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Mathematics
Sobolev orthogonal polynomials generated by Meixner polynomials
I. I. Sharapudinovabc,
Z. D. Gadzhievaab a Dagestan Scientific Center RAS
b Dagestan State Pedagogical University, 45, M.Gadzhieva st., 367032,
Makhachkala, Russia
c Vladikavkaz Scientific Center RAS
Abstract:
The problem of constructing Sobolev orthogonal
polynomials
$m _{r,n}^{\alpha}(x,q)$ $(n=0,1,\ldots)$, generated
by classical Meixner's polynomials is considered. They can by
defined using the following equalities
$m_{r,k}^{\alpha}(x,q)={x^{[k]}\over k!}$,
$x^{[k]}=x(x-1)\cdots(x-k+1)$,
$k=0,1,\ldots,r-1$,
$m_{r,k+r}^{\alpha}(x,q)=\frac{1}{(r-1)!}\sum\limits_{t=0}^{x-r}(x-1-t)^{[r-1]}m_{k}^{\alpha}(t,q)$,
where
$m_{k}^{\alpha}(t,q)$ denote Meixner's polynomial of degree
$k$, orthonormal on
$\Omega=\{0,1,\ldots\}$ with weight
$\rho(x)=q^x\frac{\Gamma(x+\alpha+1)}{\Gamma(x+1)}(1-q)^{\alpha+1}$.
Polynomials
$m _{r,n}^{\alpha}(x,q)$,
$(n=0,1,\ldots)$ are
orthonormal on
$\Omega=\{0,1,\ldots\}$ with respect to the inner
product
$$
\langle m_{r,n}^{\alpha},m_{r,m}^{\alpha}\rangle=
\sum\limits_{k=0}^{r-1}\Delta^km_{r,n}^{\alpha}(0,q)\Delta^km_{r,m}^{\alpha}(0,q)+
\sum\limits_{j=0}^{\infty}\Delta^rm_{r,n}^{\alpha}(j,q)\Delta^r
m_{r,m}^{\alpha}(j,q)\rho(j).
$$
For
$m_{r,n}^{\alpha}(x,q)$ we obtain the explicit formula that
contains the Ìeixner polynomial
$M_{n}^{\alpha-r}(x,q)$:
$$
m_{r,k+r}^{\alpha}(x,q)=\big(\frac{q}{q-1}\big)^r\left\{h_{k}^{\alpha}(q)\right\}^{-1/2}
\left[M_{k+r}^{\alpha-r}(x,q)-\sum\limits_{\nu=0}^{r-1}\frac{A_{r,k,\nu}x^{[\nu]}}{\nu!}\right],
k=0,1,\ldots,
$$
where $A_{r,k,\nu}=\Big({q-1\over q}\Big)^\nu
\frac{\Gamma(k+\alpha+1)}{(k+r-\nu)!\Gamma(\nu-r+\alpha+1)}$, $M_n^\alpha(x,q)=\frac{\Gamma (n+\alpha+1)}{n!}
\sum_{k=0}^n{n^{[k]}x^{[k]}\over \Gamma
(k+\alpha+1)k!}\left(1-{1\over q}\right)^k$, $h_n^\alpha(q)=
{n+\alpha\choose n}q^{-n}\Gamma(\alpha+1)$.
Key words:
orthogonal Sobolev polynomial, Meixner polynomials orthogonal on the grid, approximation of discrete functions, mixed series in Meixner polinomials orthogonal on a uniform grid.
UDC:
517.587
DOI:
10.18500/1816-9791-2016-16-3-310-321