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arXiv 1407.8323nlin.SIhep-thmath-phmath.MP
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Hurwitz数与BKP层次

Hurwitz numbers and BKP hierarchy

S. M. Natanzon, A. Yu. Orlov

摘要:

本文研究由整数$\textsc{f}\ge 0$和$\textsc{e} \le 2$以及$3k$参数集$n_i,q_i,t_i,\,i=1,..., k$定义的Schur函数的特殊比级数.这些级数可以用矩阵积分的形式表示。在$k=0$的情况下,这些系列生成Hurwitz数的$d$ -折叠分支覆盖的连接表面与一个给定的欧拉特征$\textsc{e}$和任意配置文件在$\textsc{f}$分歧点。如果$k>0$,则它们生成Hurwitz数与分布在由$i=1,...,k$索引的颜色组之间的附加分歧点的加权和,权重根据参数$n_i,q_i,t_i$来写。通过指定参数,我们得到了具有$\textsc{f}$任意固定轮廓的所有Hurwitz数的和,以及满足以下条件的附加轮廓:轮廓长度和和每个色组中的分歧点的数目都是给定的。在$\textsc{e}=\textsc{f}=1,2$的情况下,该系列可以用Kac和van de Leur的BKP tau函数来识别,该函数具有称为超几何tau函数的特殊类型。${\mathbb{RP}}^2$的$d$ -折叠分支覆盖的Hurwitz数之和与单组分BKP层次相关。我们还将Hurwitz数的和与胖图的单矩阵模型联系起来.

英文摘要:

We consider special series in ratios of the Schur functions which are defined by integers $\textsc{f}\ge 0$ and $\textsc{e} \le 2$, and also by the set of $3k$ parameters $n_i,q_i,t_i,\,i=1,..., k$. These series may be presented in form of matrix integrals. In case $k=0$ these series generates Hurwitz numbers for the $d$-fold branched covering of connected surfaces with a given Euler characteristic $\textsc{e}$ and arbitrary profiles at $\textsc{f}$ ramification points. If $k>0$ they generate weighted sums of the Hurwitz numbers with additional ramification points which are distributed between color groups indexed by $i=1,...,k$, the weights being written in terms of parameters $n_i,q_i,t_i$. By specifying the parameters we get sums of all Hurwitz numbers with $\textsc{f}$ arbitrary fixed profiles and the additional profiles provided the following condition: both, the sum of profile lengths and the number of ramification points in each color group are given numbers. In case $\textsc{e}=\textsc{f}=1,2$ the series may be identified with BKP tau functions of Kac and van de Leur of a special type called hypergeometric tau functions. Sums of Hurwitz numbers for $d$-fold branched coverings of ${\mathbb{RP}}^2$ are related to the one-component BKP hierarchy. We also present links between sums of Hurwitz numbers and one-matrix model of the fat graphs.

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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