Abstract
In a joint paper with Srivastava and Chopra, we introduced far-reaching generalizations of the extended Gammafunction, extended Beta function and the extended Gauss hypergeometric function. In this present paper, we extend the generalized Mittag–Leffler function by means of the extended Beta function. We then systematically investigate several properties of the extended Mittag–Leffler function, including, for example, certain basic properties, Laplace transform, Mellin transform and Euler-Beta transform. Further, certain properties of the Riemann–Liouville fractional integrals and derivatives associated with the extended Mittag–Leffler function are investigated. Some interesting special cases of our main results are also pointed out.
Keywords:
extended Beta function; extended hypergeometric functions; extended confluent hypergeometric function; Mittag–Leffler function; generalized Mittag–Leffler function; Laplace transform; Mellin transform; Euler-Beta transforms; Wright hypergeometric function; Fox H-function; fractional calculus operators MSC classifications:
Primary 26A33, 33E12, 33C05, 33C15, 33C20; Secondary 33C65, 33C90.
1. Introduction, Definitions and Preliminaries
Several interesting generalizations of the familiar Euler-Gamma function , Euler-Beta function , the Gauss hypergeometric functions and the generalized hypergeometric functions with r numerator and s denominator were studied and investigated by various authors (see, for example, [1,2,3,4,5,6,7] and the references cited in each of these papers). For example, for an appropriately-bounded sequence of arbitrary (real or complex) numbers, Srivastava et al. [8] (p. 243, Equation (2.1)) recently considered the function:
for some suitable constants and ω depending essentially on the sequence . In terms of the function defined by Equation (1), in a joint paper with Srivastava and Chopra [8], we introduced far-reaching generalizations of the extended Gamma function, extended Beta function and the extended Gauss hypergeometric function by:
and:
respectively, provided that the defining integrals in the definitions (Equations (2)–(4)) exist.
For various special choices of the sequence , the definition in Equations (2)–(4) would reduce to (known or new) extensions of the Gamma, Beta and hypergeometric functions. In particular, if we set:
the definition (Equations (2)–(4)) immediately reduces to the extended Gamma function , the extended Beta function and the extended hypergeometric function introduced by Özergin et al. [7]:
and:
respectively. Furthermore, for the sequence:
the definition (Equations (2)–(4)) reduces immediately to the generalized gammafunction, extended betafunction and extended Gauss hypergeometric function studied earlier by Chaudhry and Zubair [3] (p. 9, Equation (1.66)), Chaudhry et al. [1] and Chaudhry et al. [2]:
and:
respectively. For or (alternatively) for:
the definitions (Equations (2)–(4)) would reduce immediately to classical Gamma, Beta and Gauss hypergeometric functions (see, for details, [9,10]), respectively.
The one-parameter Mittag–Leffler function:
and its two-parameter extension, nowadays called the Mittag–Leffler function:
were introduced and studied by Mittag–Leffler [11,12], Wiman [13,14], Agarwal [15], Humbert [16] and Humbert and Agarwal [17].
In 1971, Prabhakar [18] introduced the three-parameter generalization of Equation (14) as:
called usually the Prabhakar function. Further, various authors studied and investigated generalized Mittag–Leffler functions (see, for details, [19,20,21,22,23,24,25]). Motivated essentially by the demonstrated potential for applications of these extended hypergeometric functions, we extend the generalized Mittag–Leffler function (Equation (15)) by means of the extended Beta function defined by Equation (3) and investigate certain basic properties, including differentiation formulas and the integral property, Laplace transform, Euler-Beta transform and Mellin transform with their several special cases and relationships with generalized hypergeometric function and H-function. Further, certain relations between the extended generalized Mittag–Leffler function and the Riemann–Liouville fractional integrals and derivatives are investigated. Some interesting special cases of our main results are also considered.
2. A Class of Extended Mittag–Leffler Functions
In terms of the extended Beta function defined by Equation (3), we propose a different extension of the generalized Mittag–Leffler function by replacing:
in Equation (15) as follows:
Remark 1. The special case of Equation (16) when we set the sequence , yields another form of the extended generalized Mittag–Leffler function:
Again, the sequence yields the known definition of Özarslan and Yilmaz [26] (with c = 1):
For or (alternatively) for , this immediately reduces to Prabhakar’s definition (Equation (15)).
3. Basic Properties of
In this section, we obtain certain basic properties, including the differentiation formula and the integral property of the extended generalized Mittag–Leffler function in Equation (16).
Theorem 1. The following differentiation formula for the extended generalized Mittag–Leffler function in Equation (16) holds true:
In particular, we have:
Proof. Using the definition (Equation (16)) in right-hand side of Equation (19), we have:
The relation Equation (20) follows from Equation (19) when or for . ☐
Theorem 2. The following derivative formulas for the extended generalized Mittag–Leffler function in Equation (16) are satisfied:
where ; ; .
In particular, we have:
Proof. Using Equation (16) and employing term-wise differentiation m times on the left-hand side of Equation (21) under the summation sign, which is possible in accordance with the uniform convergence of the series in Equation (16), we get:
The special cases of Equation (21) when or for are easily seen to yield Equation (22).
Corollary 1. The following integral property for the extended generalized Mittag–Leffler function in Equation (16) holds true:
where ; ; .
In particular, we have:
4. Integral Transforms of
In this section, we obtain the Laplace transform, Mellin transform representations and the Euler-Beta transform, alternatively called the Erdélyi–Kober fractional integral for the extended generalized Mittag–Leffler function , in Equation (16) as follows.
4.1. Laplace Transform
The Laplace transform (see, e.g., [27]) of the function is defined, as usual, by:
Theorem 3. The following Laplace transform representation for the extended generalized Mittag–Leffler function in Equation (16) holds true:
Now, using the definition (Equation (12)) to express the involved sum as an extended hypergeometric function, we are led to the desired result. ☐
Remark 3. The special case of Equation (26) when or for is seen to yield the known Laplace transform of the generalized Mittag–Leffler function (see [18] (p. 8, Equation (2.5)); see also [23] (p. 37, Equation (2.19))):
4.2. Mellin Transform
The Mellin transform [27] of a suitably-integrable function with index s is defined, as usual, by:
whenever the improper integral in Equation (27) exists.
Theorem 4. The following Mellin transform representation for the extended generalized Mittag–Leffler function in Equation (16) holds true:
where is the specialized case in Equation (2) for .
Upon interchanging the order of integration and summation in Equation (29), which can easily be justified by uniform convergence under the constraints stated with Equation (28), we get:
Using the easily-derivable result as in Section 4 of Srivastava et al. [8] (p. 251, Theorem 5):
we obtain:
Using the definition of the Wright generalized hypergeometric function (see, e.g., [28,29]) in Equation (32), we get the desired representation Equation (28). ☐
Corollary 2. The following Mellin transform representation is expressed in terms of generalized hypergeometric functions in Equation (28) as follows:
where and is an array of α parameters .
Remark 4. The Wright generalized hypergeometric function (see, e.g., [28,29]) is expressible in terms of Fox H-function (see, e.g., [30,31,32]) as follows (see, e.g., [32] (p. 25, Equation (1.140)) and [31] (p. 11, Equation (1.7.8)):
Now, applying the relationship Equation (34) to Equation (28), we can deduce an interesting representation for the extended Mittag–Leffler function in Equation (16) asserted by Corollary 3 below. We state here the resulting representation without proof.
Corollary 3. The following Mellin transform representations is expressed in terms of Fox H-functions in Equation (28) as follows:
4.3. Euler-Beta Transform
The Euler-Beta transform [27], alternatively called the Erdélyi–Kober fractional integral of the function , is defined, as usual, by:
Theorem 5. The following Euler-Beta transform or Erdélyi–Kober fractional integral representation for the extended generalized Mittag–Leffler function in Equation (16) holds true:
Proof. Using the definition (Equation (36)) of the Euler-Beta transform, we find from Equation (16):
Upon interchanging the order of integration and summation in Equation (38), which can easily be justified by uniform convergence under the constraint state with Equation (37), we get:
Using the definition (Equation (16)), we get the desired representation Equation (37). ☐
Corollary 4. In a similar manner, we obtain:
In general, we have:
5. Fractional Calculus Operators of
In this section, we derive certain interesting properties of the extended generalized Mittag–Leffler function in Equation (16) associated with right-sided Riemann–Liouville fractional integral operator and the right-sided Riemann-Liouville fractional derivative operator , which are defined as (see, e.g., [33,34]):
and:
where means the greatest integer not exceeding real x.
A generalization of Riemann–Liouville fractional derivative operator in Equation (42) by introducing a right-sided Riemann–Liouville fractional derivative operator of order and type with respect to x by Hilfer (see, e.g., [35]) is as follows:
The generalization Equation (43) yields the classical Riemann–Liouville fractional derivative operator when .
Theorem 6. Let . Then, for , the relation holds:
and
Proof. By virtue of the formulas (Equation (41) and Equation (16)), the term-by-term fractional integration and the application of the relation [34]:
yield for :
Next, by Equation (42) and Equation (16), we find that:
Applying Equation (21), we are led to the desired result Equation (45).
Using the known relation of Srivastava and Tomovski [36] (p. 203, Equation (2.18)):
in Equation (50), we are led to the desired result Equation (46).
Remark 4. The special cases of the results presented here when or for would reduce to the corresponding well-known results for the generalized Mittag–Leffler function (see, for details, [18] and [23]).
Acknowledgments
The author would like to express his deep gratitude for the reviewers’s suggestions for future works and helpful comments to improve this paper in the present form.
Conflicts of Interest
The author declares no conflict of interest.
References
- Chaudhry, M.A.; Qadir, A.; Raflque, M.; Zubair, S.M. Extension of Euler’s Beta function. J. Comput. Appl. Math. 1997, 78, 19–32. [Google Scholar] [CrossRef]
- Chaudhry, M.A.; Qadir, A.; Srivastava, H.M.; Paris, R.B. Extended hypergeometric and confluent hypergeometric functions. Appl. Math. Comput. 2004, 159, 589–602. [Google Scholar] [CrossRef]
- Chaudhry, M.A.; Zubair, S.M. Generalized incomplete gamma functions with applications. J. Comput. Appl. Math. 1994, 55, 99–124. [Google Scholar] [CrossRef]
- Chaudhry, M.A.; Zubair, S.M. On a Class of Incomplete Gamma Functions with Applications; Chapman and Hall (CRC Press Company): Boca Raton, FL, USA; London, UK; New York, NY, USA; Washington, DC, USA, 2002. [Google Scholar]
- Luo, M.; Raina, R.K. Extended generalized hypergeometric functions and their applications. Bull. Math. Anal. Appl. 2013, 5, 65–77. [Google Scholar]
- Özarslan, M.A.; Özergin, E. Some generating relations for extended hypergeometric function via generalized fractional derivative operator. Math. Comput. Model. 2010, 52, 1825–1833. [Google Scholar] [CrossRef]
- Özergin, E.; Özarslan, M.A.; Altın, A. Extension of gamma, beta and hypergeometric functions. J. Comput. Appl. Math. 2011, 235, 4601–4610. [Google Scholar] [CrossRef]
- Srivastava, H.M.; Parmar, R.K.; Chopra, P. A Class of Extended Fractional Derivative Operators and Associated Generating Relations Involving Hypergeometric Functions. Axioms 2012, 1, 238–258. [Google Scholar] [CrossRef]
- Rainville, E.D. Special Functions, 2nd ed.; Chelsea Publishing Company: Bronx, New York, NY, USA, 1971. [Google Scholar]
- Srivastava, H.M.; Karlsson, P.W. Multiple Gaussian Hypergeometric Series; Halsted Press: Chichester, UK; John Wiley and Sons: New York, NY, USA; Chichester, UK; Brisbane, Australia; Toronto, AB, Canada, 1985. [Google Scholar]
- Mittag-Leffler, G.M. Sur la nouvelle fonction Eα(x). C. R. Acad. Sci. Paris 1903, 137, 554–558. [Google Scholar]
- Mittag-Leffler, G.M. Sur la representation analytiqui d’une fonction monogene (cinquieme note). Acta Math. 1905, 29, 101–181. [Google Scholar] [CrossRef]
- Wiman, A. Über den fundamental satz in der theorie der functionen Eα(x). Acta Math. 1905, 29, 191–201. [Google Scholar] [CrossRef]
- Wiman, A. Über die nullstellun der funktionen Eα(x). Acta Math. 1905, 29, 217–234. [Google Scholar] [CrossRef]
- Agarwal, R.P. A propos d’une Note M. Pierre Humbert. C. R. Acad. Sci. Paris 1953, 236, 2031–2032. [Google Scholar]
- Humbert, P. Quelques resultats d’le fonction de Mittag-Leffler. C. R. Acad. Sci. Paris 1953, 236, 1467–1468. [Google Scholar]
- Humbert, P.; Agarwal, R.P. Sur la fonction de Mittag-Leffler et quelques unes de ses generalizations. Bull. Sci. Math. 1953, 77, 180–185. [Google Scholar]
- Prabhakar, T.R. A singular integral equation with a generalized Mittag-Leffler function in the kernel. Yokohama Math. J. 1971, 19, 7–15. [Google Scholar]
- Gorenflo, R.; Kilbas, A.A.; Rogosin, S.V. On the generalized Mittag-Leffler type functions. Integr. Transf. Spec. Funct. 1998, 7, 215–224. [Google Scholar] [CrossRef]
- Haubold, H.J.; Mathai, A.M.; Saxena, R.K. Mittag-Leffler function and their applications. J. Appl. Math. 2011. [Google Scholar] [CrossRef]
- Kilbas, A.A.; Saigo, M. Fractional integrals and derivatives of Mittag-Leffler type function (Russian). Dokl. Akad. Nauk Belarusi 1995, 39, 22–26. [Google Scholar]
- Kilbas, A.A.; Saigo, M. H-Transforms: Theory and Applications; Ser. Analytic Methods and Special Functions; CRC Press: London, UK; New York, NY, USA, 2004; Volume 9. [Google Scholar]
- Kilbas, A.A.; Saigo, M.; Saxena, R.K. Generalized Mittag-Leffler function and generalized fractional calculus operators. Integr. Transf. Spec. Funct. 2004, 15, 31–49. [Google Scholar] [CrossRef]
- Saxena, R.K. Certain properties of generalized Mittag-Leffler function. In Proceedings of the Third Annual Conference of the Society for Special Functions and Their Applications, Varanasi, India, 4–6 March 2002; Volume 3, pp. 75–81.
- Saxena, R.K.; Saigo, M. Certain properties of fractional calculus operators associated with generalized Mittag-Leffler function. Fract. Calc. Appl. Anal. 2005, 8, 141–154. [Google Scholar]
- Özarslan, M.A.; Yilmaz, B. The extended Mittag-Leffler function and its properties. J. Inequal. Appl. 2014, 85, 1–10. [Google Scholar] [CrossRef]
- Sneddon, I.N. The use of the Integral Transforms; Tata McGraw-Hill: New Delhi, India, 1979. [Google Scholar]
- Wright, E.M. The asymptotic expansion of the generalized hypergeometric functions. J. Lond. Math. Soc. 1935, 19, 286–293. [Google Scholar]
- Wright, E.M. The asymptotic expansion of the generalized hypergeometric functions. Proc. Lond. Math. Soc. 1940, 46, 389–408. [Google Scholar] [CrossRef]
- Fox, C. The G and H-functions as symmetrical Fourier kernels. Trans. Amer. Math. Soc. 1961, 98, 395–429. [Google Scholar]
- Mathai, A.M.; Saxena, R.K. The H-Functions with Applications in Statistics and Other Disciplines; John Wiley and Sons: New York, NY, USA; London, UK; Sydney, Australia, 1978. [Google Scholar]
- Mathai, A.M.; Saxena, R.K.; Haubold, H.J. The H-Functions: Theory and Applications; Springer: New York, NY, USA, 2010. [Google Scholar]
- Kilbas, A.A.; Srivastava, H.M.; Trujillo, J.J. Theory and Applications of Fractional Differential Equations; North-Holland Mathematical Studies; Elsevier (North-Holland) Science Publishers: Amsterdam, The Netherland; London, UK; New York, NY, USA, 2006; Volume 204. [Google Scholar]
- Samko, S.G.; Kilbas, A.A.; Marichev, O.I. Fractional Integrals and Derivatives: Theory and Applications; Gordon and Breach: Yverdon, Switzerland, 1993. [Google Scholar]
- Hilfer, R. (Ed.) Applications of Fractional Calculus in Physics; World Scientific Publishing Company: Singapore, Singapore; Hackensack, NJ, USA; London, UK; Hong Kong, China, 2000.
- Srivastava, H.M.; Tomovski, Ẑ. Fractional calculus with an integral operator containing a generalized Mittag-Leffler function in the kernal. Appl. Math. Comput. 2009, 211, 198–210. [Google Scholar] [CrossRef]
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