EUROPEAN JOURNAL OF PURE AND APPLIED MATHEMATICS Vol. 15, No. 3, 2022, 916-923 ISSN 1307-5543 – ejpam.com Published by New York Business Global Triple Integral involving the Bessel-Integral Function Jiv(z): Derivation and Evaluation Robert Reynolds1,∗, Allan Stauffer1 1 Department of Mathematics and Statistics, Faculty of Science, York University, Toronto, Ontario, Canada, M3J1P3 Abstract. A triple integral involving the Bessel-integral function Jiv(z) is derived and evaluated for certain real numbers of the parameters. The derived integral allows a representation in terms of the product of the Hurwitz-Lerch zeta and Gamma functions with seven parameters. All the results in this work are new. 2020 Mathematics Subject Classifications: 30E20, 33-01, 33-03, 33-04, 33-33B Key Words and Phrases: Triple integral, Bessel-integral function, Hurwitz-Lerch zeta function, Catalan’s constant 1. Significance Statement The Bessel integral function Jiv(z) has been studied in many works namely; the oper- ational solution of linear differential equations and properties of their solutions [11], and the expansion of the works of by van der Pol were published in [7] and [5]. In the book of Prudnikov et al. [9] section (3.3.2) some very interesting triple integrals containing the Bessel function of order zero J0(z) are tabled without derivation. In this current work we aim to expand on the Table of Prudnikov et al. by deriving and evaluating a triple integral involving the Bessel integral function given in Table (3.37.4) in [1] and provide a formal derivation by expressing the triple integral in terms of the Hurwitz-Lerch zeta and Gamma functions. 2. Introduction In this paper we derive the triple definite integral given by∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 v2Γ(v) xm−1y−m+v+1z−m−v+1(αx)ve−by2−cz2 logk−1 ∗Corresponding author. DOI: https://doi.org/10.29020/nybg.ejpam.v15i3.4259 Email addresses: milver@my.yorku.ca (R. Reynolds), stauffer@yorku.ca (A. Stauffer) https://www.ejpam.com 916 © 2022 EJPAM All rights reserved. R. Reynolds, A. Stauffer / Eur. J. Pure Appl. Math, 15 (3) (2022), 916-923 917( ax yz )( m log ( ax yz ) + k ) 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4 x2α2 ) dxdydz (1) where the parameters k, a, b, c, v,m are general complex numbers and α ∈ R+, Re(b), Re(c) > 0, Re(m) < 0 < Re(v) < 2. This definite integral will be used to derive special cases in terms of special functions and fundamental constants. The derivations follow the method used by us in [10]. This method involves using a form of the generalized Cauchy’s integral formula given by yk Γ(k + 1) = 1 2πi ∫ C ewy wk+1 dw. (2) where C is in general an open contour in the complex plane where the bilinear concomitant has the same value at the end points of the contour. We then multiply both sides by a function of x, y and z, then take a definite triple integral of both sides. This yields a definite integral in terms of a contour integral. Then we multiply both sides of Equation (2) by another function of x y and z and take the infinite sums of both sides such that the contour integral of both equations are the same. 3. Definite Integral of the Contour Integral We use the method in [10]. The variable of integration in the contour integral is s = w+m. The cut and contour are in the first quadrant of the complex s-plane. The cut approaches the origin from the interior of the first quadrant and the contour goes round the origin with zero radius and is on opposite sides of the cut. Using a generalization of Cauchy’s integral formula we form the triple integral by replacing y by log ( ax yz ) and multiplying by (3)− m2−vxm−1y−m+v+1z−m−v+1(αx)ve−by2−cz2 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4x 2α2 ) v2Γ(v) for the first equation and replacing y by log ( ax yz ) and replacing k → k−1 and multiplying by (4) 2−vxm−1y−m+v+1z−m−v+1(αx)ve−by2−cz2 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4x 2α2 ) v2Γ(v) to form the second equation. Next we add both equations then take the definite triple integral with respect to x ∈ [0,∞), y ∈ [0,∞) and z ∈ [0,∞) to obtain∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 v2Γ(v)Γ(k + 1) xm−1y−m+v+1z−m−v+1(αx)ve−by2−cz2 logk−1 ( ax yz )( m log ( ax yz ) + k ) 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4 x2α2 ) dxdydz R. Reynolds, A. Stauffer / Eur. J. Pure Appl. Math, 15 (3) (2022), 916-923 918 = − 1 2πi ∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 ∫ C 1 v2Γ(v) 2−vaww−k−1(m+ w)xm+w−1(αx)ve−by2−cz2 y−m+v−w+1z−m−v−w+1 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4 x2α2 ) dwdxdydz = − 1 2πi ∫ C ∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 v2Γ(v) 2−vaww−k−1(m+ w)xm+w−1(αx)ve−by2−cz2 y−m+v−w+1z−m−v−w+1 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4 x2α2 ) dxdydzdw = 1 2πi ∫ C πaww−k−12m+w−3α−m−wb 1 2 (m−v+w−2)c 1 2 (m+v+w−2) csc ( 1 2 π(m+ v + w) ) dw (5) from equation (4) in [2], equation (3.37.4.1) in [1] and equation (3.326.2) in [4] where 0 < Re(w + m) < 2, Re(m) < Re(v) < 2, α ∈ R+ and using the reflection formula (8.334.3) in [4] for the Gamma function. We are able to switch the order of integration over x, y and z using Fubini’s theorem since the integrand is of bounded measure over the space C× [0,∞)× [0,∞)× [0,∞) 4. The Hurwitz-Lerch zeta Function and Infinite Sum of the Contour Integral In this section we use Equation (2) to derive the contour integral representations for the Hurwitz-Lerch zeta function. 4.1. The Hurwitz-Lerch zeta Function The Hurwitz-Lerch zeta function (25.14) in [3] has a series representation given by Φ(z, s, v) = ∞∑ n=0 (v + n)−szn (6) where |z|< 1, v ̸= 0,−1, .. and is continued analytically by its integral representation given by Φ(z, s, v) = 1 Γ(s) ∫ ∞ 0 ts−1e−vt 1− ze−t dt = 1 Γ(s) ∫ ∞ 0 ts−1e−(v−1)t et − z dt (7) where Re(v) > 0, and either |z|≤ 1, z ̸= 1, Re(s) > 0, or z = 1, Re(s) > 1. R. Reynolds, A. Stauffer / Eur. J. Pure Appl. Math, 15 (3) (2022), 916-923 919 4.2. Infinite sum of the Contour Integral Using equation (2) and replacing y by log(a)−log(α)+ log(b) 2 + log(c) 2 + 1 2 iπ(2y+1)+log(2) then multiplying both sides by −iπ2m−2α−mb 1 2 (m−v−2)c 1 2 (m+v−2)e 1 2 iπ(2y+1)(m+v) taking the infinite sum over y ∈ [0,∞) and simplifying in terms of the Hurwitz-Lerch zeta function we obtain (8) − 1 Γ(k + 1) iπk+12m−2α−mb 1 2 (m−v−2)c 1 2 (m+v−2)e 1 2 iπ(k+m+v) Φ ( eiπ(m+v),−k, −2i log(2a)− i log(b)− i log(c) + 2i log(α) + π 2π ) = − 1 2πi ∞∑ y=0 ∫ C iπ2m−2aww−k−1α−mb 1 2 (m−v−2)c 1 2 (m+v−2) exp ( 1 2 (w(−2 log(α) + log(b) + log(c) + log(4)) + iπ(2y + 1)(m+ v + w)) ) dw = − 1 2πi ∫ C ∞∑ y=0 iπ2m−2aww−k−1α−mb 1 2 (m−v−2)c 1 2 (m+v−2) exp ( 1 2 (w(−2 log(α) + log(b) + log(c) + log(4)) + iπ(2y + 1)(m+ v + w)) ) dw = 1 2πi ∫ C πaww−k−12m+w−3α−m−wb 1 2 (m−v+w−2)c 1 2 (m+v+w−2) csc ( 1 2 π(m+ v + w) ) dw from equation (1.232.3) in [4] where Im ( 1 2π(m+ v + w) ) > 0 in order for the sum to converge. 5. Definite Integral in terms of the Hurwitz-Lerch zeta Function Theorem 1. For all k, a ∈ C, Re(b) > 0, Re(c) > 0, Re(m) < 0 < Re(v) < 2, α ∈ R+,∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 v2Γ(v) xm−1y−m+v+1z−m−v+1(αx)ve−by2−cz2 logk−1 ( ax yz )( m log ( ax yz ) + k ) 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4 x2α2 ) dxdydz = iπk+1α−m2m+v−2b 1 2 (m−v−2)c 1 2 (m+v−2)e 1 2 iπ(k+m+v) Φ ( eiπ(m+v),−k, −2i log(2a)− i log(b)− i log(c) + 2i log(α) + π 2π ) (9) R. Reynolds, A. Stauffer / Eur. J. Pure Appl. Math, 15 (3) (2022), 916-923 920 Proof. The right-hand sides of relations (5) and (8) are identical; hence, the left-hand sides of the same are identical too. Simplifying with the Gamma function yields the desired conclusion. Example 1. The degenerate case.∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 v2Γ(v) mxm−1y−m+v+1z−m−v+1(αx)ve−by2−cz2 1F2 ( v 2 ; v 2 + 1, v + 1;−1 4 x2α2 ) dxdydz = πα−m ( −2m+v−3 ) b 1 2 (m−v−2)c 1 2 (m+v−2) csc ( 1 2 π(m+ v) ) (10) Proof. Use equation (9) and set k = 0 and simplify using entry (2) in Table below (64:12:7) in [8]. Example 2. The Hurwitz zeta function ζ(s, v)∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 25x5/3Γ ( 5 3 )9y10/3(αx)5/3e−by2−cz2 ( k − 2 3 log ( ax yz )) logk−1 ( ax yz ) 1F2 ( 5 6 ; 11 6 , 8 3 ;−1 4 x2α2 ) dxdydz = iα2/32k−1e 1 2 iπ(k+1)πk+1ζ ( −k, −2i log(2a)−i log(b)−i log(c)+2i log(α)+π 4π ) b13/6 √ c − iα2/32k−1e 1 2 iπ(k+1)πk+1ζ ( −k, 12 ( −2i log(2a)−i log(b)−i log(c)+2i log(α)+π 2π + 1 )) b13/6 √ c (11) Proof. Use equation (9) and set m = −2/3, v = 5/3 and simplify using entry (4) in Table below (64:12:7) in [8]. Example 3. (12 ) ∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 y10/3e−y2−z2 ( 2 log ( − x yz ) + 3 ) 1F2 ( 5 6 ; 11 6 , 8 3 ;−x2 ) log2 ( − x yz ) dxdydz = 25 24 i(π − 4)Γ ( 5 3 ) Proof. Use equation (11) and set a = −1, b = c = α = 1 and simplify. R. Reynolds, A. Stauffer / Eur. J. Pure Appl. Math, 15 (3) (2022), 916-923 921 Example 4. The zeta function of Riemann ζ(s).∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 y10/3e−y2−z2 ( 3k − 2 log ( ix 2yz )) logk−1 ( ix 2yz ) 1F2 ( 5 6 ; 11 6 , 8 3 ;−x2 4 ) dxdydz = 25 6 ( 2k+1 − 1 ) e iπk 2 πk+1Γ ( 5 3 ) ζ(−k) (13) Proof. Use equation (11) and set a = i/2, b = c = α = 1 and simplify using entry (2) in Table below (64:7) in [8]. Example 5.∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 log2 ( x yz )xv−1e−y2−z2y−m−p+v+1z−m−p−v+1 ( ymzmxp ( p log ( x yz ) − 1 ) + xmypzp ( 1−m log ( x yz ))) 1F2 (v 2 ; v 2 + 1, v + 1;−x2 ) dxdydz = 1 2 vΓ(v + 1) ( tanh−1 ( e 1 2 iπ(p+v) ) − tanh−1 ( e 1 2 iπ(m+v) )) (14) Proof. Use equation (9) and form a second equation by replacing m → p and take their difference. Next set k = −1, a = b = c = 1, α = 2 and simplify using entry (3) in Table below (64:12:7) in [8]. Example 6.∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 3 √ x log2 ( x yz )y44/15z4/15e−y2−z2 (( 10 15 √ y 15 √ z − 9 15 √ x ) log ( x yz ) − 15 ( 15 √ x− 15 √ y 15 √ z )) 1F2 ( 2 3 ; 5 3 , 7 3 ;−x2 ) dxdydz = −5Γ ( 7 3 ) tanh−1 ( 2 + 3 sin ( 2π 15 ) − 2 ) (15) Proof. Use equation (14) and set m = −2/3, p = −3/5, v = 4/3 and simplify. R. Reynolds, A. Stauffer / Eur. J. Pure Appl. Math, 15 (3) (2022), 916-923 922 Example 7. The Polylogarithm function Lin(z).∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 e−y2−z2xm+v−1y−m+v+1z−m−v+1 logk−1 ( ix 2yz ) ( k +m log ( ix 2yz )) 1F2 ( v 2 ; v 2 + 1, v + 1;−x2 4 ) dxdydz = iπk+1v2m+v−2Γ(v + 1)e− 1 2 iπ(−k+m+v)Li−k ( eiπ(m+v) ) (16) Proof. Use equation (9) and set a = i/2, b = c = α = 1 and simplify using equation (64:12:2) in [8]. Example 8. Catalan’s constant C.∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 √ x log3 ( ix 2yz )√zy2v+ 1 2 e−y2−z2 ( −2 + ( 1 2 − v ) log ( ix 2yz )) 1F2 ( v 2 ; v 2 + 1, v + 1;−x2 4 ) dxdydz = ie 3iπ 4 ( −π2 48 + iC ) vΓ(v + 1) 2 √ 2π (17) Proof. Use equation (16) and set k = −2,m = 1/2 − v and simplify using equation (2.2.1.2.7) in [6]. Example 9. The Hypergeometric function s−1 2F1 (1, s, 1 + s; z).∫ ∞ 0 ∫ ∞ 0 ∫ ∞ 0 1 √ x log2 ( − x 2yz )√zy2v+ 1 2 e−y2−z2 (( 1 2 − v ) log ( − x 2yz ) − 1 ) 1F2 ( v 2 ; v 2 + 1, v + 1;−x2 4 ) dxdydz = ( 1 2 − i 2 )( −1 + 2F1 ( 1 2 , 1; 3 2 ; i )) vΓ(v + 1) (18) Proof. Use equation (9) and set k = −1, a = −1/2, b = c = α = 1,m = 1/2 − v and simplify using equation (9.559) in [4]. REFERENCES 923 6. Discussion In this paper, we have presented a novel method for deriving a new integral transform involving the Bessel integral function Jiv(z) along with some interesting definite integrals using contour integration. The results presented were numerically verified for both real and imaginary and complex values of the parameters in the integrals using Mathematica by Wolfram. References [1] Yu. A. Brychkov, O. I. Marichev, and N. V. Savischenko. Handbook of Mellin tran- forms. CRC Press., 2019. 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