1. Introduction
The generalized hypergeometric function is defined [
1,
2,
3,
4] by
where
and
are complex parameters such that the denominators of the summands on the right-hand side are not equal to zero or negative integers.
The symbol
is the well-known Pochhammer symbol [
5] for any complex number
given by
In terms of gamma function, it can be written as
The series given by (
1) is convergent for all
by the ratio test [
1]. For
, it converges everywhere and converges nowhere for
. Further, if
, it converges absolutely for
provided
holds and is conditionally convergent for
and
if
and diverges for
and
if
.
It is interesting to mention here that the generalized hypergeometric function exhibits symmetry in both its numerator and denominator parameters. Any reordering of the numerator parameters
does not alter the function, and, similarly, any reordering of the denominator parameters
also yields the same function [
6].
The result will be significant whenever a generalized hypergeometric series can be summed in terms of gamma functions because there are very few of these summation theorems in the literature. However, in this paper, we shall mention the following Watson summation theorem viz,
provided
.
For the two integer parameters
m and
n, let us denote
Clearly, for
, we obtain (
3).
In 1992, Lavoie, Grondin, and Rathie [
3] obtained the generalization of Watson series (
3) with two integer parameters
m and
n in the following form:
for
. Here, as usual,
is the greatest integer less than or equal to x and its modulus is denoted by
. For the values of the coefficients
,
, and
one can refer to [
3]. Later, in 2012, Chu [
7] established analytical formulas explicitly for Watson series (
3) with two integer parameters m ∈
and n∈
where
in the following form:
On the other hand, the Eulerian integrals are an important class of finite integrals. The integrals of this type can be written in the form
provided
and
Next, if the function
f(
x) in the integrand is such that it can be expanded in a power series such as
provided that the radius of convergence of (10) is not greater than unity, then, from (9), we have
Evaluating the beta integral, and after a little simplification, we have
This is a general result.
Further,
f(
x) is in the form of a Gauss hypergeometric function
2F1 as follows:
Hence,
Many summations theorems may be employed to sum the
3F2 function that appeared on the right-hand side of (14). For example, if, in (14), we take
,
, and
, then (14) takes the following form:
We now observe that the
3F2 appearing on the right-hand side of (15) can be evaluated with the help of the classical Watson summation theorem (3), and, finally, we obtain the following Eulerian integral:
provided
,
, and
is the same as given in (3).
Similar results can easily be obtained by employing the following Edwards double integral [
8]:
provided
and
and the following well-known gamma integral
provided
and
The details are given in the following sections.
The rest of the paper is organized as follows.
In
Section 2, eight Eulerian-type single integrals involving a hypergeometric function have been evaluated in terms of a gamma function by using results (5) to (8).
Section 3 deals with sixteen Eulerian-type double integrals involving a hypergeometric function and eight Laplace-type integrals using a generalized hypergeometric function are obtained in
Section 4. We discuss several interesting special cases of our main results in each section.
We conclude this section by remarking that the integrals (single and multiple) involving hypergeometric functions play an important role in the area of applied mathematics, statistics, engineering, physics, and several other branches. A large number of interesting applications can be seen in the seventh chapter of the standard text of Exton [
9].
2. Evaluation of Eulerian-Type Integrals Involving Hypergeometric Function
The eight new classes of Eulerian-type integrals involving generalized hypergeometric functions to be established in this section are asserted in the following theorems.
Theorem 1. For , , and , the following result holds true:where is the same as in (5). Proof. To prove the result (
18), denoting the left-hand side of (
18) by
I, expressing
2F1 as a series, changing the order of integration and summation, which is easily seen to be justified due to the uniform convergence of the series in the interval
, and evaluating the beta integral, we have
Using (2) and after some simplification, we have
Summing up the series, we finally obtain
Now, we observe that the
3F2’s appearance can be evaluated with the help of the result (
5) and we easily arrive at the right side of (
18). This completes the proof of the result (
18) asserted in Theorem 1. □
Corollary 1. In Theorem 1, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: In the same manner, the results and the special cases given in the following theorems and corollaries can be easily established by applying the corresponding summation Formulas (
5) to (
8). Hence, they are given here without proof.
Theorem 2. For , , , and , the following result holds true:where is the same as in (5). Corollary 2. In Theorem 2, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: Theorem 3. For , , and , the following result holds true:where is the same as in (
6).
Corollary 3. In Theorem 3, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: Theorem 4. For , , , and , the following result holds true:where is the same as in (
6).
Corollary 4. In Theorem 4, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: Theorem 5. For , , and , the following result holds true:where is the same as in (
7).
Corollar 5. In Theorem 5, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: Theorem 6. For , , , and , the following result holds true:where is the same as in (
7).
Corollary 6. In Theorem 6, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: Theorem 7. For , , and , the following result holds true:where is the same as in (
8).
Corollary 7. In Theorem 7, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: Theorem 8. For , , , and , the following result holds true:where is the same as in (
8).
Corollary 8. In Theorem 8, if we take m = 0, n = 1; m = 1, n = 0; and m = n = 1, we respectively obtain the following integrals: Remark 1. It is interesting to mention here that in Theorem 1, 3, 5, or 7 and in Theorem 2, 4, 6, or 8, if we set , then we respectively obtain the following interesting integrals: 4. Evaluation of Laplace-Type Integrals Involving Hypergeometric Function
The eight new classes of Laplace- type integrals involving a hypergeometric function to be established in this section are asserted in the following theorems.
Theorem 25. For , , and , the following result holds true:where is the same as given in (
5).
Proof. To derive the result given in the Theorem 25, we express
as a series, change the order of integration and summation, and then evaluate the integral. We finally arrive at the right-hand side of (
42). □
Corollary 25. In Theorem 25, if we take ; ; and , we obtain the following integrals: In exactly the same manner, the integrals given in the following Theorems 26, 27, 28, 29, 30, 31, and 32 can be evaluated; thus, they are given here without proof.
Theorem 26. For , , and , the following result holds true:where is the same as given in (
5).
Corollary 26. In Theorem 26, if we take ; ; and , we obtain the following integrals: Theorem 27. For , , and the following result holds true:where is the same as given in (
6).
Corollary 27. In Theorem 27, if we take ; ; and , we obtain the following integrals: Theorem 28. For , , and , the following result holds true:where is the same as given in (
6).
Corollary 28. In Theorem 28, if we take ; ; and , we obtain the following integrals: Theorem 29. For , , and the following result holds true:where is the same as given in (
7).
Corollary 29. In Theorem 29, if we take ; ; and , we obtain the following integrals: Theorem 30. For , , and , the following result holds true:where is the same as given in (
7).
Corollary 30. In Theorem 30, if we take ; ; and , we obtain the following integrals: Theorem 31. For , , and the following result holds true:where is the same as given in (
8).
Corollary 31. In Theorem 31, if we take ; ; and , we obtain the following integrals: Theorem 32. For , , and , the following result holds true:where is the same as given in (
8).
Corollary 32. In Theorem 32, if we take ; ; and , we obtain the following integrals: Remark 3. It is interesting to mention here that in Theorem 25, 27, 29, or 31 and in Theorem 26, 28, 30, or 32, if we set we respectively obtain the following interesting integrals:where is given in (
3).
where is given in (
3).
5. Conclusions
In this paper, we have evaluated a new class of Eulerian-type integrals (single and double) and Laplace -type integrals involving a hypergeometric function by employing four generalizations of the classical Watson summation theorem with two integer parameters discovered by Chu. Several interesting special cases have also been given. Hypergeometric integrals are widely recognized for their significant role in various fields, including statistics, mathematical physics, and quantum chemistry. In statistics, they provide the foundation for representing probability distributions such as the beta and gamma distributions, along with density and cumulative distribution functions. In the realm of physics, these integrals appear in the study of elastic plate vibrations, heat conduction within cylinders, viscous fluid motion, and certain electrical networks. They also contribute to the analysis of heat flow in solids within conducting media and the exploration of specific non-linear oscillation phenomena. Quantum chemistry employs hypergeometric integrals in molecular calculations, while communications engineering utilizes them in contexts like Gaussian noise analysis. Additional applications include their use in electrical impedance theory and combinatorial analysis. Since all the results obtained in this paper are given in terms of the gamma function, they may be potentially useful in applied mathematics, engineering mathematics, and mathematical physics.
We conclude the paper by remarking that, following the same lines, Eulerian-type integrals (single and double) and Laplace -type integrals by employing generalizations of Dixon’s and Whipple’s summation theorems are under investigation and we will form two subsequent papers in this direction.