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arXiv 1302.7116math.RTmath.CA
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轨道测度、Gelfand-Tsetlin多面体和样条的投影

Projections of orbital measures, Gelfand-Tsetlin polytopes, and splines

Grigori Olshanski

摘要:

酉群U(N)通过共轭作用在N × N埃尔米特矩阵的空间H(N)上,并且该作用的每个轨道都携带唯一不变的概率测度,称为轨道测度。考虑空间H(N)在实直线上的投影,给埃尔米特矩阵分配其(1,1)-元。在这个投影下,一般轨道测度的前推密度是一个具有N个节点的样条函数。这个事实是由Andrei Okounkov在1996年指出的,本文的目标是提出一个多维推广。也就是说,如果我们切掉任意大小KxK的矩阵左上角,而不是(1,1)项,其中K=2,.,N-1,则一般轨道测度的前推仍然是可计算的:它的密度由一维样条组成的KxK行列式给出。这个结果也可以用Gelfand-Tsetlin多面体的投影来表示。

英文摘要:

The unitary group U(N) acts by conjugations on the space H(N) of NxN Hermitian matrices, and every orbit of this action carries a unique invariant probability measure called an orbital measure. Consider the projection of the space H(N) onto the real line assigning to an Hermitian matrix its (1,1)-entry. Under this projection, the density of the pushforward of a generic orbital measure is a spline function with N knots. This fact was pointed out by Andrei Okounkov in 1996, and the goal of the paper is to propose a multidimensional generalization. Namely, it turns out that if instead of the (1,1)-entry we cut out the upper left matrix corner of arbitrary size KxK, where K=2,...,N-1, then the pushforward of a generic orbital measure is still computable: its density is given by a KxK determinant composed from one-dimensional splines. The result can also be reformulated in terms of projections of the Gelfand-Tsetlin polytopes.

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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