Ehrhart拟多项式与平移变换
Ehrhart quasi-polynomials and parallel translations
AI总结:
该研究针对有理多面体平移后的Ehrhart拟多项式求解问题,提出基于环面排列与平移锥格点计数的计算方法,证明相关拟多项式信息可在整数平移等价下确定多面体,并刻画了平移后拟多项式均对称的有理多面体特征。
摘要:
给定有理多面体$P \subset \mathbb R^d$,计数$P$的整数伸缩体中格点数量的数值函数是一个拟多项式,被称为$P$的Ehrhart拟多项式$\mathrm{ehr}_P$。本文研究如下问题:给定有理$d$维多面体$P \subset \mathbb R^d$,是否存在简便方法来获取所有平移体$P+\mathbf v$(其中$\mathbf v \in \mathbb Q^d$)的Ehrhart拟多项式?我们提出了一种利用某类环面排列(toric arrangement)以及$P$的平移锥格点计数函数来计算这类Ehrhart拟多项式的方法。该方法可直观展现$\mathrm{ehr}_{P+\mathbf v}$的组成多项式在环面$\mathbb R^d/\mathbb Z^d$中的变化规律。我们还证明,所有$\mathbf v \in \mathbb Q^d$对应的$\mathrm{ehr}_{P+\mathbf v}$信息,可在相差整数向量平移的等价意义下唯一确定有理$d$维多面体$P \subset \mathbb R^d$,并刻画了所有满足“对任意$\mathbf v \in \mathbb Q^d$,$\mathrm{ehr}_{P+\mathbf v}$均具有对称性”的有理$d$维多面体$P \subset \mathbb R^d$的特征。
英文摘要:
Given a rational polytope $P \subset \mathbb R^d$, the numerical function counting lattice points in the integral dilations of $P$ is known to become a quasi-polynomial, called the Ehrhart quasi-polynomial $\mathrm{ehr}_P$ of $P$. In this paper we study the following problem: Given a rational $d$-polytope $P \subset \mathbb R^d$, is there a nice way to know Ehrhart quasi-polynomials of translated polytopes $P+ \mathbf v$ for all $\mathbf v \in \mathbb Q^d$? We provide a way to compute such Ehrhart quasi-polynomials using a certain toric arrangement and lattice point counting functions of translated cones of $P$. This method allows us to visualize how constituent polynomials of $\mathrm{ehr}_{P+\mathbf v}$ change in the torus $\mathbb R^d/\mathbb Z^d$. We also prove that information of $\mathrm{ehr}_{P+\mathbf v}$ for all $\mathbf v \in \mathbb Q^d$ determines the rational $d$-polytope $P \subset \mathbb R^d$ up to translations by integer vectors, and characterize all rational $d$-polytopes $P \subset \mathbb R^d$ such that $\mathrm{ehr}_{P+\mathbf v}$ is symmetric for all $\mathbf v \in \mathbb Q^d$.
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