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arXiv 1402.0773math.CA
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关于离散正交多项式的差分导数的线性相关序列

On linearly related sequences of difference derivatives of discrete orthogonal polynomials

R. Alvarez-Nodarse, J. Petronilho, N. C. Pinzon-Cortes, R. Sevinik-Adiguzel

摘要:

设D_v为D_ωp(x)= \frac{p(x+ω)-p(x)} ω定义的差分算子,D_qp(x)= \frac{p(qx)-p(x)}{(q-1)x}定义的q-差分算子.设U和V是两个矩正则线性泛函,(Pn)n和Q n是它们对应的正交多项式序列(OPS).本文讨论了离散正交多项式理论中涉及这两种OPS的一个反问题,假定它们的高阶m和k的差分导数$D_ν$分别为通过线性代数结构关系连接,例如$$ \sum_{i=0}^M a_{i,n} D_ν^m P_{n+m-i}(x) = \sum_{i=0}^N b_{i,n} D_ν^k Q_{n+k-i}(x), \quad n\geq 0, $$,其中$M,N,m,k= 0,1,2,.在一定的条件下,我们证明了U和V是由一个合理的因素(在分配意义上)。而且,当m \neq k时,U和V都是D_v-半经典泛函.这就引出了(M,N)-D_v-相干对的概念,并将以前的一些工作推广到离散情形。作为一个应用,我们考虑OPS关于一定以下Sobolev型离散内积。

英文摘要:

Let D_v the difference operator and q-difference operators defined by D_ωp(x) = \frac{p(x+ω)-p(x)}ω and D_q p(x) = \frac{p(qx)-p(x)}{(q-1)x}, respectively. Let U and V be two moment regular linear functionals and let (P_n)_n and Q_n)_n be their corresponding orthogonal polynomial sequences (OPS). We discuss an inverse problem in the theory of discrete orthogonal polynomials involving the above two OPS assuming that their difference derivatives $D_ν$ of higher orders m and k (resp.) are connected by a linear algebraic structure relation such as $$ \sum_{i=0}^M a_{i,n} D_ν^m P_{n+m-i}(x) = \sum_{i=0}^N b_{i,n} D_ν^k Q_{n+k-i}(x), \quad n\geq 0, $$ where $M,N,m,k=0,1,2,... Under certain conditions, we prove that U and V are related by a rational factor ç (in the distributional sense). Moreover, when m\neq k then both U and V are D_v-semiclassical functionals. This leads us to the concept of (M,N)-D_v-coherent pair of order (m,k) extending to the discrete case several previous works. As an application we consider the OPS with respect to a certain following Sobolev-type discrete inner product.

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