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arXiv 0904.2602math-phmath.MP
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柯西双正交多项式

Cauchy Biorthogonal Polynomials

M. Bertola, M. Gekhtman, J. Szmigielski

摘要:

本文研究了某些双正交多项式在一个特定的同时Hermite-Pade逼近格式中的性质。结合任意正核和正轴上的一对正测度,定义了双正交多项式,并证明了它们的零点是单正的。然后,我们专门的内核柯西内核1/{x+y},并表明,随后的双正交多项式解决四项递归关系,有相关的Christoffel-Darboux广义公式,和他们的零交错。此外,这些多项式还解决了二阶Nikishin系统的Hermite-Pade逼近问题的组合。动机来自两个遥远的地区;一方面,在研究的逆谱问题的峰值解的Degasperis-Procesi方程;另一方面,从随机矩阵模型,涉及两个正定随机厄米矩阵。最后,我们展示了如何刻画这些多项式的一个黎曼-希尔伯特问题。

英文摘要:

The paper investigates the properties of certain biorthogonal polynomials appearing in a specific simultaneous Hermite-Pade' approximation scheme. Associated to any totally positive kernel and a pair of positive measures on the positive axis we define biorthogonal polynomials and prove that their zeroes are simple and positive. We then specialize the kernel to the Cauchy kernel 1/{x+y} and show that the ensuing biorthogonal polynomials solve a four-term recurrence relation, have relevant Christoffel-Darboux generalized formulae, and their zeroes are interlaced. In addition, these polynomial solve a combination of Hermite-Pade' approximation problems to a Nikishin system of order 2. The motivation arises from two distant areas; on one side, in the study of the inverse spectral problem for the peakon solution of the Degasperis-Procesi equation; on the other side, from a random matrix model involving two positive definite random Hermitian matrices. Finally, we show how to characterize these polynomials in term of a Riemann-Hilbert problem.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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