Hindawi Publishing Corporation Discrete Dynamics in Nature and Society Volume 2012, Article ID 974632, 13 pages doi:10.1155/2012/974632 Research Article Hermite Polynomials and their Applications Associated with Bernoulli and Euler Numbers Dae San Kim,1 Taekyun Kim,2 Seog-Hoon Rim,3 and Sang Hun Lee4 1 Department of Mathematics, Sogang University, Seoul 121-742, Republic of Korea Department of Mathematics, Kwangwoon University, Seoul 139-701, Republic of Korea 3 Department of Mathematics Education, Kyungpook National University, Taegu 702-701, Republic of Korea 4 Division of General Education, Kwangwoon University, Seoul 139-701, Republic of Korea 2 Correspondence should be addressed to Taekyun Kim, taekyun64@hotmail.com Received 7 May 2012; Accepted 15 May 2012 Academic Editor: Garyfalos Papaschinopoulos Copyright q 2012 Dae San Kim et al. 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. We derive some interesting identities and arithmetic properties of Bernoulli and Euler polynomials from the orthogonality of Hermite polynomials. Let Pn {px ∈ Qx | deg px ≤ n} be the n 1-dimensional vector space over Q. Then we show that {H0 x, H1 x, . . . , Hn x} is a good basis for the space Pn for our purpose of arithmetical and combinatorial applications. 1. Introduction As is well known, the Euler polynomials, En x, are defined by the generating function as follows: et ∞ tn 2 ext eExt En x n! 1 n0 1.1 see 1–8, with the usual convention about replacing En x by En x. In the special case, x 0, En 0 En is called the nth Euler number. From 1.1 and definition of Euler numbers, we note that n En x E x n n l0 l El x n−l with the usual convention about replacing En by En . n n En−l xl l l0 1.2 2 Discrete Dynamics in Nature and Society The Bernoulli numbers are defined as B 1n − Bn δ1,n B0 1, 1.3 see 9–14, where δk,n is a Kronecker symbol. As is well known, Bernoulli polynomials are also defined by n Bn x B x n n l l0 Bl x n−l n n Bn−l xl l l0 1.4 with the usual convention about replacing Bn by Bn see 1, 15–18. The Hermite polynomials are defined by the generating function as follows: 2 e2xt−t eHxt ∞ tn Hn x n! n0 1.5 see 5, 19, with the usual convention about replacing H n x by Hn x. From 1.5, we can derive the following identities: Hn x ∂ ∂t n e n x2 2xt−t2 −1 e ∂ ∂x e x2 t0 n 2 e−x−t ∂ ∂t n e −x−t2 t0 n x2 −1 e t0 dn −x2 e . dxn 1.6 Let us consider two operators as follows: df 2 d 2 e−x f 2xf − , f −→ O1 f − ex dx dx df d 2 2 f −→ O2 f ex /2 x − . e−x /2 f 2xf − dx dx 1.7 By 1.7, we get O1 O2 . In particular, if we take f 1, then we have −e x2 d −x2 e dx e x2 /2 d 2 x− e−x /2 . dx 1.8 We note that n x2 −1 e dn −x2 e dxn d −x2 e −e dx x2 n . 1.9 Discrete Dynamics in Nature and Society 3 From 1.8, we note that n x2 −1 e dn e−x dxn 2 de−x −e dx 2 n x2 n d 2 2 e−x /2 ex /2 x − dx d n −x2 /2 2 ex /2 x − e . dx 1.10 Thus, by 1.10, we get Hn x e x2 /2 d x− dx n e−x 2 1.11 /2 see 5, 19–23. In the special case, x 0, Hn 0 Hn are called the Hermite numbers. From 1.5, we can derive the following identities: Hn x H 2xn n n l0 l Hn−l 2l xl 1.12 cf. 5, 19, with the usual convention about replacing H n by Hn . It is easy to show that ∞ ∞ tn −1n 2n 2 t . Hn e−t n! n! n0 l0 1.13 By comparing coefficients on the both sides of 1.13, we get H2n −1n 2n2n − 1 · · · n 1 −1n 2n! , n! H2n−1 0, 1.14 where n ∈ N. From 1.12, we have dHn x 2nHn−1 x n ∈ N. dx 1.15 Let Pn {p ∈ Qx | deg px ≤ n} be the n 1-dimensional vector space over Q. Probably, {1, x, x2 , . . . , xn } is the most natural basis for this space. But {H0 x, H1 x, H2 x, . . . , Hn x} is also a good basis for the space Pn , for our purpose of arithmetical and combinatorial applications. For px ∈ Pn , px n Ck Hk x, 1.16 k0 for some uniquely determined bl ∈ Q. The purpose of this paper is to develop methods for computing Ck from the information of px. By using these methods, we define some interesting identities. 4 Discrete Dynamics in Nature and Society 2. Properties of Hermite Polynomials From 1.5 and 1.13, we note that ∞ Hm tm 1 m0 ∞ m! ∞ 2l t l0 t2m H2m 2m! m0 l! ∞ 2l2l − 1 · · · l 1 l0 2l! t 2l ∞ n t2n 2l2l − 1 · · · l 1 H2n−2l 2n! 2l!2n − 2l! 2n! n0 l0 2.1 ∞ n t2n 2l 2n . l! H2n−2l l 2l 2n! n0 l0 Thus, by 2.1, we obtain the following recurrence formula. Proposition 2.1. For n ∈ Z N ∪ {0}, one has n 1, if n 0 2l 2n l! H2n−2l . l 2l 0, if n / 0 l0 2.2 ∞ ∞ 2 tn tn 2 Hn −x e2t−x−t e2x−t−−t Hn x−1n . n! n! n0 n0 2.3 By, 1.5, we get From 2.3, we can derive the following reflection symmetric identity of Hn x: Hn −x −1n Hn x. 2.4 ∂ 2xt−t2 2 e 2x − 2te2xt−t . ∂t 2.5 By 1.5, we easily see that Discrete Dynamics in Nature and Society 5 Thus, by 1.5 and 2.5, we get ∂ ∂t ∞ tn Hn x n! n0 LHS of 2.5 RHS of 2.5 ∞ tn Hn x 2x − 2t . n! n0 ∞ ∞ tn−1 tn Hn x Hn1 x , n! n − 1! n0 n1 ∞ n0 tn 2xHn x n! − ∞ 2Hn x n0 ∞ 2xHn x n0 2.7 tn1 n! ∞ ∞ tn tn 2xHn x − 2Hn−1 x n! n − 1! n0 n1 2.6 2.8 ∞ tn tn − 2nHn−1 x . n! n1 n! Thus, by 2.6 and 2.7, we get Hn1 x 2xHn x − 2nHn−1 x, n ∈ N. 2.9 From 1.15 and 2.9, we note that Hn1 x − 2xHn x Hn x 0. 2.10 Differentiating on both sides, we have 2n 1Hn x − 2Hn x − 2xHn x Hn x 0. 2.11 Hn x − 2xHn x 2nHn x 0. 2.12 Thus, we have From 2.12, we note that Hn x is a solution of the following second-order linear differential equation: u − 2xu 2nu 0. 2.13 From 1.5, we note that ∞ tn 2 Hn x e2tx−t n! m0 ∞ n0 ∞ ∞ 2xl l −1k 2k t t l! k! l0 k0 n/2 −1k n!2xn−2k tn k0 k!n − 2k! n! . 2.14 6 Discrete Dynamics in Nature and Society Thus, by 2.14, we get Hn x n/2 k0 −1k n! 2xn−2k k!n − 2k! ⎧ n/2 −1n/2−l n!22l 2l ⎪ ⎪ ⎪ x , ⎪ ⎪ ⎨ l0 n/2 − l!2l! ⎪ ⎪ n−1/2 ⎪ ⎪ ⎪ ⎩ l0 if n ≡ 0 mod 2, 2.15 −1n−1/2−l n!22l1 x2l1 , if n ≡ 1 mod 2. n − 1/2 − l!2l 1! 3. Main Results By 1.6, we easily get ∞ −∞ e−x Hn xHm xdx −1n 2 ∞ −∞ dn −x2 e Hm xdx. dxn 3.1 From 3.1, we note that ∞ −∞ √ 2 e−x Hn xHm xdx 2n n! πδm,n . 3.2 It is easy to show that ∞ −∞ e −x2 l x dx ⎧ 0 ⎪ ⎪ ⎨ if l ≡ 1 mod 2, √ l! π ⎪ ⎪ if l ≡ 0 mod 2, ⎩ l 2 l/2! 3.3 where l ∈ Z N ∪ {0}. By 3.3, we get ∞ −∞ n −x2 d e dxn x dx m ⎧ 0 ⎪ ⎪ ⎨ ⎪ ⎪ ⎩ if n > m or n ≤ m with n − m ≡ 1 mod 2, n√ m!−1 π if n ≤ m with n − m ≡ 0 mod 2. 2m−n m − n/2! 3.4 From 3.2, we note that H0 x, H1 x, . . . , Hn x are orthogonal basis for the space Pn {px ∈ Qx | deg px ≤ n} with respect to the inner product px, qx ∞ −∞ e−x pxqxdx. 2 3.5 Discrete Dynamics in Nature and Society 7 For px ∈ Pn , the polynomial px is given by px ∞ Ck Hk x, 3.6 k0 where 1 √ px, Hk x π ∞ k −x2 d e −1k k √ pxdx. 2 k! π −∞ dxk Ck 2k k! 3.7 Let us take px xn ∈ Pn . For n ≡ 0 mod 2, we compute Ck in 3.6 as follows −1k Ck k √ 2 k! π ∞ −∞ dk e−x dxk 2 xn dx ⎧ √ ⎪ −1k n! π −1k ⎪ ⎨ × if k ≡ 0 mod 2, √ 2k k! π 2n−k n − k/2! ⎪ ⎪ ⎩ 0 if k ≡ 1 mod 2. 3.8 Let n ≡ 1 mod 2. Then we have ∞ k −x2 d e −1k xn dx Ck k √ 2 k! π −∞ dxk ⎧ n! ⎪ ⎨ if k ≡ 1 mod 2, n 2 k!n − k/2! ⎪ ⎩0 if k ≡ 0 mod 2. 3.9 Therefore, by 3.6, 3.8, and 3.9, we obtain the following proposition. Proposition 3.1. One has x2n x2n1 n 1 2n! H2k x, 22n k0 2k!n − k! n 1 2n 1! H2k1 x. 22n1 k0 2k 1!n − k! 3.10 Let us take px Bn x. From 3.4, P x can be rewritten by Bn x n k0 Ck Hk x, 3.11 8 Discrete Dynamics in Nature and Society where −1k Ck k √ 2 k! π ∞ −∞ dk e−x dxk 2 3.12 Bn xdx. By integrating by parts, we get ∞ −∞ dk e−x dxk 2 Bn x −n−n − 1 · · · −n − k 1 −1k ∞ −∞ e−x Bn−k xdx 2 ∞ n−k n! 2 n−k e−x xl dx Bn−k−l l n − k! l0 −∞ −1k n! n − k! √ l! π n − k!Bn−k−l × l l!n − k − l! 2 l/2! 0≤l≤n−k l≡0 mod 2 √ −1k n! π 0≤l≤n−k l≡0 mod 2 3.13 Bn−k−l . n − k − l!2l l/2! Thus, from 3.11 and 3.13, we have Ck n! 2k k! 0≤l≤n−k l≡0 mod 2 Bn−k−l . n − k − l!2l l/2! 3.14 Therefore, by 3.11 and 3.14, we obtain the following theorem. Theorem 3.2. For n ∈ Z , one has Bn x n! n k0 0≤l≤n−k l≡0 mod 2 Bn−k−l Hk x. 2kl k!n − k − l!l/2! 3.15 Remark 3.3. Let us take px En x. Then, by the same method, we obtain the following identity: En x n! n k0 0≤l≤n−k l≡0 mod 2 2kl k!n En−k−l Hk x. − k − l!l/2! 3.16 Now, we consider px Hn x. From 3.6, we note that px can be rewritten as Hn x n Ck Hk x, k0 3.17 Discrete Dynamics in Nature and Society 9 where −1k Ck k √ 2 k! π ∞ −∞ dk e−x dxk 2 3.18 Hn xdx. By integrating by parts, we get ∞ −∞ dk e−x dxk 2 Hn xdx −2n · · · −2n − k 1 ∞ −∞ e−x Hn−k xdx 2 ∞ n−k −1k 2k n! 2 n−k l e−x xl dx 2 Hn−k−l l n − k! l0 −∞ −1k 2k n! n − k! n−k l0 l≡0 mod 2 √ 2l n − k! l! π Hn−k−l l l!n − k − l! 2 l/2! n−k √ −1k 2k n! π l0 l≡0 mod 2 3.19 Hn−k−l . n − k − l!l/2! From 3.17 and 3.19, we note that Ck n! k! k −1 √ π 2k k! 0≤l≤n−k l≡0 mod 2 ⎛ ⎞ ⎜ k k √ ×⎜ ⎝−1 2 n! π 0≤l≤n−k l≡0 mod 2 ⎟ Hn−k−l ⎟ n − k − l!l/2! ⎠ 3.20 Hn−k−l . n − k − l!l/2! Therefore, by 3.17 and 3.20, we obtain the following theorem. Theorem 3.4. For n ∈ Z , one has Hn x n! n Hn−k−l Hk x. k!n − k − l!l/2! 3.21 Hn−k−l n!Hn x Hk x . k!n − k − l!l/2! n! 3.22 k0 0≤l≤n−k l≡0 mod 2 From Theorem 3.4, we note that Hn x n! n−1 k0 0≤l≤n−k l≡0 mod 2 10 Discrete Dynamics in Nature and Society Thus, we have, for 0 ≤ k ≤ n − k, 0≤l≤n−k l≡0 mod 2 Hn−k−l 0. n − k − l!l/2! 3.23 Let l, k ∈ Z with k ≤ l. Then we easily see that ∞ −∞ ∞ −∞ dk e−x dxk 2 dk e−x dxk √ Bl xdx −1k l! π Bl−k−j , l − k − j !2j j/2 ! 3.24 El−k−j . l − k − j !2j j/2 ! 3.25 0 ≤ j ≤ l−k j ≡ 0 mod 2 2 √ El xdx −1k l! π 0≤j≤l−k j≡0 mod 2 Let us consider the following polynomial of degree n in Pn : px n Bk xBn−k x. 3.26 k0 From 3.6, we note that px can be rewritten as px n Ck Hk x, 3.27 k0 where −1k Ck k √ 2 k! π ∞ −∞ dk e−x dxk 2 pxdx. 3.28 In 15, it is known that px n Bk xBn−k x k0 n−2 2 n2 Bn−l Bl x n 1Bn x. l n 2 l0 3.29 From 3.23 and 3.29, we have the following: −1k Ck k √ 2 k! π ∞ k −x2 ∞ k −x2 n−2 d e d e 2 n2 Bl xdx n 1 Bn xdx , l n 2 l0 dxk dxk −∞ −∞ 3.30 Discrete Dynamics in Nature and Society 11 By 3.24 and 3.30, we get 2 dn e−x Bn xdx × n 1 Cn dxn −∞ √ n1 −1n n! πB0 −1n × 1 n , n √ 0 n 2 0!2 0! 2 n! π 2 ∞ dn−1 e−x −1n−1 Cn−1 Bn xdx × n 1 √ dxn−1 2n−1 n − 1! π −∞ ⎛ ⎞ n−1 1 ⎜ ⎟ B1−j √ −1 ×⎜ j ⎟ n 1−1n−1 n! π √ ⎝ n−1 2 n − 1! π 1 − j !2 j/2 ! ⎠ j0 −1n √ 2n n! π ∞ 3.31 j≡0 mod 2 −1n−1 √ 2n−1 n − 1! π −nn 1 √ × n 1−1n−1 n! πB1 . 2n For 0 ≤ k ≤ n − 2, we have Ck ∞ k −x2 ∞ k −x2 n−2 d e d e 2 n2 Bl xdx n 1 Bn xdx Bn−l l n 2 lk dxk dxk −∞ −∞ ⎧ ⎪ ⎪ n−2 Bl−k−j √ −1k ⎨ 2 n2 k √ Bn−l −1k l! π × j l n 2 2 k! π ⎪ ⎪ lk 0 ≤ j ≤ l−k l − k − j !2 j/2 ! ⎩ −1k k √ 2 k! π j≡0 mod 2 √ n 1−1k n! π 0 ≤ j ≤ n−k j≡0 mod 2 n−2 2 n 2 lk 0 ≤ j ≤ l−k j≡0 mod 2 n 1! ⎫ ⎪ ⎪ ⎬ Bn−k−j n − k − j !2j j/2 ! ⎪ ⎪ ⎭ Bn−l Bl−k−j l! n2 kj l 2 k! l − k − j ! j/2 ! 0 ≤ j ≤ n−k j≡0 mod 2 Bn−k−j . k! n − k − j ! j/2 !2kj 3.32 Therefore, by 3.27 and 3.32, we obtain the following theorem. 12 Discrete Dynamics in Nature and Society Theorem 3.5. For n ∈ Z , one has n Bk xBn−k x k0 ⎧ ⎪ n−2 ⎪ ⎨ n−2 n 2 l!Bn−l Bl−k−j 2 kj ⎪ l n 2 lk 0 ≤ j ≤ n−k 2 k! l − k − j ! j/2 ! k0 ⎪ ⎩ j≡0 mod 2 n 1! 0 ≤ j ≤ n−k j≡0 mod 2 − 2kj k! Bn−k−j ⎫ ⎪ ⎪ ⎬ 3.33 Hk x n − k − j ! j/2 ! ⎪ ⎪ ⎭ n1 nn 1 Hn−1 x n Hn x. 2n 2 Acknowledgment This research was supported by Basic Science Research Program through the National Research Foundation of Korea NRF funded by the Ministry of Education, Science and Technology 2012R1A1A2003786. References 1 H. Ozden, I. N. Cangul, and Y. Simsek, “On the behavior of two variable twisted p-adic Euler q-lfunctions,” Nonlinear Analysis, vol. 71, no. 12, pp. e942–e951, 2009. 2 S.-H. Rim, A. Bayad, E.-J. Moon, J.-H. Jin, and S.-J. Lee, “A new construction on the q-Bernoulli polynomials,” Advances in Difference Equations, vol. 2011, article 34, 2011. 3 C. S. Ryoo, “Some relations between twisted q-Euler numbers and Bernstein polynomials,” Advanced Studies in Contemporary Mathematics, vol. 21, no. 2, pp. 217–223, 2011. 4 Y. Simsek, “Construction a new generating function of Bernstein type polynomials,” Applied Mathematics and Computation, vol. 218, no. 3, pp. 1072–1076, 2011. 5 Y. Simsek and M. Acikgoz, “A new generating function of q- Bernstein-type polynomials and their interpolation function,” Abstract and Applied Analysis, vol. 2010, Article ID 769095, 12 pages, 2010. 6 Y. Simsek, “Generating functions of the twisted Bernoulli numbers and polynomials associated with their interpolation functions,” Advanced Studies in Contemporary Mathematics, vol. 16, no. 2, pp. 251– 278, 2008. 7 C. Vignat, “Old and new results about relativistic Hermite polynomials,” Journal of Mathematical Physics, vol. 52, no. 9, Article ID 093503, 16 pages, 2011. 8 T. Kim, “A note on q-Bernstein polynomials,” Russian Journal of Mathematical Physics, vol. 18, no. 1, pp. 73–82, 2011. 9 S. Araci, D. Erdal, and J. J. Seo, “A study on the fermionic p-adic q-integral representation on Zp associated with weighted q-Bernstein and q-Genocchi polynomials,” Abstract and Applied Analysis, Article ID 649248, 10 pages, 2011. 10 A. Bayad, “Modular properties of elliptic Bernoulli and Euler functions,” Advanced Studies in Contemporary Mathematics, vol. 20, no. 3, pp. 389–401, 2010. 11 A. Bayad and T. Kim, “Identities involving values of Bernstein, q-Bernoulli, and q-Euler polynomials,” Russian Journal of Mathematical Physics, vol. 18, no. 2, pp. 133–143, 2011. Discrete Dynamics in Nature and Society 13 12 L. Carlitz, “Note on the integral of the product of several Bernoulli polynomials,” Journal of the London Mathematical Society, vol. 34, pp. 361–363, 1959. 13 L. Carlitz, “Multiplication formulas for products of Bernoulli and Euler polynomials,” Pacific Journal of Mathematics, vol. 9, pp. 661–666, 1959. 14 L. Carlitz, “Arithmetic properties of generalized Bernoulli numbers,” Journal für die Reine und Angewandte Mathematik, vol. 202, pp. 174–182, 1959. 15 D. S. Kim, D. V. Dolgy, T. Kim, and S. H. Rim, “Some formulae for the product of two Bernoulli and Euler polynomials,” Abstract and Applied Analysis. In press. 16 T. Kim, “Some identities on the q-Euler polynomials of higher order and q-Stirling numbers by the fermionic p-adic integral on Zp ,” Russian Journal of Mathematical Physics, vol. 16, no. 4, pp. 484–491, 2009. 17 H. Y. Lee, N. S. Jung, and C. S. Ryoo, “A note on the q-Euler numbers and polynomials with weak weight α,” Journal of Applied Mathematics, vol. 2011, Article ID 497409, 14 pages, 2011. 18 H. Ozden, “p-adic distribution of the unification of the Bernoulli, Euler and Genocchi polynomials,” Applied Mathematics and Computation, vol. 218, no. 3, pp. 970–973, 2011. 19 T. Kim, J. Choi, Y. H. Kim, and C. S. Ryoo, “On q-Bernstein and q-Hermite polynomials,” Proceedings of the Jangjeon Mathematical Society, vol. 14, no. 2, pp. 215–221, 2011. 20 K. Coulembier, H. De Bie, and F. Sommen, “Orthogonality of Hermite polynomials in superspace and Mehler type formulae,” Proceedings of the London Mathematical Society. Third Series, vol. 103, no. 5, pp. 786–825, 2011. 21 H. Chaggara and W. Koepf, “On linearization and connection coefficients for generalized Hermite polynomials,” Journal of Computational and Applied Mathematics, vol. 236, no. 1, pp. 65–73, 2011. 22 H. E. J. Curzon, “On a connexion between the functions of Herimite and the functions of Legendre,” Proceedings of the London Mathematical Society, vol. 12, no. 1, pp. 236–259, 1913. 23 S. Fisk, “Hermite polynomials,” Journal of Combinatorial Theory. Series A, vol. 91, no. 1-2, pp. 334–336, 2000. Advances in Operations Research Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Advances in Decision Sciences Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Mathematical Problems in Engineering Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Journal of Algebra Hindawi Publishing Corporation http://www.hindawi.com Probability and Statistics Volume 2014 The Scientific World Journal Hindawi Publishing Corporation http://www.hindawi.com Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 International Journal of Differential Equations Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Volume 2014 Submit your manuscripts at http://www.hindawi.com International Journal of Advances in Combinatorics Hindawi Publishing Corporation http://www.hindawi.com Mathematical Physics Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Journal of Complex Analysis Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 International Journal of Mathematics and Mathematical Sciences Journal of Hindawi Publishing Corporation http://www.hindawi.com Stochastic Analysis Abstract and Applied Analysis Hindawi Publishing Corporation http://www.hindawi.com Hindawi Publishing Corporation http://www.hindawi.com International Journal of Mathematics Volume 2014 Volume 2014 Discrete Dynamics in Nature and Society Volume 2014 Volume 2014 Journal of Journal of Discrete Mathematics Journal of Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Applied Mathematics Journal of Function Spaces Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Optimization Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Volume 2014