611, 2010.
7. M. Mursaleen and S. A. Mohiuddine, “On ideal convergence of double sequences in probabilistic normed spaces,” Mathematical Reports, vol. 12(62), no. 4, pp. 359–371, 2010.
8. M. Mursaleen and S. A. Mohiuddine, “On ideal convergence in probabilistic normed spaces,” Mathematica Slovaca, vol. 62, no. 1, pp. 49–62, 2012.
9. A. Şahiner, M. Gürdal, S. Saltan, and H. Gunawan, “Ideal convergence in 2-normed spaces,” Taiwanese Journal of Mathematics, vol. 11, no. 5, pp. 1477–1484, 2007.
10. B. C. Tripathy and B. Hazarika, “Some $I$-convergent sequence spaces defined by Orlicz functions,” Acta Mathematicae Applicatae Sinica, vol. 27, no. 1, pp. 149–154, 2011.
11. M. Mursaleen and A. K. Noman, “On some new sequence spaces of non-absolute type related to the spaces ${\ell }_{p}$ and ${\ell }_{\infty }$ I,” Filomat, vol. 25, no. 2, pp. 33–51, 2011.
12. A. Wilansky, Summability through Functional Analysis, vol. 85 of North-Holland Mathematics Studies, North-Holland Publishing, Amsterdam, The Netherlands, 1984.
13. K. Raj and S. K. Sharma, “Some sequence spaces in 2-normed spaces defined by Musielak-Orlicz function,” Acta Universitatis Sapientiae, vol. 3, no. 1, pp. 97–109, 2011.
14. K. Raj and S. K. Sharma, “Some generalized difference double sequence spaces defined by a sequence of Orlicz-functions,” Cubo, vol. 14, no. 3, pp. 167–190, 2012.
15. K. Raj and S. K. Sharma, “Some multiplier sequence spaces defined by a Musielak-Orlicz function in $n$-normed spaces,” New Zealand Journal of Mathematics, vol. 42, pp. 45–56, 2012.
16. J. Lindenstrauss and L. Tzafriri, “On Orlicz sequence spaces,” Israel Journal of Mathematics, vol. 10, pp. 379–390, 1971.
17. L. Maligranda, Orlicz Spaces and Interpolation, vol. 5 of Seminars in Mathematics, Polish Academy of Science, 1989.
18. J. Musielak, Orlicz Spaces and Modular Spaces, vol. 1034 of Lecture Notes in Mathematics, Springer, 1983.